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Comment by nine_k | Hacker News Reader

I suppose the same should apply to hybrid cars, which outnumber pure EVs significantly [1]. The effect comes from converting the kinetic energy back to the battery charge via generation instead of wasting it via friction, which is the whole point of hybrids.

[1]: https://www.consumeraffairs.com/automotive/how-many-electric...

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which is the whole point of hybrids

Part of the point, not the whole point. Regenerative breaking is absolutely a win; but there can also be a significant benefit from allowing the ICE to remain in the RPM "sweet spot" rather than moving around a larger range.

Another part of the point is that you can pack a much smaller and more efficient ICE and then substitute the missing power and torque from electric motors when needed. Most cars are not used at max power all the time. You need max power only at short times when accelerating. With pure ICE there is the tradeoff - a bigger engine will get you more max power / max torque but is going to be less fuel efficient because of internal friction.

On paper, yes, but did that ever happen? Sorry for being sarcastic, but where I live the frugal hybrid is exceptionally rare and the "same big engine, but driving a much heavier car" hybrid is omnipresent. The kind of people who might buy the frugal one buy second or third hand while almost all buyers of factory new pick the "same big engine" option, and those are the ones who decide what's available on the second hand market.

Yes, every single prius for example? The biggest engine that was produced with seems to be a ~100 bhp engine which isn't much for a 1.5 metric tonne car

In most countries, yes. Despite the push for SUV-styled cards (which are heavier than a regular city car, but not by that much), engines have been small.

Toyota Yaris - HSD - 1.5L 4cyl Renault Clio - E-Tech - 1.6L Hyundai Kona (SUV) - 1.6L Honda Jazz - 1.5L Peugeot 208 - 1.2L Peugeot 3008 (SUV) - 1.6L Peugeot 5008 (Family SUV) - 2L And the list goes on. Even BMW with it's xDrive puts out 1.5L engines.

Huge engines are only common in two places: sports cars (and even then, only a specific category like AMGs and friends, because even a Porsche 992 only has a 3L engine) and the US.

The info is useful, but those do not seem to be all that small. There were smaller engines available for the ICE version of the Clio, for example.

There was, and it was shit. The Cléon-Fonte, despite all my love for its BBBBRRRRRRRRRRVVVVVVVVVVV was becoming wildly insufficient for the already ever heavier cars simply due to electronics and safety measures, and it was already a 1.2L. The smallest ever put on a Clio was a .999L, and anyone driving a Twingo knows how it behaves the moment there's... a slight incline, or two people in the care.

1.5L is an incredibly small engine, especially when previous versions required much larger. The Renault Scénic IV is a 1.5 ton brick that is happily running on a 1.2L engine. The Scénic II's most sold motorization was a 2L engine.

I feel like I remember a pickup being available that was a 6L v8. So one cylinder in that engine had almost the same volume as all the cylinders in a 1.5L engine combined. That's pretty crazy to me.

edit: oh it was mine heh, my first car was a 1979 ford with a 460 ( 7.5L v8 ). It was a hand me down from my grandfather, he said if i could get it running i could have it.

A 6 liter 4-cylinder would have the same volume in a single cylinder as a 1.5L engine. A V8 of that size would have half the volume in a single cylinder, not almost the same volume.

A 1.5 liter is incredibly small. You’ll struggle to accelerate up slight inclines with that. If you’re in the mountains it will be even worse.

Fiat 500 hybrid 999cc engine, 69bhp (51kW).

I hired one on holiday and it worked fine. Maybe I'm getting old but I see less point in getting something that does 0-60 in 4 sec when most traffic goes from 0-40 in about two minutes and doesn't get much faster. It still has a top speed over 100mph.

Omoda 9 (SUV) is sold in Europe only as plug-in hybrid with small-ish 1.5L 143HP engine + 394HP electric (145km of pure electric range, 35kWh LFP battery).

https://en.wikipedia.org/wiki/Exeed_Yaoguang

The vast majority of hybrids use simulated atkinson cycle... while their cylinders might be the same size as N/A vehicles, they leave the intake valve open past the end of the stroke, so they effectively are displacing less, even though the cylinder dimensions might be the same size. The advantage is that atkinson cycle is more efficient. But it has too poor performance characteristics for an ICE-only car.

>On paper, yes, but did that ever happen?

Like absolutely, unless you consider 1.4L petrol engine large for something with over 170KW (over 220hp). Such kind of offerings are quite common at the East side of the pond.

I'd consider engines with HP in the two digits range not big. Few ICE cars (hybrid or not) are ever accelerated at the rate you could achieve with a 75 HP engine revved into the high but still safe range. People buy big engines so that they can get all their acceleration needs served at half throttle. And that's for stick shifting, those on automatic pick engine size so that they can accelerate on quarter throttle or else the car shifts back and it sounds all x "small engine working hard" (which would be so much less inefficient!).

Our family owned a Mercedes 240D (71 peak horsepower at sea level) for many years. That car's performance was lackluster on a good day and trying to merge onto the Pennsylvania Turnpike (with very short acceleration lanes) was IMO quite unsafe. From that experience, I'm pretty sure that people are dipping into more acceleration than that car could ever muster.

I have no doubt that some people behave as you describe, but I think some of that is driven from a rational position of not wanting to buy a car that is incapable of anything more than their normal daily driving. If you need to accelerate quickly to merge safely into traffic, bringing only 75 [or 71] peak horsepower to the table isn't a comfortable position to be in.

Hybrid one - 0-100km/h sub 7sec. The most important part is not 0-xxx but being able to take trucks in relatively short distances b/c most roads features just two lanes. Pressing pedal to the metal and engaging both engine does that.

The sub 100 power doesn't mean much if the engine has a turbine, e.g. TSI of volkswagen

Yes, check out BYD's hybrids. The petrol engine is 46% efficient, which is pretty damn amazing. This is more efficient than most power plants (combined cycle plants are better- but most power plants are not combined-cycle).

So what is the well to wheel efficiency of this vs. pure electric? There are fuel transportation losses in one, and transmission line losses in the other. In many cities electricity is quite a bit more expensive than gas so hybrids are a better deal financially.

Which cities are those? I can think of maybe a few in the Middle East with subsidized gasoline, but I’m coming up blank after that.

> did that ever happen?

In 2010 with the Chevrolet Volt.

Which only had a 1.4l engine. It was not as efficient as the gas only Prius but could be more efficient overall as the Volt of 2010 had a 40 mile EV range.

I think the question is "is that overall effect the reality, or do most people buy a very heavy hybrid?"

I wonder whether people actually understand that they need a smaller engine for the same performance?

Despite my overall low estimation of people's ability to fluidly reason about engineering tradeoffs, I think they generally do understand this one well enough, at least for the decisions that they will face. They're only deciding which car to buy, not what engine specifications are required to make a car successful in the market.

They go test-drive cars, probably glance at performance specifications and/or read/watch a test drive review of the cars. They can look at the 0-60mph/0-100 kph times and get a feel for "this car will be able to get out of its own way" vs "this car will be a rolling roadblock".

So "actually understand"? Maybe not, but "understand enough to guide their purchasing decision?" and therefore enough for the actual automobile product teams to design to accommodate? I think they do.

I've never seen a car where the hybrid and pure gas versions have the same size engine; the hybrid engine is almost always lighter and makes less power.

There’s a few luxury cars that use the same or larger engines for the hybrid. Lexus did it with the LS, hybrid 600h had a larger engine (5L) than the gas 460 (4.6L).

Those are super rare though.

Dunno if you consider plugin hybrids hybrids, but I believe the Audi Q5 PHEV and ICE-only engines are the same.

BMW i8

This reminds me of the short lived dilbert cartoon when Dilbert is complaining about how pokey his Prius, and when he hands the car over to Dogbert, he somehow is able to rip out of the parking lot at high speed.

Seriously though, hybrids seem like a bad compromise to just getting an EV. Hybrids have an electric drive train with an ICE drive train, and somehow that double complexity will be worth it? In the long run, EVs are winning on cost alone (especially in China where making cheap EVs is a thing).

And, you can make much lighter and lower range electric cars without all those heavy batteries, and boost the range with diesel when needed. Very attractive in principle. Most cars are not using their full range all the time, for a lot of people a 50 mile range car would be more than enough 98% of the time, but that remaining 2% means that people end up buying 200 mile range cars instead.

But then, do you end up removing enough battery weight to offset the weight of a whole ICE?

I thought about PHEV but in the end went full EV simply because it seemed to me with two whole power trains that's 2x the components to go wrong/need maintenance.

That's a common misconception, but hybrids are almost never as complicated as an ICE powertrain plus an EV powertrain. E.g. most hybrids are able to eliminate many parts that ICE vehicles require, like, starters, drive belts, multi-ratio transmissions, alternators, etc. Because of this, many hybrids surpass ICE-only vehicles in reliability.

That same insight applies to regular hybrids, and yet Toyota’s hybrids are legendary for their durability. There’s a reason half the cabs where I live are Prius station wagons, and it’s not their efficiency, judging by how they’re driven.

Consumer reports found that HEV's were the most reliable, and PHEV"s the least reliable. That's nonsensical, there's little difference between the two.

Toyota is the biggest seller of HEV's, Stellantis of PHEV. That's the difference. EV's on paper should be the most reliable, but Tesla is the biggest seller of those. If you want reliability, choose by brand rather than engine type.

I was comparing a Hyundai Ioniq EV with a Hyundai Ioniq PHEV and was surprised to find more problems reported by the owners of the Ioniq EV.

Mostly issues with 12V battery, it seemed like.

In the end I bought a Stellantis EV so I probably deserve everything I get - but they are cheap!

12V batteries dying in EVs has been a consistent problem. I think it got better for Tesla when they moved from lead acid to lithium ion for the 12V (like the much bigger battery).

>Consumer reports found that HEV's were the most reliable, and PHEV"s the least reliable. That's nonsensical, there's little difference between the two.

Eh, it's not so much nonsensical, as it is that you're just misinterpreting the data.

This conversation here is specifically about powertrain reliability, but that isn't what consumer reports measures. They measure complaints about any feature on the vehicle, including ancillary accessories unrelated to the vehicle's ability to transport people.

But also as you point out, shitty engineering (Stellantis's specialty) is a bigger issue than any particular drivetrain type.

Toyota's success with the Prius proves that this fear is unfounded. You will regularly find second hand prius models for sale with 500,000 km on the odometer.

Just think - if two drivetrains were less reliable, wouldn't you see that with the Prius?

You're right in principle, but it's important to remember that tradeoffs exist. You can very much trade off engineering effort and time to improve reliability.

Commercial aviation is a great example of taming extreme inherent unsafety of aircraft by applying a lot of resources to the engineering side. Another is space programs.

And car power trains have nothing on those ;) As Toyota has shown, it's totally possible to make reliable hybrid cars with enough engineering thrown at the problem.

So if all things were equal, you'd absolutely expect an EV to be more reliable than a hybrid, but all things are rarely equal.

In some ways it’s more complicated. The battery management and cooling is a point of failure. It’s also heavier and so wear and tear on suspension is greater.

On the other hand, a Toyota hybrid doesn’t have a gearbox at all, not even a CVT. Instead it has something similar to a differential, it’s mechanically simple and very reliable. It uses the electric motor in place of a turbo, so that’s another common failure point removed. It doesn’t have a starter motor, and the Atkinson cycle engine should suffer less stress than an equivalent petrol.

Practically the biggest problem is finding a 3rd party garage who will inspect the hybrid parts as part of a service.

This. This times 100x . Also, it’s not like each powertrain has an independent failure mode. If either break, your car is a brick until it’s fixed.

I have a friend who drives a Chevy Volt with a dead ICE engine; she just charges the battery and uses it as a (rather short range) pure EV vehicle. Not ideal, but it works for her until she gets something else.

If she was in California she wouldn't be able to pass smog at her next inspection, which is a funny problem considering she drives in pure EV mode now.

Oh I agree completely. I'm driving an old diesel now but I have no desire to get a hybrid, I'd get a pure EV if I were to buy a new car. But there are some tempting things in principle about plug-in hybrids

Smaller cars have always been available, but people have shown a preference for bigger cars where they can sit higher up, even though it costs them more.

I'm not talking about size, I'm talking about range and weight. You can have a huge car or a smaller car, going from a 90kWh battery pack to a 30kWh battery pack is gonna have the same weight saving in both

Maybe they should be at least charged for the catastrophic externalities that that "preference" results in.

does "preference" equate to endless, manipulative advertising from car manufacturers? Or, perhaps, the "preference" of higher profit margins from larger cars, pushing manufacturers to entirely abandon reasonably sized cars?

"Everyone who doesn't want what I want them to want has been brainwashed by corporate interests" is not a robust assertion under even the most casual scrutiny.

I hate to break it to you but something like a Rogue or HRV does circles around an Altima or Civic when it comes to daily flexibility and utility for a fairly paltry additional cost. It doesn't take a degree in rocket surgery to figure out why they fly off the shelves. For the average person they're a good combination of attributes.

The North American market now only includes a handful of sedans. Meanwhile, Hyundai and Toyota somehow manage to sell “tiny” cars in Korea, Japan and lots of developing countries.

A practical car is a station wagon, not an SUV, many of which have less storage space.

Please, cut the needless snark. People do buy vehicles for edge cases but the lack of smaller, practical vehicles is driven is large part by manufacturer profit.

Many of those tiny foreign cars are unfortunately not economically useful to sell in the regulated markets of the rich west, and even when they are they often aren't without the developing nation sales volume to amortize a lot of the fixed costs over.

I agree that there's a lot of stupidity going on when it comes to station wagons vs crossovers vs compact SUVs and the OEMs really do SUV-ify a lot of things that ought not to be.

The shape of these vehicles is fairly preordained by the nature of the fuel economy regulations and wind resistance and other regulations that apply equally to all of them. You're not gonna find "more space" in something like a Subaru Outback by squashing it on the vertical axis unless you stretch it in another dimension or find somewhere else to find space. Maybe you might be able to eek out a slightly better angle on the hatch or something but it ain't gonna be much. Fuel economy regulations make cars with thicc asses like the big sedans and station wagons of yesterday nonsensical.

The snark is not needless. It is tautologically impossible for the overwhelming majority of people do be "doing it wrong" on a matter that is in large part a subjective one of preference. If someone wants to assert that then I will talk down to them.

People buy these small SUVs left and right because they're seemingly the best option when it comes to well rounded boring A to B vehicles.

I think the crossover is pretty much the modern station wagon. I suppose they get marketed as SUV's but they're basically just a bit longer and taller car vs what I'd consider a "real" SUV; an enclosed truck chassis.

also once everybody else is obstructing your view with a bigger car it becomes necessary to have a bigger one, it's a race to the metaphorical bototm

This is the thing with good hybrids.

The "gas pedal" becomes a "I want to go faster/slower" pedal, its position has zero impact on the RPM.

As an anecdote: A security company I know only buys Toyota Hybrids for their guards just because of that. They have a habit of driving cars like they stole them and normal ICE cars break down from that kind of abuse. Hybrids won't let you abuse them, they pick the RPM and you deal with it.

(They also swap the passenger seat for a plastic box because the guards threw heavy crap like safety boxes on it, wearing down the seat in months)

This is less a hybrid thing and more a new transmission thing. It, of course, isn't free. The efficiency of a CVT is a good 10-20 percent lower than previous transmissions. That said, currently, the win from keeping the engine at either the max power or the max efficiency speed is substantial.

There are some really good videos out there going over how newer CVTs work. Looks like some people are working on ones that are teeth driven, to reduce the loss from being free belt driven. Borderline magical stuff, all told. (Obviously, not magic magic. But very very impressive designs.)

The post you commented on was talking about Toyota hybrids though, who don't use a CVT in the sense you're talking about.

They use a series-parallel hybrid transmission which is sometimes called eCVT, but works completely different from a classic CVT. There are no pullies, belts, chains, none of that. What they do have is a couple of motor-generators and a differential to link the system up with the engine and the drive shaft. No friction losses like CTVs have.

See https://prius.ecrostech.com/original/PriusFrames.htm, or look up "Hybrid Synergy Drive" on Wikipedia or Youtube or your favorite search engine.

Ah, totally fair in that this particular transmission is better than the belt driven CVT stuff. I had thought they were still a bit worse than other transmissions, but it looks like if they are, it is on the order of 1% or so.

Is fascinating to watch these things work.

I have a Subaru (ten years old w/ >200k miles on it's chain-type CVT), and I thought the justification for it was that it was more efficient than previous systems.

From a mechanical engineering standpoint, the Subaru CVT uses a fairly conventional lock-up torque converter at the input, but that gets locked as you pass something like 15-20 mph (once the lowest gear ratio is satisfactory w/o the torque converter function) and beyond that all shifting of the CVT is done w/ the torque converter locked. In addition, the clamping force of the sheaves is adjusted per the torque load of the transmission to minimize the frictional losses.

Anyway I'm curious about data comparing efficiency of conventional and CVT automatics.

My understanding is that the overall system is more efficient. It is only the transmission that is less so.

The videos online that look at various CVT systems is truly an amazing resource that I regret not having when I was younger. :D

If overall efficiency is what you see reflected in the EPA mileage numbers (or similar European tests), in what scenario would a lower efficiency transmission (lower Pout/Pin over some range of operating points?) lead to or even allow better overall efficiency?

I'm not sure I understand the question? You get the engine to hit its sweet spot and to hold it there. That gain outweighs the loss from the new transmission.

This would be similar to hitting the optimal torque point. The idea there would be that you can get out of the acceleration phase faster, so that you can transition to a more efficient gear to maintain the speed for longer.

The wikipedia looks to cover this well. One of the cites is specific on the efficiency of the CVT. I think I overstated how much higher the loss is, so maybe that is confusing things? I thought it was 10-20, but the cite on the page shows it solidly around 10.

Ah, thank you, I see the argument. I'm still a bit skeptical though when many non-CVT automatics are 6 or 8-speed models that there would be much "sweet spot" benefit left by being able to make relatively small changes in engine speed. Like many things probably depends on exactly what comparison is being made.

I mean, we are comparing 6-8 to effectively infinite? Question then comes into just how much is lost by being outside of the sweet spot for an engine. Which, I agree that I would not have thought it would be that big of a deal. Just going off modestly paying attention in my car, I see massive benefits keeping the car around 300 rpms lower.

Interestingly, my car gets better gas mileage around the 40ish speeds than I do at full highway speeds. That somewhat surprises me. It is very dependent on not having a heavy foot, of course.

Best efficiency speed can be understood by considering impact of fixed losses like HVAC, lights, computing, which consume more energy the longer you drive (so the total energy for those would be minimized by going faster) and the aerodynamic losses in which force goes with speed squared, power w/ speed cubed, energy over a fixed distance back to squared because at higher speeds time is reduced (this component is theoretically minimized by going very slowly). In between is rolling resistance which requires a fixed energy per distance, so it doesn't care about speed.

For EVs, the drivetrain efficiency is so high that it's variability with operating point doesn't affect this calculation much, and so the most efficient speed of an EV is around the speed at which the fixed losses equal the aero ones. This will vary greatly with environmental conditions since AC or heating load can be large in hot or cold conditions but at the right temperature will go to near zero.

In ICE cars, the drivetrain efficiency is much lower and so the drivetrain efficiencies are a much more significant part of the optimization problem, but the basic physics of the aerodynamics are the same.

The model I used to use in my head is that for an ICE, the most efficient operating point is probably around the lowest speed the car can operate in the highest gear, so maybe around 40 mph / 60 km/h? Obviously a rough heuristic though.

Generally speaking your car will get better fuel economy at 40mph than it will at 60 or 70mph. Your car gets so much more wind resistance the faster you go.

The main reason why city mileage is usually lower is because of all the stopping.

I think I just mentally had this idea shifted up about 10-15 mph. I'd expected 55 to be the sweet spot, for some reason.

Do all Toyotas do that? I'm pretty sure that my dad's Corolla will rev the engine when I press the gas if the engine is already running.

I'm also surprised for the first few minutes when I drive it how little "engine braking" it has (my habit is from riding a big motorbike).

Depends on the configuration. If they are equipped with a CVT+electric engine on the shaft, then that's the case: they rev to the sweet spot (which on gas engines is 4000-5000 rpm on acceleration? Depending on expected engine load I assume) and the speed is controlled by hydraulic force applied on the CVT.

With other hybrids: depends on the generator they have installed, but it matches the consumption in amps by the engine in order to "go" if it is not directly coupled with the transmission, or they just downshift to accelerate with help of the electric engine.

I am assuming a lot here: Toyotas (specially RAV4) mount CVTs among others, assuming pure electric generator by the ICE or coupled to it... So it depends a lot on specific configuration.

Even CVTs will rev the engine if you floor it, no? They typically allow for wanting to be in a few sweet spots. I prefer to keep it near the max efficiency speed. That said, my wife is a bit more aggressive and spends more time in the max power mark. It has a predictable change on the MPG reported by the vehicle.

I know for a fact you can neutral-drop a prius.

I know it's not exactly the same, but I was a teenager and curious, and you can rev them and shift into drive with some heel-toe finesse. Not sure if this works on the newer ones, this one was an early 2010s model.

Thank you for performing the experiment I didn’t even know I wanted to know the results of before now.

I performed many experiments on that family prius and with complete honestly, my experiments weren't even in the top ten worst things that car survived.

Trees, multiple motorcycles, final destination esque road debris, an accident that should have totalled it if not for an insurance mistake, leading to repairs worth more than the car. Three teenage drivers and two adult drivers with heavy feet. Not to mention many many hardware store runs hauling various sacks of yard materials, baby trees, lumber, etc.

My favorite times were rallying on compacted un-plowed snow. The thin tires and light weight meant it absolutely shredded.

It's my opinion that the Toyota Prius is one of the greatest vehicles ever built and they should be respected and feared.

That's an amazing testimony to its grit. I could stand to hear more of those stories over the appropriate beverage.

Dunno. My both Priuses did it and the company was specifically using the Yaris Hybrid.

Both will rev on neutral, but when the gear selector is on Drive there is no link between the pedal and RPM.

And on Brake it's even the opposite: above a certain speed, you press the accelerator and the RPM decreases to remove engine braking.

They're programmed to rev in situations like that, because people are used to it. Under normal operation, RPM is decided by power needs. If you start accelerating on the freeway, for example, the engine might jump from 1100 RPM to 3000 RPM with just some pedal, while a manual transmission obviously changes very little.

it's possible that the engine rev is just the speakers. a lot of cars are doing fake engine sounds.

The dash has an RPM gauge which moves. Also, the noise is horrendous, not sure why they would have chosen that when they could have used a nicer-sounding tone. This is a tame small car, not something you'd buy to impress your friends.

The whole "pas pedal" becomes faster/slower (one pedal driving) is coming to an end. Its being banned as default in the world's largest EV market (and largest EV export country).

Huh, that's interesting. Apparently China will be banning cars from having one-pedal driving as the default.

Losing muscle memory of pressing the brake pedal. Makes sense, actually.

I'm curious what you mean? I'm fairly confident the post you are responding to was only talking about newer transmissions. Which, I can't imagine those are going away?

The post is talking about most people drive with BEV , which is one pedal driving. My Tesla does one pedal driving my default.

China has banned "one pedal driving" as a default.

I took it to be people that are far more aggressive with the gas pedal than they really need to be. That is, it was more the heavy foot than it was letting off to brake.

Regardless, your point stands. People that have gotten used to not directly using brakes to indicate you are slowing down is a dangerous thing with how reliant we are on the standard indications that you are slowing. All the more so if you need to rapidly lose a ton of speed, where even regenerative brakes often fall back to friction.

> People that have gotten used to not directly using brakes to indicate you are slowing down is a dangerous thing with how reliant we are on the standard indications that you are slowing.

Most, if not all, EVs will light up the brake lights when you're slowing via regen braking as long as the deceleration rate is above a certain threshold. I know my Tesla does.

This addresses the signalling to the people behind you problem. You still should have the foot nearer the brake so that you can fully stop, if you need to do so rapidly.

Emergency brake systems probably help a lot with this problem, of course. Still seems wise to follow some of the older practices that we used to drill into people.

So you just type in the speed you want and hit enter?

> […] but there can also be a significant benefit from allowing the ICE to remain in the RPM "sweet spot" rather than moving around a larger range.

Which is why I'm surprised electric cars with range extenders aren't a bigger thing:

* https://en.wikipedia.org/wiki/Range_extender

Have the powertrain be all-electric, and have a battery pack, but for those with range anxiety have a small generator as an option that would go in the frunk (front truck). A (proverbial) small Honda EU2200i would be less maintenance than a traditional engine.

The EU2200i can sustain 15 amps. That charges most EVs at something like a few miles of range per hour. The biggest one that’s small enough for a frunk is the 3200i, which still only sustains 21.7 amps - plus, that’s from an L5-30R socket, so you’d need an adapter for the EV, and a custom chip to limit charging current below that, since the ones I’ve seen for that socket assume they can pull 24 amps.

Re: maintenance, small engines typically are pretty needy. That one wants an oil change, spark plug gap adjustment, and spark arrestor cleaning every 100 hours of use. The latter two are only usage-based, but the oil is time-based as well (6 months) since it oxidizes, and suffers from fuel dilution. Then there’s the fuel: god help you if you put ethanol gas into a small engine and let it sit for any period of time. It’s often difficult to find E0 fuel, and while there are external fuel tanks for generators that can hold quite a bit, they also tend to vent vapor in the heat (as does any tank, including a car’s), which is unpleasant when it’s in your frunk.

Finally, engines of all kinds really don’t like being left sitting for months on end unless prepared to do so. Generally you want to run them monthly, getting them up to operating temperature, putting a load on them for a bit to fully exercise all components.

I say all this because I have an EU2200i and dearly love it, but am also painfully aware of its limitations and needs. I got it when I lived in Texas because the power outages were getting to be absurd, and my house wasn’t plumbed for natural gas, so a whole-house was out of the question. The 2200i was plenty to power two fridges, a deep freezer, TV, fans, and my server rack. I got really good at quickly running extension cords (which is a whole other discussion on ensuring proper amperage ratings and calculating voltage drop, something most people ignore).

> The EU2200i can sustain 15 amps.

proverbial

I’ve ran mine at nearly that for hours without any issue. Honda generators do what they say they’ll do.

For a Honda 2.2kW to aid with range anxiety, you'd have to split range anxiety into two categories and I think it only addresses the second/lesser of the two.

Assume the car gets 4 miles per kWh delivered and the charging cycle is 90% efficient (measured from generator output). The 2.2kW generator can add 8 miles/hour of generator runtime (2.2 kW * 0.9 * 4 miles/kWh).

For range anxiety of the form "we're driving to a destination pretty far away and I'm not sure we can get there", that's not very helpful. For range anxiety of "I'm driving to a destination that's over half my range and then going to spend a full day [or overnight] there, but I'm not sure there will be working chargers available there", charging 8 mph times 8-10 hours is very helpful.

Worrying about being stuck in the boondocks without a charger is addressed by an 8 mph on-board charger, but I think that's the less common form of range anxiety.

The Chevy Volt range extender was 75kW; the i3's was 26.6kW. 2.2kW is literally an order of magnitude too small to replace those.

Posted something very similar above. It’s worse than 2200 watts: that’s the allowable overload draw, not sustained. After about 5 minutes, it warns you to reduce power to <= 1800 watts.

Also, something I didn’t mention in my post; at full power they’ll suck their tank dry in a little over 3 hours. You’ll get about 20 miles of range (using your assumptions above) from one. Tbf you can also parallel two of them, or buy a slightly larger model (EU3200i), but either way, it’s still not going to be anything other than an emergency backup where you have a lot of time to kill.

BMW tried that with the i3, it wasn't particularly popular. An engine, fuel system and a generator are all relatively complex additions compared to just putting the same cost and vehicle space into more batteries, and the public charging networks are definitely up to the task by now (having been EV-only for almost 5 years now).

I've ridden in one and this was basically a case of "you get the worst of both worlds". The engine was small and running at a constant RPM, leading to an annoying noise in the cabin. The range extension was not particularly huge. Worse, when we did eventually run out of battery on one trip, the range extender was unable to recharge the battery after refueling the car, forcing us to scramble to find an available charging station with the car on the tow truck...

I've been driving one for a while. On the trips I've driven, even on the highway, the engine was able to keep up with the energy draw. I think it's around 60HP. If I'm on a long trip, I'll start the engine once I reach 75% of my battery capacity. That gives a significant buffer for the engine. It's a serial hybrid.

Yes, the Volt was a better balanced version of that. It had a longer EV range and the range extender was larger. It was much less likely to need the range extender and when it did, the larger (1.4l) engine was no more noisy than any gas engine.

>> the range extender was unable to recharge the battery

Could you expand on this? What was the actual problem? For example, did the range extender start and run? Did it put any energy into the battery at all?

We ran out of battery and fuel (I was on the backseat so I don't remember the exact sequence, I just remember the car basically losing power without much warning on the autobahn). The car was towed to a gas station were we proceeded to refill the tank, but the range extender would not start and the car computer was adamant we had to recharge. Which led to a quest to find a public charger in the middle of the night, after 2 failed attempts, we gave up and asked to be towed to our destination instead since it was close enough.

The original BMW i3 had/has a lockout that prevented the range extender from charging the battery until it reached 6% in order to meet California's ZEV BEVx regulation.

facepalm

I don't know what to call this.

"Legislated fragility"

> An engine, fuel system and a generator are all relatively complex additions […]

And yet that's what an ICE car is.

So a range extender (RX) should be no worse than ICE: in fact a little less complex because you don't have a gear train and transmission.

The newer London black cabs do that

> The LEVC TX is powered by a full-electric hybrid drivetrain. It drives in full-electric mode all the time, but is recharged by an 81-horsepower (60 kW; 82 PS) Volvo-sourced 1.5-litre turbocharged three-cylinder petrol engine.

This does not make any sense. It's a cab, it's going to stay 100% of the time in a city or really near, moving around. If it ignites a petrol engine to recharge the battery, what's the point? Surely a cab driver can pause 20 minutes every 4 hours to go to the restroom and fast charge their EV, no?

Diesel REX vans would be a MASSIVE hit if a company would just decide to start making them.

The #1 reason for (european) companies not buying full EV vans is range, they need to drive a LOT during the day.

REX would solve that with minimal emissions. And depending on the battery size, they could drive on full EV in city centres and only allow the REX to charge the battery during longer drives.

The BMW i3 REX is a fantastic car, if you can find one, buy it.

They are the cheapest hybrid out there currently, at least here in the USA. I think the average American prefers a larger vehicle.

I think a Diesel indirect injection REX would be awesome. It could burn vegetable oil, which is more viscous, but indirect injection doesn't need to atomize the fuel as much.

Range anxiety seems to go away after your first week of EV driving.

I'd say more that it evolves rather than goes away. We've had our BEV for over a decade and it's the car we tend to choose to drive for short distance errands. We like it by all means, but when one of us needs to take the hybrid car for a weekend or a local business trip, we still have to plan out to make sure the other can manage whatever we need to do with just the BEV.

As dboreham says in the sibling comment, the range anxiety morphs into charger-availability anxiety. Even if I know a charger physically exists at my destination, if it's 45% or more of the range away, I still need to worry that it will be working, that my access will work, that it won't be occupied or blocked, etc.

In nearly 40 years of driving, I almost never researched gasoline availability (through the Nevada desert and in Central America, I did).

In a little over a decade of BEV driving, I've done a lot of EVSE (charger) researching.

It isn't really "range" anxiety, rather "no charger available" anxiety.

Today, if I run out of petrol|gasoline somewhere, even if I'm in the middle of nowhere and don't have a gas can, I can still recover from that situation within an hour or so (hitch a ride to the next gas station, buy gas can, fill with gas, hitch back to my vehicle). With an EV the density of fueling/charging locations is orders of magnitude lower than for gas, and if I end up discharged I'm looking at finding a flat bed truck, or perhaps a mobile high power generator.

Disclosure: I own both kinds of vehicles.

Eh, I'd say it goes away after your first road trip, unless you're going somewhere remote.

I've had my BEV for about 5 1/2 years. My first road trip (Portland -> Santa Clara, ~560 miles each way), I planned it out ahead of time with ABRP. These days, I'll just let the nav figure it out.

First time I did an EV road trip, I just plugged it straight into the car screen and followed directions. I didn't have anyone with me, and was willing to accept some degree of "adventure". I did about 800 miles in a day, and had zero real issues.

I have been totally unconcerned about it since.

One 120V 2.2kW generator isn’t going do much at all. It’s really actually 1.8kW which is 15A at 120V.

You’d need to tow around a 7.2kW 240V for 30A at 240V (more likely a 14.4kW generator for 240V 60A).

Using the small Honda inverter generator (which is amazing for plenty of stuff!) is akin to covering your car in solar panels to get range extension, the math just doesn’t work out.

Maybe because people don't want to have oil changes, emission checks, exhaust gas etc. on their EV. If they really need a long range, they will probably just buy a combustion engine car.

Perhaps, but other than the upcoming Scout, I’m not even sure it’s an option for EVs, in the US.

BMW i3 has/had a REX version and when I researched it people seemed to agree it’s the least reliable part about owning it. But that might be it!

Afaik that’s pure series hybrid and that’s almost non-existent in cars (outside of range extenders, not that there are that many of those).

There are a handful but most hybrids are either parallel or series-parallel. I assume because the power range is so low that the conversion losses are way too noticeable compared to a mechanical drivetrain.

No, the entire point of a series-parallel hybrid is that it can offer the advantage of a series hybrid.

The Toyota Prius powerchain has two motor generators, and can take part of the ICE power from one and transfer it electrically to the other, remapping the engine RPM into more efficient power bands at the same time. It has a mode that can do this even when no power is being used from the battery.

It’s kind of a best of both worlds. They can avoid the extra weight of a full series hybrid, because they don’t need a motor generator pair that handles the full engine power.

Actually, power bands remapping is essential for the Prius to operate.

There is no clutch, there is no neutral gear, there is no torque converter. The ICE is always connected directly to the wheels with a fixed gear ratio on a planetary gear set. (Which improves transmission efficiency over a automatic/CVT gearbox, and actually reduces maintenance costs)

One of the motor-generators is on the 3rd input of the planetary gear. For the ICE to idle (during warm up, or when you have the heater on), the motor-generator much be spinning backwards at the exact same speed so that the wheels stay stationary.

Power band remapping can also be used for reversing when the battery is empty.

Current Honda hybrids are like that. The only time the Internal Combustion Engine (ICE) is directly connected to the drive train is when the speed gets to above around 60MPH. The rest of the time the ICE is used to power a generator which then sends power to the electric motor and/or the battery pack.

https://www.youtube.com/watch?v=QLUIExAnNcE has more info.

That's something I wish there had been more focus on, instead of focusing on massive heavy batteries, develop the hybrids further.

Not sure about the US, but the Japanese didn't stop focusing on hybrid development. More than half of all sales in Japan are hybrids, whereas electric is only a few percent [1].

Honda even recently announced that they're scaling back on electric to focus on hybrids:

https://www.reuters.com/business/autos-transportation/japans...

[1] https://www.bloomberg.com/news/articles/2023-12-19/hybrid-ca...

Yes but Honda seems to be doing this because they can’t make batteries. BYD can, ever cheaper, and they’re expanding their plug-in offerings much faster than Honda is scaling them back. I’m worried for Japanese car makers.

Yep. Hybrids are a dead end, they’ll be obsolete in a few short years

But series-parallel has the very same advantage - can keep the RPM in sweet spot.

This is how diesel-electric locomotives work too.

They also use the electric motor(s) for braking, but instead of going into a battery it goes into a bank of resistors.

I think you meant capacitors. Resistors would just dissipate the energy as heat.

edit: Thanks for the correction. They do indeed use resistors and just dump the energy as heat. Unfortunate.

Hopefully this will change as supercaps continue to improve. Maxwell tech's modules are already used in light rail, and looks like some work towards smaller locomotives in Switzerland here:

https://www.osti.gov/etdeweb/servlets/purl/20823697

Capacitors have pitiful energy storage capacity. Resistors is correct, unfortunately.

Nope, resistors. The energy is dumped as heat.

Dynamic brake

To add to the other comments: https://en.wikipedia.org/wiki/Dynamic_braking

Most hybrids on the road are parallel and have a mechanical connection to wheels and vary rpm as needed, although the CVT implementations may hold rpm due to gear ratios like any CVT hybrid or not.

A direct mechanical connection is more efficient at highway cruise speeds than a mechanical->electric->mechanical conversion.

The main win a gasoline hybrid has is in running the Atkinson cycle gaining efficiency while losing torque which the electric motor makes up. This brings the gasoline engine up into diesel efficiency territory.

This is also why you don't really diesel hybrids, the engine is already very efficient but it is more expensive and heavier and hybrid adds more expense and weight.

Diesel engines with all their turbochargers, EGR, SCR, DPF etc equipment, work pretty well as part of a hybrid system. All that stuff works much better in steady-state operation. Diesel hybrid buses and trucks are much smoother and cleaner than non-hybrid.

There do exist serial hybrids where the engine produces electricity while maintaining the ideal RPM, and then is connected to a battery+electric motors.

However in practice the vast majority of hybrids do not use this approach and have motors that vary RPM with road speed (depending of gearing of course).

The common case of maintaining ideal RPM is the CVT, which most folks dislike, so much so that some models have a switch to pick how many fake gears you have to break up the boring drone of a constant RPM engine.

BTW, the chevy bolt was advertised as a serial hybrid, right up to the day it shipped.

I believe the most common serial hybrid today is an EV with a range extender.

I heard about that long ago but couldn't find more, so IIUC chemically it's easier and more efficient to have a "one mode" combustion engine and let the electric engine deal with the variations, to the point that the reaction produces near no toxic byproducts, is that right ? I was wondering if there was research to keep improving that part. Even though it would help sustain the fossil fuel industry..

Nissan hat the e-POWER system where a petrol engine is just used to recharge the battery of your electric car and nothing else. In theory they could run that petrol engine at the sweet spot where it produces the least amount of carbon emissions.

i believe there is also a chinese company which is making such a car, their cars have nearly 1000 miles range.

Diesel-electric engines in trains and tanks worked like that during WW2.

AFAIK this is about engine efficiency. ICEs have highest momentum and efficiency sweet spot somewhere in the middle of available revs, which depends on the engine construction and was being altered by different mechanisms (like turbocharging and variable valve timing) but since the electric engine (I'm speaking of Toyota solution) is able to keep the ICE in the sweet spot with its eCVT, the engine can be simplified and even work on different combustion cycle (Atkinson's cycle)

> ICEs have highest momentum and efficiency sweet spot somewhere in the middle of available revs

Close: they have the highest efficiency at about 90% of maximum torque for most of the RPM range. So if you want double the power, you want to be able to double the RPM; and if you want half the power, you want to be able to drop the RPMs in half. To pull this off, you either need a very quick shifting gearbox or some sort of CVT.

This is also why automatic transmissions, despite being ~80% efficient versus ~95% manual transmissions, are not much worse on mileage. Because they can quickly switch between low RPM and higher RPM (first by torque converter lockup, second by switching gears).

> a significant benefit from allowing the ICE to remain in the RPM "sweet spot" rather than moving around a larger range.

I remember buying plans from the Whole Earth News for such a car back around 1980. That was the selling point - keep the ICE running at an optimal point. I've not seen those same plans reproduced online.

Aha! https://store.motherearthnews.com/products/hybrid-car-bluepr...

In order to do this with a gas engine, it can be done but you need to completely mechanically decouple the gas engine from the drivetrain. The gas engine needs to do one thing and one thing only which is charge the battery. The gas engine has maximum efficiency at about 80% throttle.

The efficiency of the entire system is more important than the efficiency of the engine itself. Charging the battery and then discharging it also incurs losses. Many series hybrids will prioritize generating electricity when some of it is also required to directly drive the motor. They usually don't sit around at low-load situations just generating electricity, unless SOC is low.

> The gas engine has maximum efficiency at about 80% throttle.

ICE efficiency varies in multiple dimensions based on load and RPM, and in a series hybrid, you have some ability to dynamically influence these... throttle would be one of those inputs.

That's the case only with CVT transmission

Are there still a lot of hybrids without CVTs?

Hyundai/Kia use a traditional 6-speed auto in their hybrids. I drive one, the engine stays at a few RPM stepping points during most driving (it likes ~1600RPM, ~2200RPM, and ~3600RPM). I had a Prius previously, and I like this different setup because it reduces "engine droning noise", which was terrible on the Prius.

Though H/K have recently introduced a new hybrid system with a CVT, so maybe 2026 or 27 model years will be different.

Since I'm only making one comment, I also want to say hybrid cars are better than ICE because there are fewer belt-driven accessories. Aircon in particular on an electric motor is a big improvement. Without the idling engine producing heat, hybrids are much nicer in hot stop-and-go conditions!

Also my Prius made it its whole life (200k miles and ~20 years) without ever changing the brake pads... amazing!

I'd say that the market is very fragmented.

Toyota and Lexus, obviously, use eCVT in their cars.

Honda is also in eCVT camp for most of their models but for example new CR-V has weird setup. It acts as an BEV until ~80-100kmh and then shifts completely to ICE with a single gear. While in EV mode the engine is constantly charging batteries.

Then you have KIA and Hyundai with their dual clutch setup in all HEV and PHEV range.

Lots. BMW, Audi, Mercedes, Porsche, Volkswagen, Volvo for example.

I find it a pity that Lexus uses CVTs as I would probably sell my BMW 330e and get a Lexus.

Yes, but only to some degree.

Quote from the actual report:

> As the level of electrification of a vehicle rises, the dependence on regenerative braking also increases, thus lowering PM emissions from brake wear. Based on recent evidence [30], regenerative braking can reduce, in the worst- case scenario (i.e. highest usage of mechanical brakes or equivalently lowest usage of regenerative braking), brake wear emissions by 10-48% for hybrid electric vehicles (HEVs), 66% for plug-in hybrid electric vehicles (PHEVs), and 83% for battery electric vehicles (BEVs

This makes sense since vehicles with bigger batteries can absorb more energy with regenerative braking.

I remember decades ago where they figured out the horsepower of a high-end porsche to go 0-100-0, and if the acceleration horsepower expended was 500hp, the deceleration horsepower absorbed by the brakes was probably 1000 hp.

I wouldn't be surprised if hybrids could only absorb 10 hp, while bigger cars could absorb 50.

One thought - if any of these manufacturers provided "braking resistors" like diesel-hybrid locomotives use, regenerative energy could be electrically turned into heat, instead of mechanically by wearing the brakes.

using resistors would be "green".

I came across a really interesting video yesterday (https://www.youtube.com/watch?v=Aubi3cK8Ym0) that touches on brake-dust pollution. It also explains how regenerative (kinetic-energy) charging can cut down on heat pollution, something I hadn’t realized before. That’s actually a big deal for underground metro systems; for instance, the London Tube keeps getting hotter every year.

Yes indeed the London underground does use regenerative braking on many of their lines. The cool thing about a direct rail power system is that the voltage generated from trains that are braking can be fed back into the power rail to instantaneously power other trains on the same line that are accelerating. No need to carry the extra weight of a battery or flywheel. And like you say, it helps keep the tunnels cooler.

It has to be the same segment, which is a bit of a pain to manage. The amount of power being fed in is getting close to megawatts.

The rear brake rotors on my Yaris hybrid are basically always rusty because they get used so little. After some time you just know when to start braking so you only use regen instead of the brakes.

I confirm and that’s an unpleasant surprise. Already had to replace the rear rotors and pads on my Highlander… because of rust. They should add some “brake cleaning” mode to temporarily disable regenerative braking.

There’s been a few suggestions that drum brakes should make a come back, for EVs.

They’re enclosed so they don’t get dirty, the inner face of drum will rust less than discs, fade is not an issue thanks to regen braking, and before they get too hot and fade drums will brake harder than disks (thanks to a higher pad surface area). And they’re enclosed so they also keep the brake dust inside the drum, making it easier to dispose of safely.

Drums are heavier tho.

Drum brakes are cheaper, too. The VW ID4 has rear drum brakes for all of these reasons and it seems to work out very well.

Many of the cars with regenerative braking already do apply the brakes once in a while to prevent them from rusting.

Also forget about that bit:

> They should add some “brake cleaning” mode to temporarily disable regenerative braking.

Some manufacturers do that (iirc tesla calls it burninshing, others will switch regen off completely if you switch to neutral or something).

I've read that Audi and Porsche will use regular brakes once or twice at the start of every drive instead of regen, I assume using electronic control to imitate the current state of regen braking.

> They should add some “brake cleaning” mode

Also known as breaking. You could just do that once in a while.

If you don't break hard enough, it might still be the recuperation doing its work.

Car producers can and do resolve this, e.g. iirc Audis don't use recuperation for the first breaking of the day. That way you don't have to remember to use the no-recuperation/break cleaning mode or break unnecessarily hard every now and then.

The manual recommends putting the car in neutral and then braking every once in a while to keep the brakes in good working order. Putting the car in neutral disables the recuperation and makes sure you really use the friction brakes.

(When I say "the manual", I mean both the manual of my previous car which was a hybrid Toyota Auris, and my current car which is a fully electric Volvo XC40.)

*braking

* https://www.dictionary.com/e/brake-vs-break/

The two words are:

* https://en.wikipedia.org/wiki/Homophone

Modern EVs tend to do blended braking (at least by default) in which case pressing the brake pedal gently will likely just do more regen braking. It’s only when you request more than regen braking can provide that physical brakes engage.

Yup, my Golf GTE is mostly used to fetch groceries, but every now and again I'll blast down a faster road and brake harder than just regen to keep the brakes themselves in good condition. It's almost second-nature at this point.

Sure, gonna slam on brakes while in front of you.

It's 2025 and hybrids have enough software to automate some non-hybrid braking action.

It does. My Volvo XC60 T8 PHEV is a 400bhp 2.2 tonne SUV and after over 5 years of ownership the pads are about 20% worn. And I don't drive like a granny either. The car just does most of its braking with the EV motor.

Same here, XC40P8 and the pads are 10% used after 2.5 years.

But I understand the factory tires are a bit stickier to create a quieter ride which may be throwing more rubber dust into the air. High torque launches don't help either. ;-)

UK stats are different: https://www.zap-map.com/ev-stats/ev-market , possibly due to the shorter max travel distances.

> As of the end of June 2025, there were 2,450,462 plug-in cars, with over 1,585,000 battery-electric cars and nearly 865,000 PHEVs, registered in the UK.

> There are more fully electric cars than there are plug-in hybrids on UK roads and the gap has been widening. In 2021, fully electric cars accounted for 60% of all plug-in cars but with the increase in options, range and popularity of fully electric cars, and by May 2025 this has increased to 65%.

(That stat does exclude non-pluggable-hybrids, but those are kind of pointless stalling of the transition off petrol)

Your source doesn't consider non-plug-in hybrids also known as HEVs because zapmap are a company that sell charging services. The number of HEVs in the UK is about twice the the number of PHEVs so the total number of hybrids is still higher than the total number of BEVs. In 2024, 6% of vehicles on the road were hybrid compared with 3.7% fully electric.

https://www.smmt.co.uk/more-than-a-million-evs-on-uk-roads-a...

I wonder which vehicles that is - is that predominantly the non-pluggable Prius?

There is a wide variety, MHEV is quite popular here due to lack of home charging, as many people live in terraces, etc

We have a selection of smaller popular hatchbacks with MHEV available (ie, the Hyundai i20) that I believe were not released in some markets

The leasing culture for "luxury" cars is quite prevalent here too, and many new cars from popular brands such as Land Rover are at minimum MHEV from new nowadays, in order to get fleet emissions down

To some extent, but not really. Effectiveness of regenerative braking depends on having an extremely large battery that can sink enough current to stop the car. An EV can do that, hybrids at best help the brakes out some. You just can't charge the battery fast enough doing anything but a very slow rolling stop. My model Y can effect a very reasonable stop in traffic without touching the brake pedal except to hold the car at the end.

> Effectiveness of regenerative braking depends on having an extremely large battery that can sink enough current to stop the car. An EV can do that, hybrids at best help the brakes out some. You just can't charge the battery fast enough doing anything but a very slow rolling stop.

This seems a bit exaggerated. Staying regenerative-only does require sticking to about half or so of how fast I could stop, but so far that seems to work fine unless a light turns right in front of me or traffic acts up. Usually it says it gets high 90's or 100%, and it didn't go below 50% even when a stoplight did turn at exactly the wrong time. (2022 Ford Escape non-plug-in hybrid, recently bought used.)

It's just that Tesla didn't spend skill points on brake blending tech unlockable. Some people confuse it as being a piece of technology of its own.

Every other EVs and HVs assign first half of brake pedal for regen and bottom half for mechanical brakes. Tesla uses bottom half of gas pedal for the same, which eliminates the need to accurately determine the appropriate pedal force that corresponds to intended braking force to be added up with regen to match intended deceleration. Mapping regen to gas is `set_motor_torque(1.25 * gas_pedal - 25);` and that's much simpler.

This is something that's always baffled me about Teslas. I have a Prius, and regenerative breaking being tied to the break pedal is easy and intuitive. It also means I can easily lift my foot of the gas pedal to coast. IDK it just seems like a much better design to have one "stop" pedal and one "go" pedal, vs one "stop" pedal and one "go/stop" pedal.

Counterargument is that it's even easier to have only one pedal you use to accelerate and decelerate. Having owned a Prius and a Y, the Tesla is actually smoother to control, by a very significant margin. It's actually a superior way to drive, though it is surprising the first time you see it.

They didn't spend skill points because back when they did it they wanted to lean hard into the "oooh, fancy futuristic EV, look at this cool new driving experience" brand image. Same reason performance cars get loud exhausts even thought they could have quit ones with no decrease in performance.

100% of possible system capacity to accept regenerative charge on a smaller battery system will be a smaller absolute number than 100% of possible on a larger battery. If you assume everything else is constant, motor, inverter, battery C-rating etc.

I'm not sure what you're arguing here.

Bigger battery is more capacity sure. But their point was that even without a big battery they have enough capacity to get close to maximum effectiveness, contrary to ajross saying that a hybrid's capacity is "not really" effective and "at best" helps "some".

just mistaken about maximum effectiveness

braking system = circa 1G of deceleration possible (depending on tyres, coeff of friction, temperature, ... etc etc)

So max effectiveness is unreachable for any regen system on a consumer car hybrid or ev, by a factor of around 6x i believe?

With recognition of the mistaken framing (near max effectiveness) we're back to the larger ev pack has a greater ability to sink current, a larger ability to slow the vehicle than does a smaller battery (obvious considerations about inverter capability, wire gauge etc etc aside)

I think you might be using a very different definition of "effectiveness" than they are.

Their definition of effectiveness is the percentage of braking force that turns back into electricity and goes into the battery. If your regen system can only do .15G, but 90% of your braking is under .15G, then you'll have about 94% effectiveness by that definition. 94% is not max but it's near max.

It's not about what happens during peak braking, it's about what happens over entire drives.

And when they say "half or so of how fast I could stop" they're underestimating, that's a comparison to a normal but aggressive stop, not pushing the pedal into the ground.

The manual says it's energy recovered (ie, not something relative to system capacity), and this seems consistent with the other indicator that shows instantaneous braking power with a distinction between what the regenerative system is doing vs what (if anything) the traditional brakes are doing.

which car? i think the number you're referring to is relative to electrical system capacity.

It's NOT relevant to overall (tyre, brake system & engine braking & regen braking) braking system performance since that's a dynamic value variable over many factors constantly.

I won't speak to your '22 Escape, but I've driven countless hybrids going back to a '04 Prius and none of them were brake-free in general use. EVs really are.

That's because the regenerative braking is applied on the brake pedal, not by lifting up the accelerator. My '14 Prius has a dashboard option to show how much of the regenerative breaking capacity is being used, and it's very easy to stay well below that limit by just gradually slowing down. The friction brakes are only really used when you suddenly stop, which is something you want to avoid anyway.

And when regenerative breaking is not enough, a series hybrid can still apply compression breaking, before resorting to brakes.

> You just can't charge the battery fast enough doing anything but a very slow rolling stop.

And it's not a problem when you get used to regenerative-only braking distances, which are surprisingly long at highway speeds.

It only becomes a problem when idiots thinking "the shorter the distance between first and last car, the smaller the traffic" start cutting you off when you leave enough distance for regenerative braking.

We finally gave up our Prius after 12 years, and we never changed the brakes once. The brakes were just peeking into the yellow on its last service upgrade. I was really impressed with how well the "normal" hybrid could take advantage of regenerative breaking, honestly.

I first changed the brakes on my Mitsubishi Space Star (combustion) after 13 years. It is a small car, less than 1000kg, so there is little for the brakes to do. If we produced more percentage of small cars, many environmental risks would be reduced. And btw.: The tires are now 19 years old and still good (less weight, less abrasion!).

That's not OK by any means, you don't have mandatory periodical technical inspections? This would fail immediately in any half-decent country. An example - wife's older Seat has 6 years old winter tires which were given for free when buying it second hand a year ago. Technician just told us even those are beyond acceptable here in Switzerland and we need to change them before next inspection.

Your very old tires makes you a serious threat on the road while completely oblivious about this fact... not cool, please change them if you drive on public roads, if not for you just for the sake of others.

We are in Germany, which has the highest inspection standards. The tires have passed every inspection. They look like new, but I will still replace them soon, just in case. I am writing this because most people cannot imagine that a 900 kg car puts very little pressure on tires, so they are hardly used.

Rubber degrades with UV exposure, even if the tread depth is ok. Be careful, esp at higher speeds.

Beware of dry rot. Rubber that old is likely not in as good shape as it might appear, and could fail catastrophically in the right conditions.

Seriously, you should not use tires older than 10 years. They degrade over time.

Time based degradation is mostly a factor of exposure to the sun and the weather.

I just trashed some 15yo Firestones last month, after wearing them completely bald of course.

> My model Y can effect a very reasonable stop in traffic without touching the brake pedal except to hold the car at the end.

My manual car could do this 20 years ago. My fully ICE motorcycle can do it today.

I know engine braking is cool but it’s not some amazing new thing only EVs can do. Altho granted it only produces heat and noise in petrol vehicles. But it also makes your heart sing so that’s nice

The difference is neither of those generates gasoline on an ICE vehicle.

Yup. For example on a round trip today in me EV (2025 Hyundai Kona) on the out here are the stats:

     2 kWh for the drivetrain
   809  Wh regenerated

On the way home:

     2 kWh for the drivetrain
   547  Wh regenerated

For the round trip that's 33% less energy use than if the car did not have regenerative braking.

I'm mostly happy about that but there is one thing that annoys me. 33% is close to how much a kilometer is shorter than a mile (38%).

Why the fuck would I care that these two numbers are that close? It is because of a mystery in the Hyundai app. When you look up the trip details for an EV trip it gives you mileage, duration, and energy use (drivetrain, climate, accessories) and regeneration.

The mileage is substantially less than what the car shows. For example for the aforementioned trip home that trip odometer shows 8.0 miles but the Hyundai app shows 5 miles. The car odometer has the correct distance.

There are two theories to explain this.

1. The app is showing how many miles worth of energy you used rather than your actual trip mileage. All the other data it shows (except for the duration) is energy related. For my 8.0 mile trip I got 3 miles worth of the energy the drivetrain used back via regeneration, so I only actually paid for 5 miles worth of electricity.

Based on the Wh given it should actually be 5.4 miles, but the app only displays integer mileage so 5 it is.

2. It's a botched unit conversion. E.g., the car uploads the data in miles but the expects the data to be in km, so it is doing a conversion. That would turn the 8.0 into 5.0, which would be 5 in the app and so matches what theory #1 predicts.

I've checked several of my trips and they have always happened to have the right amount of regeneration so that the two theories match due to the app only showing an integer mileage.

I did a test today to try to tell them apart. I changed the car's settings to km and took a trip. The idea was if the car had been uploading in miles that would hopefully change it to upload in km, matching the app's expectation, and so the miles shown in the app would match the actual miles of the trip if theory #2 was correct, and show the regeneration corrected miles if theory #1 was correct.

The result was that the app still showed miles consistent with theory #1. So mystery solved, right?

Maybe not. When the car was set to miles everything showed in miles. Speedometer, odometers, efficiency (mi/kWh), speed limits it read from traffic signs, and speed limits it gets from the map data when using navigation on highways.

I expected than when I switched it to km all of those would be in km, and I would not see miles anywhere. Also, I expected that when it saw a speed limit sign that said say 60 it would interpret that as 60 km/hr.

What actually happened is that miles mostly did go away, except on the speedometer it added a smaller mi/hr display under the km/hr display. For the traffic signs it still knew they were in mi/hr and it converted them, so when I got on the freeway as soon as I passed the sign that said 60 the speed limit sign shown on the instrument cluster said 97, and the red dot on the speedometer showing the current limit was placed in the right place.

That suggests that the car knows it is in a country that uses miles, and doesn't just go by whatever the units setting in the setup screen is set to. It could be that in miles countries the car also uploads in miles all the time, and so switching the units setting to km would not change the results if theory #2 was true.

Now my plan is to find a big parking lot that is mostly empty overnight, such at a Walmart or Home Depot or a mall, go there and turn the car off and then back on which starts a new trip, set regeneration to 0 which turns off automatic regeneration on the accelerator so the car only regenerates when you use the brake pedal, and then drive around the parking lot for about 10 miles without using the brakes, then coast to a stop and turn the car off the end the trip.

Then I'll turn it back on, drive home, and check the trip details in the app. If theory #1 is right then the miles in the app should match the odometer miles. If theory #2 is correct the app miles should still be 38% shorter than the odometer miles.

And how often did you engine break with that ICE car when driving around the city? Because I did it only when driving down extreme slopes. It also cannot do a full stop.

With an EV I don't touch breaks unless in situations I fail to/couldn't predict (maybe up to 10% of all speed reductions and even less stops).

> And how often did you engine break with that ICE car when driving around the city?

Oh all the time. I used to drive like a typical youth. I've been in USA for 10 years now and still hate driving automatics because they shift into too high a gear and then you have to constantly use the brakes. It's annoying.

Most autos have an override to shift manually and engine brake more, hardly ever see people use them except if they tow frequently though.

A lot of CVTs have virtual gears for that even, although others like the prius only have B mode.

I have an ICE car and motorcycle, and an EV. The EV slows down much more quickly when slowing down, to the point where it's a good replacement for the brake, as opposed to the ICE vehicles, where you need to use the brake a lot more. It's not comparable.

> The EV slows down much more quickly when slowing down, to the point where it's a good replacement for the brake

Are you comparing to an automatic ICE or a manual?

In my experience of driving EVs their engine braking is sub-par to what I'm used to at least from my motorcycle. Bikes have silly high compression compared to their weight. You def have to be careful about chopping the throttle.

An automatic, with a manual you can shift down to whatever you want, so there's no standard there, really.

Agree the engine braking on automatics sucks. If you re-read my original post, it specifically talked about manuals :)

And I mean if drifters can use shift lock to literally skid their wheels, then clearly engine braking is effective.

With manuals I don't tend to downshift to brake. I certainly could, but it's so jarring (mostly the sudden rev) that I tend to just use the brakes, and what matters is what people do, not what they could do.

I am talking about what I do do :)

Also I learned in driving school in Europe (and during the motorcycle course in USA) to downshift while braking so your engine helps the brakes and you’re always in the right gear. There shouldn’t be any sudden revs if you’re gentle with the clutch.

Then again as a young idiot I also learned how to heel-and-toe on public roads so I could rev match more effectively while braking into corners. Maybe I’m just a weird driver with unusual habits. It’s ok.

Can’t really compare the engine braking of a Model Y and a ICE vehicle to be honest.

I also like the noise, but it is noise pollution that is very annoying to everyone else.

In normal driving hybrid regen is more than enough to do the job. Just look at the front wheels of any Prius. There are reasons all the Uber drivers choose the Prius.

If your Model Y is like my Model 3, then it seamlessly switches to friction breaking below 20 kph. That said, I'm at 110,000 km and the brakes look like new.

You can just waste energy on eddy currents, and then use the car's cooling system to conduct away the heat. After all, dynamic brakes on locomotives just dissipate the generated electricity using resistors.

Hybrid makers just don't really care about that.

I test drove an EV and the regenerative braking was difficult to get used to. You have to constantly ride the gas pedal. I would buy an EV if it weren't for this feature.

We have owned 4 EVs and each allow you to configure the regen braking strength. You'll need another reason to not buy one.

Tesla is a quite common EV brand. They do not allow configuring regen braking, except for the behaviour at stand-still.

(They also don't do blending between friction brakes and regen, so the cars behaviour when letting of the accelerator is highly inconsistent depending on temperature and charge level).

One of the reasons I long for the lease on my Model Y to end so I can replace it with a less stupid vehicle.

I agree with the general sentiment, but this isn't relevant in the context of making a purchasing decision. Simply buy another brand.

I have learned my lesson on regen. Lots of people online (and offline, for that matter) told me that you'll get used to the Tesla behaviour in no time and not to worry about it feeling weird during the test drive.

Many thousands kilometers later I hate it almost as much as at the start, so lack of regen configuration will be a dealbreaker next time I pick a new car.

Hmm, what do you hate about it? I have a BYD and I always leave it at "strong", as otherwise it's too little braking (same as an ICE).

There are two aspect I don't like:

1. It is inconsistent, especially during winter and when fully charged.

2. Crossings with shrubbery/objects that hides approaching pedestrians/cars/bikes and it is rare that there is anyone actually crossing. I encounter these several times per day.

My preferred way of approaching #2 is to reduce speed well ahead, start gliding and put my foot on the break pedal to be ready for a complete halt in the rare case (once in a 500 maybe) that I need to give way to someone. In the Tesla I must reduce speed to almost standstill and creep slooooowly, since it would take half a second to move the right foot to the break.

I understand it sounds like an extreme corner case, but for me it is all the time every day. Central Scandinavia.

Hmm, I don't really understand what you mean. If I want to reduce speed far ahead, I just ease up on the throttle pedal a little, and the car slows down a little. If I ease up a lot, it slows down a lot. I'm not sure what you mean...

I want to glide at roughly constant speed for some distance. Some mild breaking is fine. I cant glide if I let off the accelerator, then I come to a fairly firm stop.

I want my right foot on the break pedal, ready to brake hard and fast in the rare case that something comes across the road.

I don't want to reduce speed any further than is necessary to have a safe breaking distance at fully ready state.

With any other car (that I have driven) than the Tesla, I can approach a situation like this at between 20kmh and 40kmh, depending on the specifics. In the Tesla I need to go at between 5 and 10kmh.

Ah OK, I see what you mean. Yeah, on my car, that's a setting I can toggle.

regenerative braking can be uncomfortable for passengers as the car is constantly alternating between accelerating (or constant speed) and braking. It isn't even light braking, it is significant braking.

I generally turn off the auto regen braking because i find it uncomfortable.

Importantly, regenerative braking is a danger on icy roads. I disable it entirely in the winter in eastern Canada because it often causes the tires to lose grip.

I agree about the icy roads, but for the braking, that's easily remedied by just not completely releasing the accelerator. I just modulate how much I want to brake with the accelerator pedal.

Is that not what "Chill Mode" is? I've activated that on my car to relieve some of the jerkiness and it seems to have worked well

To be constructive, took me a little over a week to get used to. Also i test drove four, and absolutely hated 2 of them. One felt very similar to my ICE car (VW ID4). Eventually settled on ioniq and after a week, it quickly became my favorite driving car ever (which coming from sporty manual transmissions, is not at all what i expected or why i bought it).

All to say, check out a few to be sure, im still shocked how much i love driving this thing (and how criminally fast it is, totally absurd).

I don't think this comment should be down-voted since it is indeed a real point of difference and it is worth discussing.

The key takeaway is that there are differences to driving an EV to driving an ICE vehicle. Equally those differences are in fact easy to adjust to given a bit of practice.

Of course cars have always had different control options. Automatic and Manual gearboxes spring to mind. When I first learned some cars had a gear selector as an arm on the steering column, and so on.

EVs like a somewhat gentler foot, because the torque is instant, so a heavy foot is likely to be a more uncomfortable ride.

So yes, different cars, different styles. But of course we adjust very quickly, and its not really difficult to drive anything- it just takes a bit of practice.

Except it's not a real point of difference. Just because some cars are programmed to act that way doesn't mean we should treat it like a universal constant of EVs. EVs can be programmed to only engage regenerative braking when the brake pedal is pressed, no riding the gas pedal needed.

Many electric cars are also overpowered. For those with a more reasonable ~100kw, gentleness hardly matters.

> you have to constantly ride the gas pedal.

Are you not? Do you drive by blipping the gas every few seconds?

I've had Uber drivers do this and it is annoying bordering on nauseating as a passenger. It is probably pretty bad for mileage and transmission wear as well (constantly taking up and releasing the backlash in the gears).

I’ve got regenerative breaking on my EV without one pedal driving, it acts just like my other car does.

You can toggle off regen braking on most EVs

Firstly, most EVs that have strong regenerative braking ("one-pedal") setups allow you to adjust the strength or turn it off. Tesla, as usual, is the outlier in this respect.

Secondly, I rented an EV for a week and by the end of it actually preferred the strong regen setting. It was convenient in stop-start traffic, and on a twisty road, you could use it to tighten the nose as you entered the corner.

As another data point, I've owned PHEVs and EVs for gosh 6 years now and I still prefer the "weak" regen with the Chevy paddle brake to modulate. Sometimes when I have a clear path, e.g. a down hill on a highway, I just throw it in neutral for a pure coast and shift back into drive when I need to.

Some EVs allow different levels of regenerative braking to be selected. The Hyundai/Kia E-GMP-based cars have level 0-3 plus a 1-pedal mode, and also an "auto" mode that slows down more based on radar proximity to the car ahead.

> test drove

> was difficult to get used to

To ask the obvious, how used to something are you going to get on a test drive? It takes time.

Take a look at more EVs. There are many that aren't as opinionated about how you should drive as the one you drove (a Tesla, by any chance?).

For example here is how it works in Hyundai EVs (and I'd guess Kia too). It is easy to set them so that they drive very similar to an ICE. I believe several others also work similarly. There are only a few that try to really push you to one pedal driving.

1. When use explicitly use the brake pedal that car uses regenerative braking unless you are trying to stop faster than regeneration can handle in which case it will also use the friction brakes.

There may be a setting somewhere in the settings menus where you can adjust how strong the braking is, but I don't remember because the way the car comes from the factory the brake peddle feels a lot like an ICE car's brake peddle.

2. There is a regeneration level setting that controls what happens when you ease up on the accelerator or remove your foot from it. This setting has 6 possible settings: Level 0, 1, 2, 3, i-Pedal, and Auto.

There are two paddles on the steering wheel that let you move through these settings quickly and easily, and you can do this while driving so you are free to pick whatever setting fits the conditions and your mood the best. Here's what they do.

• In level 0 there is no braking associated with the accelerator. Take your foot off and the car coasts is if it was in neutral.

• Level 1 provides a small amount of automatic braking when you let up on the accelerator. In ICE terms it is similar to the engine braking you would get on level ground going fast enough to be in 3rd gear in a 3 speed automatic. You slow down faster than coasting, but not so fast that if you were on the freeway and your felt the need to shake your right leg around a little it would slow enough to be a problem.

• Levels 2 and 3 step up the amount of automatic braking. 3 is enough that in city driving most of the time you can be quite leisurely when it comes to moving your foot from the accelerator to the brake at most stop signs, but it will not bring your car to a complete stop. It will get quite slow and then creep at that speed.

• i-Pedal is one pedal driving mode and corresponds to what that EV you test drove was doing. In this the braking is similar to level 3 as far as aggressiveness goes, but it will take you all the way to a stop most of the time. Once you get used to it you should be able to do most city driving and most highway driving without touching the brake pedal. About the only times you would need the brake pedal (outside of emergencies) is if a light changes on you when you are too close to the intersection.

• Auto mode automatically switches between 0, 1, 2, and 3 based on the distance to the vehicle in front (using the same system that adaptive cruise control uses) and the slope of the road. If you are on the freeway for example with a good distance between cars it will be in 0 or 1. In the city where you are close to the next car it might be in 2 or 3.

• If you press and hold the "increase regen level" paddle for at least 0.5 seconds it will switch from whatever your current setting is to i-Pedal and stay in i-Pedal as long as you continue to hold the paddle. Release the paddle and it switches back to whatever your previous setting was.

This system gives you plenty of flexibility and you should be able to easily find a setting you like. Some people really like one pedal driving and so they can just put it in i-Pedal and leave it there (with a slight annoyance...when you turn the car off in i-Pedal it comes back on in level 3, so you will have to hit the regen up paddle once).

Some people set it to one of the numbered levels and leave it there (again with slight annoyance at startup where it comes on at 1 so they need a paddle flick or two).

Some people use the paddles instead of the brake pedal, mixing levels to get the kind of deceleration curve they want.

I normally drive in level 0, with an occasional day or two in i-Pedal just for a change of pace, but if I'm coming up on a series of roundabouts I might switch it to i-Pedal. That's great for say a 35 mph road with 10-15 mph roundabouts every couple of blocks. (If it is just one roundabout I'd probably use the "hold regen up paddle for 0.5 seconds" option to just turn on i-Pedal for that intersection.

On both my Volvo PHEVs I often look at the brake discs and find them rusty from the amount of regen braking. it almost completely eliminates conventional braking unless it's for collision avoidance.

My EV turns regenerative braking off for the first use of brakes after beginning a journey, to avoid the rusting disc syndrome.

What car brand is it? I've read that Audi and Porsche do that.

Also is it only pedal braking? Or does it "fake" things out if you use one-pedal driving?

Brake rotors will noticeably rust overnight if left in wet conditions.

So your primary and emergency brake system elements are rusty and that is now somehow a good thing?

And manual transmission cars kinda, though the energy is still wasted of course

Depends on how you drive. I never engine braked on my manual. Brakes are easy to replace. Clutches are not.

You don't engine brake with the clutch, you engine brake by downshifting and using the higher engine RPM in lower gears to brake the car via wasted compression.

And that downshifting involves a clutch operation, moving the engine into a higher RPM. That most certainly wears down the clutch, talking as someone who's replaced quite a few of them.

I've seen an interesting A-B test with this seeing the difference in clutch wear between the Ferrari F1 transmission in the 599 and 612 and the DuoSelect transmission which is essentially the same box in the Quattroporte. The shifting strategy and technique is more of a controlled variable here because the shifting is automatic though it's a somewhat traditional manual gearbox with hydraulic actuation. The QP is a bit heavier but the Ferraris make a lot more power. From what I saw the cars that fared far worse were the Quattroportes, and those that ate the most clutches by far were the ones putting around the city, especially in San Francisco, Marin, Los Altos Hills, etc. where people are slowly creeping into parking spots on hills. On the Ferraris that are weekend warriors that get driven hard the clutches could go 30k+ miles no problem, Quattroportes would come in with smoked clutches in a few thousand miles sometimes.

Everything on the QPs was always breaking.

I've never driven an automatic Ferrari or paddle shifted Ferrari to compare, but the QP that I drove (Ferrari V-8, I think that it even said Ferrari on the valve covers maybe) didn't have anything outstanding about the transmission that I remember. I thought it was a regular hydraulic automatic with a torque converter, so they really did tune it nicely. The robotic Toyotas I could feel. Maybe had they not tuned it so nicely it might have lasted longer?

Only the 2004-2006 and maybe some 2007 QPs came in automated manual. Anything after was regular automatic w/ torque converter.

Sorry, ain't native: Which car use downshifting to help braking? Cannot wire in my brains whether this example is pro-downshift braking or not.

I think their point is that you eat clutch when you slip it e.g. when you’re getting in and out if parking on hills, or in city stop and go traffic. When the clutch is fully engaged there’s little wear even hard-driving, and doing a straight in-and-out does not bother clutches much.

Hence Quattroportes eating clutches like nobody’s business while the harder-ridden higher-power Ferraris don’t.

As such downshifting would not wear clutches much.

And anecdotally I’ve never suffered from or heard of engine braking causing clutch issues.

I semi-daily drive a DuoSelect Quattroporte, but usually in light traffic. The clutch-eating problem is sorta inherent to the car. First off, it uses extra clutch to smooth out shifts in non-sport mode, and you don't always want sport mode because it stiffens the suspension a lot. But even in sport, you can't always get it to behave predictably. So given an experienced driver with both cars in city traffic, the DuoSelect will eat clutch faster than a stick. Some install an aftermarket box (Formula Dynamics) to improve this, but still.

Idk how the Ferraris are different. They're lighter at least. Think they also have a different version of the "Superfast" software.

Anyway... I do engine-brake it. The real brakes appreciate not having to stop that limo by themselves.

Forgot to clarify, there is a clutch-eating problem when driving the car properly, but it's not THE clutch-eating problem people talk about where it dies in 10-15K miles from treating the car as a regular automatic.

I didn't quite get if you think changing gears for the purpose of engine braking wears the clutch more than normal or not. Are you using the force from the clutch to force the engine to go from a low RPM to a high RPM? In cases like that where the difference in RPM is significant, I would press the clutch pedal, then speed up the engine by pressing the gas pedal, downshift, then release the clutch. Rev matching, basically. It does wear the clutch a teeny tiny bit, but not more than any other gear change.

If your comment wasn't meant to imply that engine braking wears the clutch more than normal gearing, if you just want to avoid gear changes as much as possible, disregard this comment. (Although... I'm not sure that that's a valid worry, modern clutches last a LONG time when used properly)

You might not execute the rev-match perfectly every time, esp if you're doing a heel-toe. I think it's also harder on the synchro.

Sure, and I definitely don't rev-match close to perfect every time. I'm just saying you don't have to use the clutch to accelerate your motor all the way from minimum RPM, which it sounded like my parent comment might be suggesting

I think that suggestion was that you're holding the clutch pedal in longer while you bring up the RPMs, compared to upshifting which is faster. The clutch does wear a bit even when "fully" disengaged. But I don't think it matters enough here, just don't leave it like that during a red light.

Are you really shifting so much that your clutch slip in the middle of the shift effects clutch lifetime?

My 300k km Volvo S60 still runs on its original clutch, and I changed the brake pads only once. Engine braking is the way.

Clutch wear occurs when the clutch is slipping so you always want to minimize the slipping time.

Most of clutch wear comes from making it slip, while accelerating from a standstill.

You don't make it slip when shifting gear.

The clutch wear on a standard downshift must absolutely negligible when compared to accelerating from a full stop and especially when compared to slower-that-idle operation, i.e. parking.

Also, I have never ever had to replace a clutch, and I drive my cars way past 100k miles.

Yes but actually no.

It wears the clutch but clutch wear is massively dominated by starts from a stop or other cases where you actively slip it any noteworthy amount so just rowing the gears up and down doesn't do much.

It's a negligible amount, especially if you (or your car) does rev matching. My last car (BMW 328) made it to 300k miles on the original clutch.

Actually you'll get some engine braking by just letting off the gas and stepping on the break. Fuel will get cut off in these cases in most cars (unless you're running a very old carburetor car)

You need not burn your clutch to engine break.

You engine brake every time you lift off the throttle and don't depress the clutch. I know what you mean here of course, but I suspect your driving habits are saving you less than you think.

Yep, years ago I had a friend with a VW Beetle and he'd never use the brakes unless he had to. I thought it was cool and carried the story with me. One day I mentioned it to a mechanic friend and that was his exact response. I've never changed a clutch, but I've changed plenty of brakes and yeah, not hard or expensive.

You don't need to touch your clutch to do engine breaking. If you wear out your clutch by shifting gears you're doing something wrong

engine braking does not have any effect on the clutch, other than while downshifting, which if you're blipping/rev-matching has practically no effect

Exactly, if your clutch suffers abuse when you are shifting gears (unless you're trying to aggressively accelerate of course) you need to rethink what you're doing.

Not saying it's smart but when predictably decelerating on the highway I sometimes shift gears by rev matching and changing without even touching the clutch, for the fun of it.

Same on a motorcycle. My current bike has a quickshifter (for both up and down shifting) but even without one you can shift up and down without ever touching the clutch just by pushing on the shift pedal while blipping the throttle off-and-on (for an upshift) or on-and-off (for a downshift). That’s all the quickshifter is really doing anyway, it’s just quicker at it than you are.

I’d wager bordering on 100% of my clutch use is when coming to a complete stop.

Surprisingly you can get nearly same effect in automatics. I put around 60k miles on my first automatic (after120k+ on my first two cars, manual transmissions) and when i got my brakes checked at 63k they noted my brakes were still "brand new". I do gamify reading traffic to try and brake as little as possible (to help pass time etc), but was still surprised how far this takes you given i do plenty of stop and go traffic driving. This was a v6 sedan so lighter than an suv / truck. I expected it to not work in automatics but it does to at least some extent. I swapped for an EV before taking it the usual distance and curious if anyones pushed further and how far.

No reason for it not to work, even more so if you think to downshift. It’s more common with manual as downshifting is a lot more natural but not fundamentally different.

It’s just trivially easy with electric thanks to regen braking.

Though with modern cars getting heavier if you have a small ICE these days you have almost no engine brake which makes some cases more difficult (unless it’s a mild hybrid with an electric kers like some of the small engined fords). SUVs tend to have giant engines and pretty high rolling resistance, which I’d think would somewhat compensated for their higher inertia.

It’s all about learning your car’s behaviour and planning for it.

I don't know about today's engines, but some early fuel injected engines would actually use more fuel when engine braking. In those early designs spark could not be cut off, so if this extra fuel were not added then the mixture would run very hot and risk pre-ignition and damage. I don't know about carbureted vehicles.

It only applies to mechanical injection and carburettor engines. With electronic injection, which is the norm since the 80s, this is not a problem.

It's not "nearly". It's exactly the same effect. Compression braking. Even if you're not on the throttle the engine is still rotating as it's connected to the wheels. If the engine is rotating it is compressing air. If it's compressing air but not igniting fuel (throttle closed) then it will suck energy out of the wheels to compress the air.

You can do it in an automatic, you just have to force it to select a lower gear using the gear number options (1, 2, 3, 4) or using the tiptronic mode. The lower gear means the engine will displace more air in the same amount of time, increasing the rate it pulls energy from the wheels.

People think you can't do it in automatics because they try very hard to keep engine RPM low where the effect is diminished.

If it takes energy to compress the air in the cylinder - doesn't it also release most of that energy when that compressed air is expanded on the subsequent stroke?

If you release the compressed air without pushing the cylinder down you would lose that energy, but you would need a extra device to do so (by lifting a valve at the right time). This option does exist for large vehicles like trucks as a compression release engine brake [0], but this isn't something you'd have on a family car.

In a petrol engine you always want the same ratio of petrol to air in the mix that is taken into a cylinder. As you want to vary the amount of fuel, and therefore power developed, you have to be able to therefore limit the amount of air that is sucked in. Otherwise the engine would always run at full power.

There is a mechanical restrictor called a throttle plate that lives inside the throttle body that restricts how much air the cylinder can pull in (and therefore how much fuel is injected to get the same fuel/air mix). This is controlled by the throttle. When you are coasting, this plate is in its most closed position. This creates significant resistance on the intake stroke, and is where the majority of energy is lost during engine braking. This is also known as a pumping loss.

Diesels always intake the same amount of air, so they can compress it enough to autoignite the fuel. They vary the amount of fuel injected to the same volume of air. This means no throttle body or plate, so unless an extra exhaust restrictor has been added there is minimal engine braking on a diesel engine.

[0] https://en.wikipedia.org/wiki/Compression_release_engine_bra...

What everyone is missing is that a petrol engine is sucking against a vacuum behind the throttle blade.

It's basically like an air compressor that just keeps running despite hitting max pressure and every pump just goes out the blow off valve.

You're right. Petrol engines are air pumps so I should've realised the explanation wasn't correct.

Though the ECU would be doing the AFR management on modern EFI engines as the injectors aren't vacuum operated like Carburetors were. You should be able to cut fuel injection when coasting in a modern engine, can't run lean if there's no fuel at all. Not sure if carbs could do the same.

On all the fuel injected engines I have owned there is a physical cable that controls the position of the throttle plate. There is an airflow mass sensor the other side of the plate to measure the amount of air and therefore how much fuel needs to be injected. So interestingly in these sort of engines you're really just controlling airflow to the engine rather than fuel/air mix like on one with a carburettor.

More modern engines have electronically controlled throttle plates, and this is definitely somewhere you could do something clever like you suggest - cutting fuel flow but also maximising airflow when there is zero throttle input.

I assume engine braking is generally considered a beneficial thing by manufacturers, but it could be fun to be able to customise the amount. Or do something like have the braking come on gently at first then harder. Maybe even try and have a linear or flat response curve vs. engine rpm.

> cutting fuel flow but also maximising airflow when there is zero throttle input

You don't want to do this. Much of the engine braking effect is from pulling the intake air charge past the mostly closed throttle plate. On a car with a wide open throttle plate [even with no fuel], the engine is acting more like a spring than a damper. On the intake stroke, it will pull an intake air charge past the small restriction of the open intake valve(s), then compress it on the compression stroke, then release that compressed energy on the "power" stroke, then exhaust it past the small restriction of the open exhaust valves. Pushing air past the valves will cost energy, but it's not much.

This is why diesel trucks' engine braking works differently. (Diesels don't have a throttle plate.) They can open the exhaust valves to prevent the energy recovery in the "power" stroke to create a higher net braking force. Jake Brake: https://en.wikipedia.org/wiki/Compression_release_engine_bra...

> Or do something like have the braking come on gently at first then harder.

You can do this by letting go of gas pedal slowly. I have "current amount of fuel used" info in my car (liters/100km), it shows pretty clearly, that when going fast and slowly letting go of gas, amount of fuels slowly goes to 0. If I let go of gas fast, the engine is intelligent enough to not close throttle as fast as possible, still probably takes 1 second.

> More modern engines have electronically controlled throttle plates, and this is definitely somewhere you could do something clever like you suggest - cutting fuel flow but also maximising airflow when there is zero throttle input.

They cut fuel flow and close throttle plate almost completely but still allow some small amount of air, in order to actually do engine braking. If you need to coast, you can apply clutch in manual. Don't know that much about automatic, but from what I've driven, they use "lift gas" as a "engine braking" signal, so probably they can't really coast that good.

I've got both at the moment on my two Hondas. Both manual, one with a throttle cable and one with throttle-by-wire. There's quite a bit of difference in how they handle off throttle. The cable will just slam the throttle shut if you just jump off the pedal (obviously) and it jerks pretty hard. The throttle-by-wire car hangs the throttle a little when letting off and doesn't just immediately start decelerating. Then it's much smoother once it does start slowing down. The ECU definitely doing something to smooth it out.

Funny because the cars build dates are only 2 years apart, 2005 and 2007, and they're both K20 engines but the engines handle so different.

The ECU is doing that because rapid changes in state are bad for emissions. Letting you just slam the throttle closed could result in a tiny, but measurable at OEM scale, amount of extra fuel going half burnt out the tailpipe. Slamming it open can cause too lean combustion and oxide byproducts which.

The OEMs try real hard to prevent this because the amounts of emissions byproducts that aren't water or C02 they're allowed to produce are on the order of single digit grams per multiple miles (you can mentally file it as "about the baseline air quality in urban areas" though the rules are hugely more complex than that) so these edge cases matter.

An idling I4 has about 10 injection cycles per second. And the ECU clocks injection time corrections at least at that rate, more likely at double that rate or more. So I think that the smoothing is mostly there for the owner's wellbeing, not emissions.

> it could be fun to be able to customise the amount

Some recentish motorbikes have an option to customise the amount of engine brake, I suppose cars could have something similar, too.

An aside on your last point: In the D gear, a lot of auto transmissions will be set up to allow for the wheels to spin somewhat independently of the engine (in any gear) when you aren't accelerating, which accounts a lot for how well an automatic will coast when you release the throttle, even if you're not going fast enough for top gear (especially apparent with older four speed boxes).

Using the numbered gear options will enable clutches/bands that provide more engine braking.

Huh, interesting. I had thought it was just from the higher gears being used. Vast majority of my driving is with manual, I've only really driven modern autos with 5+ gears (and a Toyota hybrid, which don't really have gears at all).

Auto trans downshift is designed for long hills, not downshifting frequently to stop signs etc like you'd do with a stick.

Even with paddles, there's a delay, or it briefly goes neutral, or it doesn't rev-match well. Or you can't double/triple-downshift, which is worse when you have 8-12 gears. Allegedly wears them down faster too, which idk but would not be surprised if it were true given how unhappy it feels.

It depends on the implementation. I ride an automatic motorbike which will downshift if I grab the brakes a bit harder, even if I'm only slowing to a speed to which it wouldn't otherwise shift.

For example, if I brake somewhat hard from 130 km/h to 90, it will downshift from 6th to 5th. When riding normally, it would stay in 6th down to around 50.

Many modern automatics are smart enough to do this for you if you tap the brakes while rolling downhill.

I'v bee downshifting manually with automatic especially when riding downhill. The effect with Chrysler T&C 2009 was very noticable and effective.

Toyota Sienna 2015 - the braking effect is unfortunately minor.

Many hybrids are not driven to max regenerative breaking. You need to drive and look ahead to make good use of the regeneration. Short distance breaking is still fast and using the discs.

Hard braking is an insane power. Eg. A typical 4,400 lb car emergency stopping from 80 mph has a braking power of 940 horsepower.

Hybrid cars have smaller motors, inverters, and battery packs - and none of those components can absorb 940 horsepower!

A 2nd gen prius battery for example has a max in/out of 30 horsepower.

Always sketches me out using regen for a serious grade decent while laden or towing. I have a sneaking suspicion that one day it's gonna error out and disable itself because too much power and I'll be down to just normal brakes.

It will disable itself if your battery is already full...

Some cars it's quite an abrupt change from the regen braking to the hydraulic brakes.

I have not seen many if any Hybrids that use regen to the same degree as an EV.

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