“Inside-out Wankel” rotary engine delivers 5X the power of a diesel
newatlas.com
newatlas.com
Not sure a rotary engine screaming at 6500RPM is comparable here to a diesel with a peak torque at 2000 and peak power at 3600.
> LiquidPiston has been working on these X-engines for nearly 20 years now,
I'm guessing they will never actually release a commercially viable product. 20 years to design an ICE is...too much.
I'm reminded of a linear piston engine (iirc two pistons that just go back and forth without their motion being translated into rotation; one where they were side-by-side moving alternately, the other one where they'd actually move towards each other and share a combustion chamber). The use case for that was to have the pistons move through coils, thus generating electricity. We used to have a flashlight that works with the same principle, shake it to generate electricity.
Depends on the fuel cost.
Like these: https://en.wikipedia.org/wiki/CMA_CGM_Jacques_Saad%C3%A9
Edit: ninja'd!
re 20 years to make a new engine point, compare investment $ in traditional ICE across the car industry vs investment $ into rotary or other alternative engines (the former is order of magnitudes more)
Still, call my interest piqued. I'll keep an eye out for their Wankel-EVs
Mazda won Le Mans 8 times (And we all forgot about it): https://www.youtube.com/watch?v=vZ2cmZJjztI
A 30sec DDG search turned up options that are definitely better, e.g., the AIE 80S, with 15BHP/11.2kW at 5kg or their 225CS, with 40BHP/30kW at 10kg [0]. In contrast, this weighs 19kg to produce 26HP/20kW. The net power - weight for these Wankels is 2.24kW/kg and 3.0 kW/kg vs Liquid Piston's 1.05kW/kg.
While IDK about availability from AIE (it just turned up at the top of the search), I know there are others on the market that are/were available. Meanwhile the LP prototype still isn't available 7+ years after I was first looking at them, and the were suppose to ship "real soon now".
We'll see...
The eccentric shaft does indeed spin at the indicated RPM, just as a crankshaft on a piston motor does.
It's just the rotors move at 1/3rd the eccentric shaft's rate, which is a design feature enabling substantially higher than 7000RPM with little effort.
If traditional carmakers had done that research about 10 years ago they wouldn't be facing such crisis with EVs today. a high-efficiency multi-fuel range extender engine is all we need today but still I cant find many automakers jumping on it.
PS: it would have been nice to see a micro-turbine based generator with high thermodynamic efficiency but my understanding is that need a lot of maintenance so not suitable for consumer applications.
1. US incentives and regulation result in car manufacturers having to shift production from hybrids to EVs.
2. In order to qualify as an EV a vehicle can't have a range extending ICE that provides more than a 50% range increase. There's also a very low limit to the size of the fuel tank.
These regulations have resulted in very few vehicles with ICE range extenders. Existing engines are easily capable of maxing out that regulation so there's no incentive to research other engines.
I think its just institutional laziness & innovators dilemma. Even in last 5 years when it was clear Tesla is starting to rise they decided to sit on their hands and do nothing. Even till last year toyota has been singing BS about hydrogen cars and not enough lithium. they deserve whats coming to them.
https://en.m.wikipedia.org/wiki/Brake-specific_fuel_consumpt...
Which covers a range of RPMs.
..Or you can chose to respond with another one line remark without explaining your thoughts.
So this was your intended comment?
If so, I don't see how it's relevant. The money Toyota 'burnt' on hydrogen stuff has already been spent, it can't be recovered.
And the rollout your imagining would require at least 10x the money to do so worldwide.
Relying on a stock market boost to fund such a huge investment is silly because Toyota doesn't pay the vast majority of their suppliers or their staff in shares or options, but in cash.
Well was the decision to go all in on a entirely new tech (hydrogen fuel cells) was conscious choice by Toyota or not? So you agree that they have capacity to spend investment dollars, right? Now could they spend maybe an order of magnitude less money on improving ICE, Most definitely yes. Its definitely less costly trying to reinvent and entire new scientific field (fuel cells) than repurposing ice engine as demonstrated by companies I highlighted (& many more).
>And the rollout your imagining would require at least 10x the money to do so worldwide.
would this rollout be any less expensive for hydrogen cars, I'd argue orders of magnitude more expensive because no hydrogen infra exists. yet you chose to conveniently ignore it. Also, you are making a strawman here by indicating that I am saying need to fund it with stock-market (go back and read my comment). they dont Need that money to start the rollout, they get rewarded by market when they do it because its a fundamentally better product.
My gut feeling is most of these japanese companies are opposed to electrification because of some other ulterior reason, likely because solar may not be viable in that region & their govts might not be so excited about it. In any case they are about to get their ass handed to them by tesla & chinese EVs because EVs are essentially democratizing the automobile development platform due to its simplicity.
Toyota spent that money years ago. How is that at all relevant to how much they can spend in 2023?
Financial markets are much tighter, so I doubt they could even spend 20% as much without huge shareholder pushback.
All car companies will inevitably have to pivot to hydrogen (or efuels or whatever). It is a matter of when and not if. If anything, Toyota is decades ahead of the competition.
Basically, the Chevy Volt is exactly the car you're describing. It wasn't that great: it had a separate engine that only ran a generator, and would only come on when the battery was depleted. The problem is having a full EV powertrain, plus an ICE driving a generator, adds a lot of hardware, complexity, and cost to the vehicle, and the result was a car that people liked, but just wasn't cost-effective compared to the Prius, or to a BEV.
The Prius can get away with a much smaller battery because it's just a parallel hybrid and doesn't need to drive 50 miles on a charge like the Volt. Batteries are expensive and take up a lot of space. And a BEV can get away with not wasting space and weight on an ICE engine (plus fuel tank), and instead just have a big battery. The Volt basically had the worst of both worlds. Reportedly, the car worked well, but with all that stuff packed inside, it just cost too much, plus it didn't have a lot of cargo space.
https://en.wikipedia.org/wiki/Free-piston_engine
https://www.aquariusengines.com/
https://engineerine.com/omega-1-piston-less-near-zero-emissi... (optimize for power but can be tuned for efficiency)
its nowhere near what a turbine can get (60% about max with heat recovery) but high enough to design around need for large batteries.
edit: formatting
The Atkinson cycle has a longer expansion stroke compared to the compression stroke, resulting in a more efficient conversion of heat to mechanical work. However, this cycle tends to have a narrower range of operation, with less torque and power available at lower RPMs compared to an Otto cycle engine.
Perhaps a more efficient cycle is possible by reducing the RPM/torque range even further, but I am under the impression that a lot has been left on the table efficiency wise.
I don't think Liquid Piston was talking about a 2-stroke version before. That's news to me, and it seems like it would throw out the efficiency/emissions benefits in exchange for more power. Maybe the author of the article was confused and this isn't actually a 2-stroke design?
The main design hurdle has been longevity. Their prototypes in the past only work for a short time and wear out. That's probably just a matter of doing the necessary R&D to figure out the best alloys to make the engine out, and the best ways to lubricate everything. It's not clear from the article if this new version has this solved so it can last a normal amount of time or not.
As a bonus, built in EGR if properly managed.
The engine described here can have its shaft and eccentric bearings externally lubricated, but its apex seals, like those of Wankel engines, seem to be in a situation analogous to that of a piston ring. Unlike either of those, however, they are mounted in the stator, not the moving part, and so may be easier to lubricate precisely.
https://www.cycleworld.com/2015/04/06/two-stroke-motorcycle-...
As you said, 4 stroke has intake, compression, combustion, and exhaust. That's expansion, compression, expansion, compression. It fires between compression and combustion.
A 2 stroke motor has compression and expansion. It fires between compression and expansion. Intake, exhaust, and combustion happen during the expansion phase.
A rotary motor is traditionally 4 stroke, and I'm not sure a 2 stroke version is feasible. The LiquidPiston rotary appears to be a 4 stroke to me, despite the article text.
https://medium.com/democratizing-finance/liquid-piston-insid...
This is likely all part of a pump and dump. That's why it's a weird article.
They've been advertising this heavily of all places on instagram and taboola chumboxes. Obviously none of those people need this engine, they're looking for marks.
How is this revolutionary motor being outdone by a mid-range sedan engine?
> XTS-210 is about the size of a basketball, weighs in at 19 kg (42 lb), and displaces 210 cc.
So you are talking about a 26HP lawn mower.
While the Camry might make more power at its normal size. It would not if you scaled it down to the size of a basketball. I'm guessing it would make 1-3HP at that size.
This is 1hp per 0.46 pounds of engine weight, nearly three times better than the camry engine.
Granted an RC engine runs on a mixture of fuel and nitromethane, and doesn't have any reasonable durability compare to a Camry engine. But it also only costs $200.
it's like RAID, great until the RAID card itself fails
That's a huge difference. The main limiting factor in engine power is mass air flow, not fuel. Engines are as much air pumps as they are containers for extracting expansion from explosions. Nitromethane provides extra oxidizer in liquid form, putting nitro engines in some ways closer to rocket engines in terms of power-to-weight ratio.
Extracting more power is, most commonly, a matter of burning more fuel, which requires more oxygen. This increases combustion chamber pressure, which drives the piston down with more force; that force is converted to rotational torque and ultimately drives the wheels harder, pushing the vehicle forward faster.
More oxygen can be added in any number of ways; less restrictive intake/exhaust parts, larger valves, cams that are more optimized for whatever load/engine speed you want to produce peak power (or are more optimized for output than, say, economy or emissions), supercharger, turbocharger.
Adding fuel is more straightforward: A higher capacity pump and/or bigger injectors/carbs.
You can also switch to pistons that will compress the air/fuel charge more. This also increases combustion chamber pressure.
You can also run the engine at a higher speed, which will often warrant different cams, stronger valve springs, etc. May also require bottom end uprated components that can handle that task (connecting rods, pistons, bearings, crankshaft).
On the subject of bottom end components, depending on how much you increase cylinder pressure, you may need to upgrade those.
You can also increase output power by reducing losses - a lighter flywheel is a common example with enthusiasts.
Every single one of these involves a trade-off. A lighter flywheel impacts drivability; removing intake/exhaust restrictions and adding forced induction components will both make more noise; etc.
These greater forces cause more stress to factory engine components, so generally at a certain level you will need to replace engine internals with uprated parts e.g. stronger rods and pistons.
You can do a chip tune that might get you more HP across a wide range of RPMs, but you won't be as robust, will need maintenance more often, and will likely wear through oil, gas, differentials, clutches, and related more quickly.
There's MANY things you can do that all basically come down to burning more gas+o2 in less time. Higher intake airflow (turbo, supercharger, better/missing air filters, scoops, etc), bored out cylinders for more engine displacement, more gas (increased fuel pressure/pumps), increased RPMs, and decreased exhaust pressure (better pipes, decreased or missing cats).
Trick is, more gas+o2 burned = more heat, more wear, more stress, hotter oil, faster clutch wearing, faster tire wearing, and generally faster brake wearing. Turbos are driven by exhaust, spin at crazy RPMs, increase air intake pressure, and generally are harder on the engine and oil and make cooling more of an issue. Higher RPMs require more precise timing, better valves+springs, better balanced cam shafts, etc. So what might seem like a cheap/easy change like increasing turbo boost from 10psi to 15psi might like a good idea, but have major impact on engine life and maintenance costs. A single blown head gasket from the increased temp, increased vibration, and increased pressure can be very expensive.
Much like CPUs of today, cars are generally designed carefully for their performance level and there's less spare performance left to be easily tweaked. Much like how older CPUs could be overclocked for substantial performance gains. Now both cars and CPUs will throttle if they don't have enough cooling or any of numerous other sensors detect potential problems. It's pretty common these days to see a car with 300hp, but 350hp for up to 10 seconds before the sensors reel you back in.
Go ask your Camry engine to make 100% rated power indefinitely, and see how long it holds up. That's the difference.
A typical car engine is designed to make 30-50hp sustained, and occasionally generate more power for reasonably short periods of time.
An aviation engine, generator engine, or any sort of "industrial" engine is going to be able to sit there, making full rated horsepower, for thousands of hours without any trouble at all.
The XTS-210 can do that?
Our flying club engines in the 172s typically make at least 3000, if not 3500 hours, and I think some of the overhauls at that point have been a "Well... it's still perfectly fine... but..." thing where the board was just starting to get uncomfortable with the hours on it.
And, yes, they spend a lot of time making less than rated power, because of density altitude, but they're still rated for full power operation, and since there's basically no wear going on with an engine in operation (almost all the wear is during starting), there's no real difference there.
It's not until you get into the really large engines where "maximum continuous" is a different thing from "takeoff power." The turbocharged 500s are about the smallest I know of with that sort of rating, and even then I don't think it's all of them. Most of the big radials have that limit, though. If you find a smaller plane with that sort of limit, it's either a possible resonance issue between the engine and prop, or a noise regulation for certification.
As I understand, the reason a typical car engine can’t sit at 100% duty cycle isn’t the engine itself, but usually the cooling and oiling configuration.
Examples:
Looking over the Viking engines, I don't think it's fair to call those "automotive engines," because my read of the description of what they do means they're pulling it apart and replacing an awful lot of pieces. They claim they're "based on" the latest Honda engines, and once you're starting to change the cylinder bore offset, custom hone the cylinders, replace your pistons and conrods, etc, it's no longer a car engine.
On their About page, they themselves say:
> Companies like Honda and Mitsubishi have spent millions of dollars refining and testing. We don’t claim that we can outsmart either company when it comes to the design of any internal running component of these engines. We don't change vital engine parameters around and claim we have different models. The compression, etc. is all stock. Every part is OEM Honda / Mitsubishi, nothing is new aftermarket from unknown origins.
> We start with the most up to date year engines with super low mileage, derived from fender benders across the US. When customers want the information about where there engine core came from and how many miles it had - we have all that documentation readily available to show.
Literally, every one of these engines came out of a car. I think that plainly qualifies it as a car engine.
Marine applications generally means salt water, so they will run at higher power is the salt is what gets the engine eventually not the stress of high power output. Airplane engines are expected to be reliable and so they run at relatively lower power output. There are many small niches in between that have their own idea of what 100% duty cycle is.
This exceeds most definitions of "100% duty cycle".
Most engineering in the US is done in metric units. Then marketing applies a metric to imperial conversion.
I suspect China does more engineering in imperial than the US, both in total an per capita: most things I buy made in America are all metric (cars are all metric except for parts designed in the 1960s and the adapter bracket to make them fit on a modern metric car). Most things I buy made in China are imperial. I don't really know for sure, but that is my impression of industry.
That's why I asked about engineering, not driving. Nobody converts torque to power etc.?
https://www.britannica.com/technology/Wankel-engine
both seem to disagree with your technical definition. at the very least, the colloquial usage is broad enough that adhering to some archaic technical definition isn't sufficient to explain some confusion.
even this wiki article says it's obsolete https://en.wikipedia.org/wiki/Rotary_engine
With a small frame like yours you’d probably be better served by an EV conversion if you want to go down that path.
I don't know anyone who has done the rotary or diesel conversion, though I have driven the zero and know another designer who built an electric motorcycle from scratch. When I say from scratch, I mean sketches, solid works, chassis - the whole 9. Of course, this gets easier at the edges where wheels, handlebars, exhaust, lights, and batteries are abundant.
My daily awareness of his progress was working close to his desk at work, so I'm not sure where it's at today though I recall he was about to transition from chassis to engine at the time - 2016. He was definitely ahead of the curve. Sadly, my skills are in things that we have the luxury of pretending are not bound by the laws of physics. ;->
That is not to say change is impossible, GA's overdue changeover to unleaded gasoline seems like an inevitability. Unleaded gas is already being approved for many of these engines, like new production O-360 engines (which date back to the 1950s.)
That depends on if you're describing the pilots or the ~manufacturers~ Textron. The experimental fleet has been pretty adventurous and it's a fast growing fleet. I think most of the conservatism in GA ICE tech has been driven by the broader issue of consolidation into a near monopoly on the cheaper end of the market. If you have no competition then why bother innovating?
Could this engine be fitted inside the rear wheel to save space and weight as well?
Mazda is doing something that I think is fairly novel, which is almost exactly what you've described. They've scaled down the rotary engine from their RX cars to a single-rotor and put it into their new EV (almost tucked into the front wheel well,) and letting it act as a 70ish horsepower generator for the otherwise battery-powered car to extend range.
On top of that, they make fun cars. With buttons and knobs on the dash!
I'm glad they're still around doing their thing.
IIRC, the Freevalve tech is like a 30% efficiency hack for any ICE you put it on, and it's a part of how Koenigsegg are managing to squeeze 600 brake horsepower out of just a 2L, 3-cylinder engine.
Wesley Kagan reimplemented their freevalve technology on his Mazda Miata, and it's probably the coolest hobby automotive project I've seen in years. https://www.youtube.com/watch?v=E9KJ_f7REGw
Here's a really cool explainer on the transmission - https://www.youtube.com/watch?v=Hvb6J96KiSM
I just feel like Mazda doesn’t get enough credit for the innovation they manage to accomplish at a truly mass produced scale. It's almost like they're too "normal" to get the attention they deserve.
The tragedy of Mazda is that they already make one of the best cars in the world, but machismo / public opinion prevents too many men from enjoying the full glory of the Miata. But on the other hand, Mazda's refusal to move it beyond 'momentum car' holds it back. If they added ~30-40 horsepower to it, it could legitimately be stealing sales from cars thrice its price.
I suspect the answer is because it's more efficient from a MPG perspective to allow the engine to directly power the wheels, at the cost of the extra complexity of gearing. Converting motion to electricity back to motion is lossy, and even more so if you insert battery storage as an additional step.
Putting engines in wheels causes a very rough ride. Even if the engine is light you're still likely creating an order of magnitude more unsprung mass. That's an order of magnitude rougher ride.
But maybe I've understood you wrong.
On the other hand, it exposes a lot of surface area to heat, which gets absorbed by the rotor but isn't used to turn the engine. It's a problem it shares with wankel engines. The advantage over wankels is the extra time air and fuel spends burning in the combustion chamber before the chamber volume expands. It means it gets more time to combust evenly which should help reduce both hydrocarbon and nitrogen oxide emissions.
This is one of those designs that works fine initially when everything is fresh.
Diesel piston engines work fine when everything is worn out and full of goo.
Yes, it does result in a buildup of goo in the intake. No, the engine does not run well in that state. That’s what maintenance is for. Clean out the goo every 50,000km or so and it’s fine.
Modern diesels are very reliable machines, just like modern petrol engines. They’re certainly not the robust rocks they used to be, though. High pressure common rail fuel systems, precision injectors and multi stage turbos are standard issue these days and they all require regular maintenance, clean air and clean fuel to operate properly.
Anyone who thinks the EGR valve should be made part of the rotating assembly requiring a complete overhaul to clean out, unbalancing the assembly until that occurs, needs their head examined.
Take a two-stroke Moster 185 engine: 25 HP at 7.800 RPM, for a 15kg package.
I'd be keen to understand how (if) this outperforms a typical two-stroke.
The only straight-ish comparison I can think of is the Suzuki RE5 vs the GT500, which are same-era motorbikes from the same manufacturer, with roughly the same capacity. The RE5 wins on horsepower (62 vs 44), but weighs about 50kg more.
Wankels are usually excluded from all engine comparisons, because it's a considered a different class...for piston engine marketing reasons.
I sold off my RX8 in 2018 because my fiancee and I moved to Seattle (passing emissions testing wasn't anything special). We needed the money and we had her car, which was more functional. I do miss it.
Did you happen to have an 08+ model with the updated engine and/or remove teh catalytic converter?
In my case, I was taking a trip with my family and my RX-8 was blocking the driveway. We were running late for the flight, so I pulled it out, parked it back in the driveway, and let it idle there for 30 seconds knowing I'm not supposed to shut it down so quickly. But I had people waiting for me and what am I supposed to do, say "Sorry I own a strange car and I need to drive around the block for a bit to let it warm up!".
Of course that flooded the engine, but I didn't know until I got back from the trip. I followed all the instructions to de-flood the engine but it wasn't working for me so I had it towed to Mazda where they probably screwed it up further. It was there 2 weeks before they told me the engine needed to be replaced. They eventually had to fly an engineer from Japan to replace the engine since the dealer apparently had no one capable of dealing with rotaries. I think my car was at the dealer for a good 2 months. Thankfully all covered by warranty.
I loved my RX-8, but it was a pain in the rear. Switched to a WRX and got 50% better gas mileage, more power, more torque, and way more room. This of course bypassed the need to check / refill the oil every other fill up (aka, every 300-ish miles) all while trying desperately not to burn your hand.
Why flooding the car (or frankly doing anything to my RX-8's engine) would require it to be replaced seems ridiculous. The casing of the engine is a solid piece of steel. Removing the ring gears and shaft (which you have to do for cleaning every 100k mi anyway), there's nothing to break.
Ofc, if you introduce the engine to some exotic combustion or get some foreign material in there, you could scar any part of the casing and that would brick the engine.
Other than that, they have emissions like 2-stroke engines because of the incomplete combustion and we have never been able to devise any kind of material to make the apex and side seals last anything like as long as piston rings.
Piston engines are a terrible way to power vehicles, but everything else we've tried is worse.
Turbine engines also have great power density and terrible fuel efficiency, but they are very reliable.
Diesel engines are reliable and fuel efficient but heavy.
This one appears to have improved reliability and fuel efficiency over the Wankel without sacrificing power density.
The issues remain fundamental, and largely unaddressed.
This is completely normal through the 70s and 80s when these engines were popular. We didn't start getting million-miler cars until the Lexus LS400 came out.
The problem with the rotary is heat and the damage it does to other components. The RX-8's engine design was actually bad and doesn't adequately lubricate, but that gets 'fixed' in the last three model years.
The biggest reason that RX-7 owners have seal failures are often due to adding on too much power without adequately upgrading the fuel system. Keep in mind that Wankel engines are absurdly popular in the world of amateur aviation without any of the stigma.
Not sure if that's correct.
Mazda is reviving small single cylinder rotary engine design for HEV by running it at a constant speed with max power efficiency to charge the battery.
Turn it into a portable battery charger...
That’s at about a quarter of the size of this. I bet there’s efficiencies to be had if it were scaled up.
I’m just not sure this is the game changing breakthrough the article’s tone suggests.
AFAIK there's nothing mechanically stopping you from scaling a 2-stroke, but it would very quickly render the immediate area noxious.
But they are simple, lightweight, and easy to shrink.
This is actually a really important point as we are trying to clamp down on VOC/NOx emissions. Ignoring CO2, two-strokes emit way more emissions than cars per unit work. But a 4-stroke engine, in addition to expense, does not lend itself to tools like chainsaws. In theory this engine could fill that niche.
Fuel injected 2 strokes have been around for years now. In saws, the Stihl 500i.
Scaled 2 stroke engines, both with and without fuel injection, have also been around some time. The KTM 300 XC is a very modern example with 300cc displacement, so the same general category as the one in the article. Modern outboards on boats go even bigger.
Yes there’s a push on at the moment to retire the fleet of small 2 stroke engines in older garden power tools. Emissions controls have been tightening up on new tools over the years. Electric tools are rapidly displacing them with lower maintenance requirements and less noise.
There’s a lot more to 2 stroke engine development than just saws and lawnmowers from the 80s, though.