Porsche's idea for a six-stroke internal combustion engine
motor1.com
motor1.com
Also, it seems the initial compression-power strokes are done with the piston moving lower, ie both lower top dead center and bottom dead center, hence would have lower compression, and the second moving higher so with higher compression.
From my understanding of more fuel means less compression is tolerated before knocking[1], and vice versa.
So do I understand it correctly that their idea then to make the first power stroke rather rich with lower compression ratio to eliminate knock, and the second at a higher compression ratio to burn the remaining unburnt fuel? Or the other way around, ie lean with high compression first?
If so, it seems like an evolution of variable compression ratio engines[2].
edit: my morning-brain is having issues with thinking about how air-fuel ratio change in rich-burning vs lean-burning scenarios. So perhaps they aim for a good stoichiometric ratio and rely on the exhaust gasses to avoid knock when increasing compression the second time around?
[1]: https://en.wikipedia.org/wiki/Engine_knocking
[2]: https://en.wikipedia.org/wiki/Variable_compression_ratio
Generally, no.
Knocking happens from pre-detonation, that's usually caused by heat from compression causing the fuel/air mix to ignite before it's triggered by spark.
To avoid this engines will run a fuel/air mix that is not stoicheometrically ideal, to make the mixture less likely to ignite early.
It is safer to run a fuel rich mix than to run a fuel lean mix as it keeps combustion chamber pressures low (unburned fuel takes heat out of the exhaust). It is more economical and more ecologically friendly to run fuel lean since you paid for that unburned fuel and it's kinda gross.
In general, more fuel than ideal means more resistance to knock. But these things are complex.
EDIT: Knocking happens from pre-detonation. Knocking can also happen from predestination, like in the case of turbocharged Subarus.
"predestination", pretty sure parent meant "pre-detonation"
A.k.a. Autoignition aka "it goes boom before you planned on it"
Only adding this as it's a pretty crucial word for understanding the comment.
No, it usually happens because the normal flamefront from the spark causes a rise in pressure that triggers compression-ignition in other parts of the cylinder. It's not solely from the compression, usually. That scenario is rare primarily because as you reduce the knock margin, you'd hit knock from what I said before you get to the state where it's so bad it ignites from compression alone.
https://www.researchgate.net/figure/In-cylinder-pressure-tra...
Look at this picture; this is a typical waveform of cylinder pressure vs. crank angle. The spark happens 28 degrees before TDC, so basically the left edge of each of the graphs. As the flamefront consumes the air-fuel mixture inside the cylinder after the spark, the cylinder pressure gradually rises. During knock events, the cylinder pressure as risen by the normal combustion process gets to a point where it starts igniting the fuel elsewhere in the cylinder, away from the gradually expanding flamefront. This causes rapid combustion which causes the pressure to rise suddenly, which causes damage to the engine (if severe enough)
Edit of the week IMO.
I would think the usual cause is the timing was off and the spark plug fires before the cylinder reaches TDC.
So then, if they're doing a non-ideal initial burn it would have to be a lean lower-compression burn, followed up by a higher-compression secondary burn?
It's a similar idea to the Atkinson cycle. You have dissimilar compression and expansion strokes. In normal engines, there's a limit to compression ratio because if it's too high, it causes knocking. But a bigger expansion ratio lets you extract more energy out of the combusted gas, which leads to higher efficiency.
The original Atkinson cycle idea was to use some complex linkage to get dissimilar compression and expansion strokes, but the way it's implemented in things like the Prius is to have a high compression engine, but mess with the intake valve timing such that you only use a small part of that compression during the intake phase so you effectively handicap your compression ratio to avoid knock, while still retaining the full stroke during the expansion phase.
I think it's safe to assume that the second stroke is burning incomplete combustion products left over from the first stroke. I think that the second compression stroke would have to be higher compression than the first in order to get more complete combustion of what's left behind.
Second stroke goes lower and there are some ports to add air which are not accessed during the initial compression stroke...so the stroke is longer (higher compression) and more air is added to help with the reburn.
Kinda sounds like combining the idea of the Miller cycle with a variable compression/stroke setup (see Nissan).
There are a lot of ideas out there that create gains individually...glad to see them being combined more and more in modern engines. (ex. VRIS, VVT, DFI,) I personally think there is still another few decades of playing around with ICE to be done...not sure it will be viable for the market...but the research will lead to a lot more interesting engineering.
So the first phase is like a regular 4-stroke engine, and the second phase is more like 2-stroke engine, where extra air (and possibly fuel) is introduced into the cylinder, like a 2-stroke, through ports located below the position of the piston during the bottom dead center of the first phase.
So I guess you have something like intake (high), compression (high), power (high->low), compression (low), exhaust (low->high), where in parenthesis is the adjustable piston height?
So a richer higher-compression first phase, followed by a leaner lower-compression second phase?
Unless I screwed up my notation shift, the strokes from the patent are as follows:
1. Intake (low TDC -> high BDC)
2. Compression (high BDC -> high TDC)
3. Power (high TDC -> low BDC)
4. Compression (low BDC -> high TDC)
5. Power (high TDC -> high BDC)
6. Exhaust (high BDC -> low BDC)
So during the first power stroke, stroke 3, the cylinder moves from "high" to "low" and thus is the longer power stroke. Also during the second compression stroke, stroke 4, the cylinder position moves from "low" to "high". So technically leading to higher compression ratio. I was thinking it would cost too much energy to do so, hence dismissed that alternative, but I guess not.
The patent also notes that the extra scavenging ports are not needed, fresh air-fuel mixture can be introduced via the inlet valve(s) while the piston moves between the two BDCs.
Would be fun to try to simulate it in Ange's engine simulator[1].
That all makes sense. Pretty much what I assumed. The compression stroke at #4 is the longest stroke. Then it also has the benefit of the Power stroke at #5 being shorter which will mean it will have the benefit of a short(er) stroke motor on the power (more torque?) during that cycle.
The shorter stroke on #1 is desirable since you are using boost (I am assuming Miller cycle here) to control the beginning of compression as opposed to the intake valve.
Once the mechanical timing is down I assume it isn't too bad to keep all in line though...but a mess if it gets out.
With direct injection they could even be injecting more fuel into the cylinder for the second stroke...but I suspect the second stroke F/A ratio is determined by the first stroke remnants combined with the extra air allowed in at the bottom of the second stroke.
All of this with the cam variators, timing control, boost control and fuel setup that VW already runs would be fairly easy to control with the proper sensors and code.
Just speculating at this point...but it makes sense to me.
Heh all along I'm wondering, what kind of thermodynamic cycle is it? By six strokes, does it mean there are actually distinct new phases to the PV graphs compared to Atkinson/Carnot/Miller?
Or is it just masquerading a well-known cycle underneath six strokes, only some parts are being optimised?
Seems to be like it is a Miller cycle (or could be) on the initial 4 strokes. Which would allow you to control the timing of the "Compression max point" in the stroke by varying the boost. That may also vary the amount of spent fuel remaining for the second "scavenge" stroke...which if I am reading comments above correctly it pulls air from ports lower in the cylinder which would help clear the cylinder for the next 4 stroke cycle.
Seems to me more focused on reburning/scavenging to make a "cleaner" burn than anything else though.
*Not an engineer...just a shadetree mechanic who reads too deep into engine papers.
for instance, what if we're just interested in range-extension? can we transform the motion created by combustion into electrical power in a clever way? cylinder-solenoid coils?
are poppet valves so great? suppose we have some other mechanism to create the motion (solenoids?) or rotating valves? something electromagnetic appeals because it gives complete control over timing (rather than a crankshaft).
rotary engines are appealing, for the same contrarian reasons. but they seem to either have practical problems (wankel) or don't seem to be making it to market (peanut-shaped rotors, etc).
if 6 cycles makes sense (presumably in combustion physics), does it make any sense to burn in one chamber, then move those products to another chamber for some further (potentially different) cycle?
would it help if you could ignite from more than a single place? multiple plugs sounds like a bit of a pain, but could you generate an annular spark? would you want to control the location-timing of the combustion front? does rotating-detonation have any meaning in this context?
are there ways to reconsider the materials engineering of engines? make them dramatically cheaper, lighter? one of the best EV arguments is simplicity, but how much of current IC engineering is based on assumptions that can be broken?
A recuperated Brayton cycle operating at a fixed RPM could be competitive with existing approaches. It is also mechanically feasible to produce engines of this type with a single moving part, zero effective wear and no lubrication.
https://en.m.wikipedia.org/wiki/Free-piston_engine
And the Prius uses the Atkinson cycle which is slightly different from the traditional Otto cycle somehow, although I couldn't find a good explanation
Other than the potential energy of either the heat or the compressed gas, what "power" is created in the compression phase of a normal four stroke ICE?
They’ve got loads of other cool thinking outside of the box solutions. Like the Lightspeed transmission with 7 clutches, providing instant shifting between any gears and ability to slip freely between them.
It would take a severe lack of vision to not be able to imagine that the following will -never- improve: charging infrastructure, charging technology (specifically, charging time), and BEV range
The last mile problem doesn’t negate the fact that for 85% of people an electric vehicle is possible in five years.
Electrification will happen for the vast majority of people. Of course, a small minority won’t be able to make the switch right away and will have to hang on to gas. That’s fine!
Even to this day, 98% of houses have refrigerators. According to your logic, we shouldn’t allow businesses to sell refrigerated milk because of this 2%.
"EVs are faster in a straight line! EVs have a flat/high torque curve!" -- big whoop.
1) 0-60 times are biased against ICEs as their torque curves _aren't_ flat and so the start of range is mostly when the engine is at a disadvantage. In an actual road situation the ICE is already at speed and therefore at or near the peak of their torque curve.
2) Actual roads have these things called "curves". Your bulky heavyweight EV handles like a brick on 3 wheels. And it doesn't have as responsive braking due that weight.
As you might expect, the technology will continue to evolve, too.
The truth of the matter is that EVs win out in so many categories already and are improving year on year.
2: batteries are getting lighter and more energy dense. Your point is essentially moot in an era where everyone is buying giant trucks and SUVs anyway, that they drive with a single occupant to the supermarket to pick up a sandwich.
20240301817
(which can be used on various sites, e.g. https://pat2pdf.org/ to retrieve the document)
Btw they did that. Rest is history.
I think it's a great analogy. It's all the little quirks and flaws that make ICE cars feel like they have a 'soul'. The more you have to engage with it, the more it feels human and machine are having a conversation. Many car enthusiasts seek out manual gearboxes (despite being slower to 60mph than a modern auto), because it's _fun_ and gives you some mechanical sympathy.
I own an EV, which is a fantastic daily, and a 911 for weekends. I've never felt like taking the EV out for no reason other than to enjoy a mountain pass. It's too heavy in the corners and too sterile.
Yes manual steering and gearbox are fun. The response is linear predictable.
But if I were a kid entering college I'll be scared to choose automotive engineering as it's mostly likely to be wasted knowledge..
On the other hand of the spectrum, Hyundai Ioniq 5 N can emulate a sports car with an internal combustion engine and 8 speed sequential gearbox.
>On the other hand of the spectrum, Hyundai Ioniq 5 N can emulate a sports car with an internal combustion engine and 8 speed sequential gearbox.
Sports cars are sometimes for vanity, which is a role that a Hyundai wouldn't fill. But you referenced driving characteristics. Fair enough, and so no need to talk about the vanity attraction of a future all electric Porsche. When not for vanity only, sports cars are for people who like a driving experience. Sports car culture is strongly critical of any deviation from an ideal experience even with better ICE cars. Therefore, it tends to detest "the other end of the spectrum" the most.
Sports cars are integrating electric motors, but mostly as horsepower and torque supplements for ICE. The most well regarded sports cars for the common man err toward being ultra-light weight, relatively low power, and high rpm with a manual gearbox. With the rest being as analog as possible. With incremental deviations from that ideal only as preferred for specific owner comfort. None of that criteria speaks to an appropriate / desired role for an electric motor.
Future? You can buy an all-electric Porsche Taycan since 2019 - and it’s faster than the 911.
Sports cars are fully adopting electrification, due to the huge torque numbers and high scalability. M-B and BMW of course, but also Porsche and soon to be Ferrari. It’s not just hybrids used for a boost (as in the decade past): those are full electrics.
I by no means fall into this category completely, but I much rather have a moderately slower car than an electric, with real engine/intake/exhaust noise that handles well on turns.
Kind of, but not really. It accelerates from 0 faster but that's just about it. I don't think anybody would prefer a Taycan on the track versus a 911, and if you were actually racing them, I think the 911 would win every time.
Again, "faster" isn't the most important metric for car enthusiasts. Which is what I described in my post. I know that's disappointing to people who would like it to be in order to claim total justification for electric motors.
To say that "sports cars are fully adopting electrification" seems to want to imply that sports cars are moving mostly to full electrification. This isn't remotely true. Their customer base wouldn't stand for it.
I own a 2014 Boxster S. 315 hp, 266 lb/ft torque, 6-speed. It is NOT the fastest car out there. In fact I own an automatic 3-series BMW that's faster in a straight line every time.
But the Boxster is under 3k pounds curb weight. It is laser-precise on the road. And it sounds glorious, especially with sport exhaust.
I'm often driving between 20-35 mph in second gear because it's the best day-to-day way to hear the engine's sounds.
Otherwise, there are people out there buying 911s/etc. because they can rather than because they care, and those people don't care that Porsche is moving sports cars to hybrid, or less interested in putting manuals in their cars.
But lots of us still want the pure sports experience.
While I admit its severely wanting and the car will suffer for the abuse on the turns, I can get the edge of that feeling in an old Corolla simply due to the weight and connectedness. While the much faster and newer luxury cars are numb (yet have their place for commuting and highway driving).
It's why older (inherently bare bones) Lotus's are still $50k, ancient Honda S2000's are $20k, and new Miata's approach new base trim SUV prices.
It's why you love your Porsche. And it's why a new Porsche GTS4 Rs (double clutch aside) sells for $100k over sticker new or used, is $100k over the cheapest comparable McLaren in the used market, and why it's very difficult to get one new. Just for example.
All electric sports cars have been a thing for a while, even at the supercar level. Car enthusiasts have in fact embraced electrics. Go on youtube and look up drag race comparison races and a Model S Plaid is very frequently the one people want to beat.
Double clutched automatics have taken over h pattern manuals.
You citing the appearance of the Model S Plaid at "youtube drag races" reflects more of your lack of understanding than my own.
The double clutch vs manual debate isn't relevant to the one under discussion. Its an interface argument that is more niched than ICE vs electric, is specialized to each particular car, and each particular use and driving preference.
No it's just a simple example of how attitudes are changing. You'd expect the drag/Hoonigan crowd to be ICE diehards, but instead they've embraced electrics as interesting and worthy competition.
You asserted that the sportscar world would "detest" any change away from ICE, when clearly that's not what we're seeing.
Porsche and others are embracing all electric platforms. Even hypercar manufacturers like Koenigsegg are embracing hybrids as a transitional technology.
Then look at the cutting edge stuff like the Perry Sterling and it's obvious electric race cars have a bright future indeed. Look at the electric cars and bikes running exhibition at Pikes or Isle of Man. People in the racing world are excited about these developments.
> The double clutch vs manual debate isn't relevant to the one under discussion.
You're the one that mentioned manual gearboxes in your comment.
For the common hobbyist/enthusiast electric vehicles are still mostly looked down on regardless of make/model. I don't know how many times I've heard some variation of "it's really a shame that company X made the spiritual successor for model Y as a hybrid/electric/automatic" and old ICE cars that cost a fraction of the price of even an electric supercar get more crowd attention at meets.
I think it's a combination of a few of things. For one, "raw" driving feel is still pretty much unmatched though this has much to do with older cars not having as many creature comforts / driving assists as newer cars do and not entirely an ICE vs electric issue outside of losing the manual gearbox and engine sound. Tuning/modding is also pretty much incomparable between the two- you will never get as much customization / feeling of a unique build on an electric car because there's simply far less you can actually tune and/or modify. And finally, cost, most hobbyists can't justify buying a performance oriented electric car at today's prices when an old ICE sports car as a wrenching project is far far cheaper and feel more fun to drive on twisty roads due to the driving feedback.
Yes, EVs are better in a lot of ways, but in 2024 there are severe barriers that make EVs impractical for a lot of people. Throughout most of the world, charging infrastructure just isn't good enough.
Because cities have better charging infra than rural areas, EVs are at their best as commuter cars. Ironically, there was already an alternative to commuter cars that's hypothetically even better than EVs - public transit - and it also suffers due to lack of investment in infrastructure development.
As you can see, compared to 2023, the sales numbers have been worse month for month in 2024, not just in August.
We are talking hobbyists not corporate office software users. ICE is boring to my monkey brain looking to be entertained/engaged even if vastly superior.
- Dyer/Crower engine = 5th stroke compresses air only, then inject cold water into the overheated cylinder and has another power stroke on 6th (from the generated steam)
- Ilmor/Schmitz = the exhaust stroke from two normal 4-stroke cylinders power the down-stroke of a 3rd larger cylinder, alternatively, then evacuates the gas on 6th up-stroke. [1]
[1] https://www.youtube.com/watch?v=muq1xlF8Gu4
PS: For some reason, the Ilmor/Schmitz is call a 5-stroke engine.
Obviously, Porche's target market isn't likely to care about that.
But for possible down-market uses of this technology - are there any mechanical engineers in the house, to comment?
It’s true they’re expensive to rebuild properly but you can get used engines with a lot of life left for just a few k.
Presumably Porsche’s design still has all of that, too.
At the bottom of the first power stroke, the cylinder drops lower to expose scavenging ports. That both forces air in (at the bottom of the cylinder) and helps push exhaust out (through conventional exhaust valves).
Uniflow 2-strokes tend to have high thermal efficiency, but poor emissions, especially particulates. So the idea here might be to gain some efficiency without another emissions-gate.
[0] https://www.caranddriver.com/news/a60914997/2025-porsche-911...
Efficiency in fuel/mile. Efficiency in Power output/liter of displacement.
But that is just my assumption.
You can have a relatively small engine and force a ton of air/fuel into it under boost and get tons of HP but it tends to lose the ability to maintain fuel economy. Tune it for fuel economy and it tends to lose power. It is very difficult to have both in the same package for many reasons. Adding mods like discussed in the article start to allow for the overlap to be wider.
If you want to go the farthest with a full tank, you want to maximize the total work (proportionate to traveled distance) for unit of fuel.
Reality for practically all cars are between these two extremes, you want to enjoy driving, go relatively fast, and still not wasting 25 liters for traveling 100 km.
BTW Porsche makes consumer vehicles, not just race cars. And they make engines for other types of vehicles, not just cars. It’s ridiculous to claim that Porsche doesn’t care about fuel just because they happen to make some race cars. Nothing in the article suggests this design is for a race car, nor would it; a patent is designed to be broadly applicable and if a 6-stroke design is shown to be more efficient than a 4-stroke design for fuel-efficient consumer cars, you can bet Porsche will be happy to sell you the engines or license the design.
Beyond some historical agricultural tractors, Porsche has only ever made high performance cars, they don't make general purpose "commuter" or "family" cars. Even their large SUVs like the Cayenne are very high performance vehicles.
Porsche may well care often about high performance, I’m not disputing that at all. The problem with your repeated statement is claiming they don’t care about fuel efficiency. That’s not what “efficiency” means. They absolutely can get more power out of an engine and sacrifice fuel efficiency, and some of their models do, but if the intent of the 6-stroke design is “efficiency”, then by definition they care about fuel efficiency. Whether they use that to achieve higher power, or lower fuel consumption relative to some other car is irrelevant to what is meant by efficiency. Also you’re just assuming that their 6-stroke design is intended for high performance. You might be right, but there are other possibilities you’ve ignored or haven’t thought of.
You can get a base model with a smaller engine, but it is still a high performance car design from the ground up. They are also pretty small inside- not much more room than a VW Golf. Yes, (wealthy) people take their kids to school and soccer practice in them. I also take my kid to school in my Boxster... which also on paper is slower than a lot of regular Japanese passenger cars, which in practice it could easily lap on a track because it handles so much better.
To really understand the Cayenne, look at a fully equipped model with air suspension, multiple differential locks, skid plates, sway bar disconnects, and a twin turbo V8 - and look at what people on YouTube do with them. Also look at the V10 and V12 Touareg models.
If you're into performance car driving, you will notice that a Cayenne drives nothing like those other SUVs even if the specs on paper are the same. On a track (off road or paved) with a skilled driver it will easily lap those other vehicles. Specs don't account for finely tuned weight distribution, handling, braking, steering etc. that make a Porsche a Porsche, or the fact that all of the systems (oil supply, etc.) can survive sustained high rpm high g-force track use which would destroy other cars quickly.
You are also misunderstanding my point about efficiency- obviously Porsche cares about efficiency, but they don't design or advertise their vehicles to get low fuel consumption. Efficiency factors into the overall vehicle- more powerful, more range, etc. Improved fuel efficiency is also a selling point, but not the main one.
Great, this new claim isn’t wrong, so now we agree. ;)
The base model Cayenne can’t do any of the stuff you described, you’re talking about race-equipped cars, which isn’t what Porsche is selling at the base model. You could argue the exact same thing about almost any car manufacturer; most of them compete in track and off-road races. Subaru would be a great example- their consumer cars share design elements of their rally cars. That doesn’t mean an Outback is an exotic supercar, just like it doesn’t mean that a base Cayenne is either exotic or a supercar. In fact, it’s not. The lowest 2 Macan models are even slower than the base Cayenne. These are just “nice” cars, compared to cheaper brands of family SUV commuters, not high performance cars.
You need to look deeper than the specs at the design and driving characteristics to understand what it is capable of. What makes a Porsche a Porsche is not a low 0-60 time. I have torn down and rebuilt every system on the vehicles, and used them in some of the most extreme conditions on the planet- deep water fording, hundreds of miles unsupported in unpopulated desert, etc. The triple door seal waterproofing and gearbox ventilation systems for deep water fording are alone really unique. You can drive a 20 year old Cayenne deep with water to the top of the grill all day long and not a drop will leak into anything.
A stock even base model Cayenne is one of the few “off road supercars” ever designed and built- and is capable of such things with just the right tires. Of course, some of the rarer factory options radically improve the vehicles capabilities.
I was talking about factory Cayenne options, not race modifications- but the basic design of the vehicle is also really unique to enable those capabilities. For example- other unibody SUVs are mostly on car based platforms, the Cayenne was engineered from the ground up to survive heavy off road use. It is one of the unusual creations of Ferdinand Piech- look up the other vehicles he was responsible for…
I can find some evidence that people called the Cayenne Turbo GT a hypercar, but nobody calls the base model a supercar. Know why? It doesn’t have the engine. You completely dismissed the small family commuter engine. The engine is the primary thing that makes a high performance car high performance, and base Cayenne simply does not have a high performance engine. And so far you’ve ignored the Macan entirely. These base models don’t have the suspension or brakes or other components for good off-roading. People seem to prefer the Turbo with off-road suspension, better brakes, off road tires, and many other upgrades that together more than double the price compared to a base Cayenne.
It’s true that Porsche makes a supercar, like the 911 GT3, but the base Cayenne and Macan models are just widely considered luxury SUVs and nothing more. Maybe Porsche doesn’t make very many family commuter cars, but they do make a few (that happen to sell well because they’re cheaper than sports cars.)
The specs vary a bit, but a 957 for example has a steel spring fording depth of 500mm (19.68") and air suspension depth of 555mm (21.85"). Those specs don't really tell the story though.
Correct me if I'm wrong, but I pulled up the 2024 Forester owners manual- and it has no factory fording depth- and says to never drive through standing water of any depth, whereas the Cayenne manual has detailed specs on depth under different configurations, and even factory instructional videos on fording technique. Few vehicles explicitly have a factory fording rating depth, and if they do it will be well below the actual physical limits to give a margin of safety.
But looking at the specs ignores the massive engineering differences that make the Cayenne extremely good at fording:
-Triple door seals on all of the doors
-Air tight cabin with continuous positive pressure inside (although personally I keep windows down when fording)
-The differentials, gearbox, etc. are all vented way high up on the vehicle with hoses, through ventilation boxes that pass only air pressure and not water
-The engine intake is mounted at the top front of the engine bay behind the grille, with baffles that allow it to keep water out if moving at the right speed, even if you are much deeper than the intake depth with a bow wave over the hood
-Every electrical connector is completely waterproof and submersible
I was once stuck in deep wet mud half way up the doors in one of these vehicles, and it sat there for ~2 hours before I successfully recovered it, and there was no water in the transmission differential, through the door seals, etc. - something that essentially no other factory vehicle could do, even other expensive offroad vehicles.
Moreover, I have crossed some really deep river crossings- such as the Mojave river in the spring after heavy rains. This was much deeper than the factory rating but just below the air intake level, where lifted jeeps were getting flooded and stranded, and it made it through without drowning. There was a drowned Jeep right next to where I entered, that was waiting for an expensive offroad recovery. I was in a completely stock base model steel spring vehicle, with only all terrain tires added.
Look up "Otis"- a stock Cayenne owned by a friend of mine that has driven it 150,000 miles almost entirely offroad, through some of the most challenging overlanding routes in North America. It is not a high end model, and is unmodified other than tires and a slightly better skid plate.
Some fun videos of the Touareg (Cayenne's VW cousin) operating in deep water: https://www.youtube.com/watch?v=GawFxOk2rjc https://www.youtube.com/watch?v=FFO8viLQ5mA
In both of those the water is probably some 35" deep based on going well over the top of the tires.
Now consider that all of this is on a vehicle which also handles like a sports car, and can make good lap times on a race track totally stock- two totally competing engineering goals. It is not the powerful engine options alone that makes it a supercar, but attention to detail for specific engineering goals - to reliably do things other vehicles cannot - from the bottom up. A regular car with a powerful engine is still not a supercar. The Lamborghini Urus and Bentley Bentayga are also both essentially a Cayenne.
They can do unique things, and you pay a huge price for being able to do them- shuttling your kids in something so over-engineered and complex is basically ridiculous- although fun if you can afford it and have other cars as backup. If most of the parts on your car are identical to a Lamborghini Urus which can drive 190mph, none of them will be cheap to fix or replace, even if you have a tiny VW Jetta VR6 engine under the hood. Even just a regular brake job is expensive because the brakes are massive Brembo monoblock brakes, even on a base model.
The Porsche 918 Spyder for example is a plug in hybrid supercar, which uses the hybrid system together with a massive gasoline engine- to make it really really fast.
This is not a new idea but it creates mechanical complexity and higher requirements on the materials of the piston and cylinder.
https://www.autoweek.com/news/a2063201/inside-bruce-crowers-...
edit: Description before link
High power engines exhaust a lot of unburned fuel, because you can't guarantee an exact 100% fill for the cylinder, and there's more power to be had at 120% fill than 80% fill. Oversimplified of course.
It sounds more like they're running fuel-lean, then possibly adding more fuel before the second compression stroke.
Instead of doing this complicated crankshaft, I wonder if you could do this with opposed pistons. The difference between the two top dead centers (and bottom dead centers) is small, so the secondary piston wouldn't have to move far to create the same change in volume.
I can see some advantages and disadvantages. The crankshaft gets simpler, but you need to move the secondary piston somehow, presumably off the camshaft? Which sounds pretty rough on the timing chain. Also, it would have to go where the valves currently are. And another piston ring to wear out.
On the other hand, the crankshaft gets simpler, and it's a critical component since it's transmitting all the engine power. Also, with the opposing piston, you could use a cam to get greater control of exactly when the volume changes happen.
This six stroke is doing something a bit more complex...more impressive, IMHO. Similar in complexity to what Nissan is doing with their variable compression engine they are currently using https://www.nissan-global.com/EN/INNOVATION/TECHNOLOGY/ARCHI...
There was also a 6 stroke diesel a while back that injected water into the empty cylinder after the exhaust stroke to gain an extra compression stroke from waste heat...Bruce Crower (Crower Cams fame) built one years ago but I never heard anything more about it. https://www.autoweek.com/news/a2063201/inside-bruce-crowers-...
They are calling it Budack cycle. https://alexsautohaus.com/whats-changed-with-volkswagens-new...
The market has moved to electric (see China) and Porsche would be well served on investing there versus on OS/2 (nee ICE engines).
I think there is still quite a bit of time left for internal combustion engines.
Long distance is a big one, as is racing. Fuel is lightweight and can still be added quickly.
It has not.
> (see China)
Understand the impact of subsidies.
> versus on OS/2 (nee ICE engines).
There is no roadmap to an electric plane in your lifetime. ICE engines are going to be here longer than you are.
That said Porsche is dead and the super wide Audi's pretending to be Porsches just because they have a Porsche skin are lame.
As soon as they release one with a coal fired steam engine, I'm onboard!
Nothing like last millenniums technology today...