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Porsche's idea for a six-stroke internal combustion engine

motor1.com

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Re: Porsche's idea for a six-stroke internal combustion engine

#271

Post by _DeadFred_ »

outside1234 wrote: post #266

Reading these articles is like when you used to read articles in 2005 about people "innovating" on OS/2. The market has moved to electric (see China) and Porsche would be well served on investing there versus on OS/2 (nee ICE engines).

It's all in a weird state. Tweaking ICE engines was a fun hobby with lots of 'consume' products to dream about. Electric just out of the box stomps ICE, but not in the same 'acquiring things and putting together a puzzle' type way that feeds our monkey brains.

That said Porsche is dead and the super wide Audi's pretending to be Porsches just because they have a Porsche skin are lame.

Re: Porsche's idea for a six-stroke internal combustion engine

#272

Post by m463 »

outside1234 wrote: post #266

Reading these articles is like when you used to read articles in 2005 about people "innovating" on OS/2. The market has moved to electric (see China) and Porsche would be well served on investing there versus on OS/2 (nee ICE engines).

There was quite an overlap between the use of bows and guns. Bows were reliable, accurate, quiet, would work in the rain and reloaded quickly. Guns took a long time to exceed them.

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.

Re: Porsche's idea for a six-stroke internal combustion engine

#273

Post by locallost »

hnlmorg wrote: post #264
locallost wrote: post #257

Earlier quoted context omitted.

Direct quote: In fact for some use cases they can actually work out both more expensive to run and less environmentally friendly once you total up their carbon footprint in full. End quote. No, once you total up their carbon footprint they make up their additional costs in carbon in less than 20k miles. As far as bikes are concerned, I've never owned a car in my life and I'm 40. Locally I go on foot, bike and rarely…

Exactly. That quote doesn’t mention mileage. You mentioned it. > No, once you total up their carbon footprint they make up their additional costs in carbon in less than 20k miles. You’re being overly generalised. There are different ICE cars that have different carbon footprints. Hybrids too. Different driving styles that can affect fuel consumption too. Just as there are different EVs that have different running cos…

I didn't read much because actually the point about the way electricity is generated was already mentioned. It's right there in the first post - with the electricity grid of yesterday. If you'd followed the link you'd see how it was based etc.

Things aren't really that unclear or case to case either. A person buying a tiny IC car will not suddenly decide to buy a 7 ton Hummer EV where suddenly their carbon footprint is much higher. They will buy a Volt or whatever it's called. So there really is nothing really that important other than mileage. EVs are clearly better in every use case, as long as we're talking about the environment.

And lastly first hand experience in driving and owning a car is not helpful in determining carbon footprint. The research I linked to is helpful. Under 20k miles per car (on average - if it makes you feel better, but please note I am not insinuating it will make you feel better) with the electricity grid of yesterday. As the grid decarbonizes, this will be even less.

More EVs please.

Re: Porsche's idea for a six-stroke internal combustion engine

#274

Post by _DeadFred_ »

kopirgan wrote: post #212

Know nothing about automobile engineering but somehow this feels like WordPerfect releasing a fantastic version for DOS when Windows was already capturing all the market. Btw they did that. Rest is history.

I think it's more like every keyboard player still lusting after physical analog synths even though everyone has perfectly usable, deterministic, digitally perfect software synths for a fraction of the price (or even the amazing free version of Vital).

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.

Re: Porsche's idea for a six-stroke internal combustion engine

#275

Post by DriftRegion »

mpol wrote: post #270
markhahn wrote: post #252

I always wonder about premises in cases like this. a pair of compression-power cycles is a nice way to question the usual. has anyone gone through all the features of a conventional engine and asked: what if there's an alternative? 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…

Since hybrids are now so popular, rethinking how a gasoline engine fits into that picture might be worth it. Question is whether the market will shift again from hybrids to full EV, and if so, when. Designing and building a new engine might cost 5 billion, without a real certainty you will earn it back.

The Obrist Zero Vibration Generator is exactly that: reimagining ICE tailored to series hybrid application.

https://m.youtube.com/watch?v=0s5Du7qrPoM

https://www.obrist.at/powertrain/components/

Re: Porsche's idea for a six-stroke internal combustion engine

#276

Post by 01HNNWZ0MV43FF »

markhahn wrote: post #252

I always wonder about premises in cases like this. a pair of compression-power cycles is a nice way to question the usual. has anyone gone through all the features of a conventional engine and asked: what if there's an alternative? 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…

Cylinder solenoids are indeed a thing

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

https://en.m.wikipedia.org/wiki/Atkinson_cycle

Re: Porsche's idea for a six-stroke internal combustion engine

#277

Post by okdood64 »

freeone3000 wrote: post #225
mrangle wrote: post #223

Earlier quoted context omitted.

ICE aren't niche, and there isn't strong evidence that they will be. There doesn't seem to be a public Come-to-Jesus moment for electric cars on the horizon. There seems to be solid reasoning behind that reluctance. That is, it will be difficult to displace. If phasing out ICE comes down to regulations only, then the antique interface analogy doesn't fit. >On the other hand of the spectrum, Hyundai Ioniq 5 N can emul…

>need to talk about the vanity attraction of a future all electric Porsche 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 electri…

Serious [sports] car enthusiasts don't care about faster; especially not in a straight line.

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.

Re: Porsche's idea for a six-stroke internal combustion engine

#278

Post by ryukoposting »

markhahn wrote: post #252

I always wonder about premises in cases like this. a pair of compression-power cycles is a nice way to question the usual. has anyone gone through all the features of a conventional engine and asked: what if there's an alternative? 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…

Rotating valves exist - look up "spool valves." Much like rotary engines, seal wear is the main drawback. Poppet valves also have the upside that they inherently spread air-fuel mixture out laterally.

Re: Porsche's idea for a six-stroke internal combustion engine

#279

Post by hatsunearu »

i_am_jl wrote: post #201
magicalhippo wrote: post #196

I'm a programmer, not an engine guy. From the description in the article, they do one intake stroke, two pairs of compression-power strokes, followed by an exhaust stroke. 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 u…

>more fuel means less compression is tolerated before knocking 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 lea…

>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.

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)

Re: Porsche's idea for a six-stroke internal combustion engine

#280

Post by hatsunearu »

magicalhippo wrote: post #206
i_am_jl wrote: post #201

Earlier quoted context omitted.

>more fuel means less compression is tolerated before knocking 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 lea…

Ah yes, read that engine knock article the wrong way around, guess my mind was drawing on intuition from things like gun powder where more stuff crammed more tightly together is worse. 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?

Pretty sure it's just a way to get more expansion from the same air charge.

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.

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