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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

#311

Post by D-Coder »

okdood64 wrote: post #277
freeone3000 wrote: post #225

Earlier quoted context omitted.

>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.

I have never based a car purchasing decision on how much noise the car makes.

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

#312

Post by cout »

rpmisms wrote: post #208
MrDunham wrote: post #205

Earlier quoted context omitted.

Friendly correction for others because your auto correct failed you... "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.

That fuel is totally depraved, and has no hope of salvation.

This is why TULIP oil makes a great fuel additive.

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

#313

Post by cout »

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…

This edit is brilliant!

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

#314

Post by adrianmonk »

> To do this, Porsche's patent shows a crankshaft spinning on a ring with two concentric circles—an annulus. ... this engine has two top and bottom dead centers.

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.

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

#315

Post by bob1029 »

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…

> 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?

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.

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

#316

Post by rpmisms »

cout wrote: post #312
rpmisms wrote: post #208

Earlier quoted context omitted.

That fuel is totally depraved, and has no hope of salvation.

This is why TULIP oil makes a great fuel additive.

I totally, unconditionally, agree. My own limits do not account for the irresistibility of this combination. I hope you persevere with this message.

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

#317

Post by _yb2s »

dahart wrote: post #209
_yb2s wrote: post #199

Earlier quoted context omitted.

When Porsche says efficiency they mean making more power, not using less fuel. Porsche has a long track record of adopting efficiency tech and using them to make fast cars that still use a ton of fuel.

What’s the difference between getting more power out of a given quantity of fuel, versus using less fuel to achieve a given power output?

Porsche cares a lot about efficiency, because with higher efficiency they can make more power. They are a sports car company, and ultimately are building high performance vehicles. That is in contrast to other less performance focused car companies, which would use efficiency gains to allow them to use a smaller engine- thereby making it both more fuel efficient and cheaper/lighter, but not faster.

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.

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

#318

Post by _yb2s »

OJFord wrote: post #246
_yb2s wrote: post #199

Earlier quoted context omitted.

When Porsche says efficiency they mean making more power, not using less fuel. Porsche has a long track record of adopting efficiency tech and using them to make fast cars that still use a ton of fuel.

I'm not sure if that's supposed to be a correction, but if so I don't understand. The description of the two new strokes is as an addition to the normal four, one of which is the fuel intake, I was not assuming that decreases in quantity or anything. It could do, it's just orthogonal to the point - if you don't entirely combust whatever amount you inject in the first ignition , then the idea here aiui is to compress…

It is not a correction, but additional context. Indeed Porsche cares about efficiency- but there are different ways to then leverage that efficiency- for either a more powerful car, or a more fuel efficient car. Porsche will choose the more powerful car, because they sell sports cars, not economy cars. Also see my other reply in this thread.

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

#319

Post by _yb2s »

dahart wrote: post #218
serial_dev wrote: post #214

Earlier quoted context omitted.

Extremely simplified, when you drive a sports car, you want to maximize power (work per unit of time), period, you don’t care about fuel. 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 liter…

Those are correct statements that don’t answer the question I asked. You’ve explained the difference between not caring about efficiency and caring about efficiency. The article said the 6-stroke design is for “efficiency” and did not say Porsche doesn’t care about fuel and only wants to maximize power, contrary to the comment I replied to above. If an engine gives you more power with a fixed quantify of fuel, then i…

Porsche cares a lot about efficiency, and their cars are generally designed to be very efficient- but they use the extra efficiency to sell a more powerful car, not a more fuel efficient car.

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.

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

#320

Post by xcv123 »

thebruce87m wrote: post #146
xcv123 wrote: post #144

Earlier quoted context omitted.

Is your country 100% EV now?

No, but even if it was demand would still be lower than 2002: > The highest peak electricity demand in the UK in recent years was 62GW in 2002. Since then, the nation’s peak demand has fallen by roughly 16% due to improvements in energy efficiency. > Even if we all switched to EVs overnight, we estimate demand would only increase by around 10%. So we’d still be using less power as a nation than we did in 2002, and th…

That’s better than I thought. But you still need to ensure that power source is clean, otherwise it defeats the purpose.
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