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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

#321

Post by Grazester »

ithkuil wrote: post #259
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…

Iirc Koenigsegg is using camless valves (using solenoids?)

Yes and no. Their 3 cylinder engine that was supposed to be in their 4 person mega car was to be the first product engine with it. That is no longer the case because rich people didn't like the idea of a 3 cylinder engine in their hybrid mega. As a result they are only producing a V8 hybrid version. Their v8s do not use the free valve.

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

#322

Post by physicsguy »

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…

There was a lot of variation in aircraft engines before jet engines took over. They often used sleeve valves for e.g.

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

#323

Post by hommelix »

adrianmonk wrote: post #314

> 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…

2-strokes opposed pistons engine already has a phase shift between bottom and top crankshaft for spooling purpose. Controlling the position of the top crankshaft relative to the bottom crankshaft seems doable.

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

#325

Post by pokerface_86 »

sheepdestroyer wrote: post #324
pokerface_86 wrote: post #61

Earlier quoted context omitted.

you must be european

Muricah much, or just trolling ? I though that was not the style here

i’m not particularly supportive of people who think fun needs to be vilified and taxed out of existence. it just so happens that this mindset is common among europeans who will never be able to afford a nice vehicle

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

#326

Post by philistine »

kevin_thibedeau wrote: post #310
philistine wrote: post #298

Earlier quoted context omitted.

So North America is limited to its large places? New York isn’t in North America. The last mile problem doesn’t negate the fact that for 85% of people an electric vehicle is possible in five years.

New York is mostly a semi-rural state where long distance travel in a BEV is a problem. One city where most residents don't drive doesn't mean anything.

One city ? One city !?

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%.

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

#327

Post by _yb2s »

nolan879 wrote: post #244
_yb2s wrote: post #198

Earlier quoted context omitted.

I drive a 24 year old Porsche and the engine already has a lot more mechanical complexity than most other engines- especially for their variable camshaft timing system. You’re right that Porsche and their target customers don’t care much. I’d say German engineering culture in general is to make things work better (when new), and not worry about complexity.

I Do Cars did a tear down of the M96 engine from a 986 Boxster S. Seeing inside of them, it makes sense how these motors cost $20K to teardown, rebuild and remedy Porsche's cost cutting in their first water cooled engine. I would own another 986 or 996 in a heartbeat. Tear down video: https://youtu.be/qrkALiq5hTU?si=0OmBKYcim-cflJEy

Thanks! I’m not sure what people expect from these engines- they’re somehow basically the most reliable car engine from that era (they regularly came out at the top of reliability ratings), while still making ~1.5x the power per displacement that was standard at the time. Things like the D chunk failure and IMS failure can happen, but most people will get a reliable 200-300k miles before they do, and the IMS can easily be prevented with a new bearing kit that is fairly cheap and easy to do. The 2.7 Boxster engine had none of the cylinder issues- that’s the Porsche to get if you want low hassle fun transportation IMO.

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.

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

#328

Post by dahart »

_yb2s wrote: post #319
dahart wrote: post #218

Earlier quoted context omitted.

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 vehicl…

The base model Cayenne takes almost 6 seconds to get to 60mph when floored. That’s not particularly fast, even by family SUV standards, it’s comparable to a Honda Passport, and slower than SUVs from Audi, BMW, and Ford, and quite a few others. The Cayenne is an SUV in the first place. What exactly is a publicly available SUV if not a general purpose family commuter car? One of my friends bought a Cayenne to shuttle his kids to school and soccer practice. Porsche absolutely does make a general purpose commuter/family car, and you named it.

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.

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

#329

Post by dahart »

_yb2s wrote: post #317
dahart wrote: post #209

Earlier quoted context omitted.

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 Sp…

Porsche can get more power without higher efficiency. That they’re choosing efficiency means they’re looking for higher power with lower fuel consumption. How they choose to use that efficiency is their business, I’m just pointing out that they do, in fact, care about fuel consumption, and claiming otherwise just because they sell high performance cars, is incorrect.

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

#330

Post by digga3000 »

This article has brought out a lot people to comment who don't know anything about sports cars, but feel necessary to insist they do. It's bad enough that I had to login in to dispell this reoccurring canard:

"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.

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