Live data from Hacker News

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

motor1.com

351–360 of 367 posts

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

#351
I like the old 6-stroke engines better:

- 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.

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

#352
post #341
post #335

Earlier quoted context omitted.

The Cayenne (and also the VW Touareg which is it based on) is an offroad exotic supercar platform from the bottom up- the handling, engineering, etc. is really unique. It is also, by now, and outdated design that is over 20 years old and not changed very much. It is also a very heavy vehicle with a suspension and chassis that can survive hard offroad racing- jumping it large distances, and landing it hard, etc. The f…

> 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 wo…

You are only seeing how it is used by people that can afford something exotic they don’t need or use and not understanding what it really is engineered for- sort of like concluding the Jeep Rubicon must be a cheap commuter car because they are popular as rentals in vacation destinations where nobody goes offroad. Or seeing urban people wearing arcteryx hardshells as raincoats, and not realizing they really are functional mountaineering gear.

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…

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

#353
post #352
post #341

Earlier quoted context omitted.

> 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 wo…

You are only seeing how it is used by people that can afford something exotic they don’t need or use and not understanding what it really is engineered for- sort of like concluding the Jeep Rubicon must be a cheap commuter car because they are popular as rentals in vacation destinations where nobody goes offroad. Or seeing urban people wearing arcteryx hardshells as raincoats, and not realizing they really are functi…

The Cayenne’s max wading depth is just shy of 20 inches, about the same as Subaru Forester.

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.)

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

#354

Earlier quoted context omitted.

I drove stick for a couple of decades. They were fun at the time (except in traffic jams), but I'm no Luddite. I can enjoy being thrown back into my seat with roller coaster acceleration without the accompaniment of vroom vroom noises, exhaust, and shifting.

I did test drive a Tesla and i agree any electric motor does the throwing back better than combustion. But being thrown back is not the fun part. The fun part is controlling the car around those bends on a mountain road. Anyone can floor it in a straight line.

The model 3 is a track car [0], literally with a tunable track mode. It weighs less than other track competitors like the M3 competition. It is fun in the bends.

https://www.youtube.com/watch?v=oXqxiSZAevY

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

#355

Earlier quoted context omitted.

Model 3's didn't exist in 2012. Did you mean something else? I've driven an M3P for 5 years, and I wouldn't call it sterile. I haven't been cross shopping it with vehicles that cost 3x as much and get only 15% of the mileage, so maybe I'm missing something? But weighing 10% more and taking 20% longer to reach 60 doesn't seem particularly compelling.

If it's the only car you've driven for five years of course it doesn't feel sterile, it's a wonderful car, and nothing against it, but it is not a fun car / "enthusiast" car insofar as enthusiast refers to the thin slice of all automotive enthusiasts that are primarily interested in handling that is dynamic and communicative

> If it's the only car you've driven for five years of course it doesn't feel sterile...

I don't understand what you're trying to say here, but clearly we disagree. To each their own.

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

#356

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…

> caused by heat from compression causing the fuel/air mix to ignite before it's triggered by spark.

I would think the usual cause is the timing was off and the spark plug fires before the cylinder reaches TDC.

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

#357
post #270

Earlier quoted context omitted.

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.

BEVs will never take over in North America. There are too many people spread out or living in places with no hope of charging infrastructure. People are going to balk when they find out they can only charge from a 20A circuit if even that is available.

"Never" is a really long time.

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

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

#358
post #353
post #352

Earlier quoted context omitted.

You are only seeing how it is used by people that can afford something exotic they don’t need or use and not understanding what it really is engineered for- sort of like concluding the Jeep Rubicon must be a cheap commuter car because they are popular as rentals in vacation destinations where nobody goes offroad. Or seeing urban people wearing arcteryx hardshells as raincoats, and not realizing they really are functi…

The Cayenne’s max wading depth is just shy of 20 inches, about the same as Subaru Forester. 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 do…

The fording depth thing really makes my point so I am just going to focus on that. You can't really appreciate the Cayenne design unless you are a person that uses the vehicle in a way that pushes its limits- and have firsthand experience that other vehicles will fail in those same conditions.

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.

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

#359

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…

> and it’s faster than the 911

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.

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

#360
post #287
post #153

Earlier quoted context omitted.

Who says so? Batteries been available for hundred years yet we keep talking about fusion being the future, and we have fission. Which both drive turbines, which are a thing from the past? No? What is joke and when? To me is a joke that we keep heating water to move magnets to get energy in 2024 with all the quantum entanglement, Johnson teleportation, lasers, etc. engineering magic happening around. And we do what? h…

Compressed hydrogen has low enough density that even at dangerously high pressures it would take up most of the luggage & passenger areas of a car, just to get mediocre range. Liquid hydrogen has better density (roughly 2x), but it's still not great, & you're dealing with a cryogenic propellant that's constantly venting explosive gas (so it runs out of gas when parked for ~3 days, can't be parked in an enclosed space…

All of this is very interesting, and I'm aware of the many challenges hydrogen is still facing./ But I think material knowledge is also improving rapidly, so perhaps we'll see some very nice new lattices to safely contain it in some compartmentalized manner. But what I meant about hydrogen was not really about cars, but heavy industry. Heavy industry is hungry and will produce its own solar, then dump it in hydrogen and burn it overnight. Then it can feed the electric cars perhaps.
Post reply on HN