Posted on 09/23/2024 1:19:26 PM PDT by Red Badger
The patented engine design features a special crankshaft that adds more power and compression strokes to the cycle.
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Porsche has revealed a strange (and possibly brilliant) idea for a six-stroke combustion engine. If you don't know the fundamentals of an internal combustion engine, we'll try to keep this simple. If you do know how engines work ... we'll still try and keep it simple.
With very few exceptions every combustion-powered car uses a four-stroke engine: intake, compression, power, and exhaust. The intake stroke is where air and fuel come into the cylinder. Compression is when the piston pushes that mixture to the top of the cylinder. The mixture is ignited, shoving the piston back down for the power stroke. Exhaust is the final step, pushing the remaining gas out of the cylinder.
Porsche designers reckon they can add another compression and power stroke to this process. Documents filed with the US Patent and Trademark Office specifically describe this as "six individual strokes that can be divided into two three-stroke sequences." The added steps would occur between the traditional power and exhaust stroke. The first sequence, then, would be intake-compression-power, followed by compression-power-exhaust.
To do this, Porsche's patent shows a crankshaft spinning on a ring with two concentric circles—an annulus. This alternates the center point of rotation, effectively lowering the piston's travel (bottom dead center) slightly for the added strokes. That in turn changes the compression, since the piston isn't traveling as far up (top-dead-center) in the cylinder. And that also means this engine has two top and bottom dead centers.
Why all the complexity? In short, this design has the potential to generate more power with better efficiency. In a typical engine, only one stroke in four actually makes power. This changes the formula to one stroke in three, and it also burns up the mixture more thoroughly. Of course, the downside is added complexity. Whether the gains are enough to justify the design remains to be seen.
As with many patents, it's possible this could never see the light of day. It's certainly an interesting idea, but perhaps more importantly, it suggests Porsche is working very hard at finding ways to keep combustion engines alive amid the push for electric power.
https://youtu.be/bQ9eeQwa7v0
Ping!....................
K. I. S. S.
interesting concept ... article doesn’t give enough information for a really valid assessment. The second power stroke seems to be dependent upon a lot of inefficiency in the first power stroke. Is this correct? Is there enough unburned fuel and oxygen in the cylinder after the first power stroke to even make a second power stroke?
Sounds like another ludicrous idea to meet the ridiculous CAFE standards. The auto makers will do anything to gain another 0.1 mpg.
I saw a YouTube video yesterday that taught me something I didn’t know. I always thought that auto timing belts ran dry. But about 40 years ago, a company called GAS in Germany build a wet-belt engine with the belt exposed to engine oil. That car was acquire by BMW and became their 3-Series. Lots of makers adopted the wet belt. The author of the video says it has been a disaster everywhere it’s been tried (lots of car makers adopted it) with greatly reduced timing belt life and increased belt breakage failure.
I forgot to add that the wet belt was adopted in recent years to improve fuel economy. The video author said the lubrication on the belt does improve economy about 0.1% (I think he said) which equates to about Euro 15/year in Europe. But car owners are faced with HUGE bills to change out their failed belts. So the regulators and makers are happy but the consumer is screwed because of the arbitrary and capricious fuel economy standards set by the government. The car owner saves maybe Euro 45 over three years but has to pay Euro 800 to change out the failed belt.
Remember to replace your timing chain.
“K. I. S. S.”
Uh, we’re talking about Germans here. “Simplicity” isn’t necessarily on brand for volks who use words up to five-dozen letters long.
engine timing is going to be a nightmare...
Timing belts should have never been introduced.
Review
“intake, compression, power, and exhaust”
or as a lab technician in an engineering class I took described it
suck, squeeze, bang, blow
almost 40 years ago and I still remember
“ The second power stroke seems to be dependent upon a lot of inefficiency in the first power stroke. Is this correct?”
Yes. At the end of normal power stroke the piston drops deeper and pulls in a bit of fresh air. The normal exhaust stroke after that becomes a second compression stroke, albeit compressing a little less than a normal compression stroke. What it’s basically doing.. per my understanding.. is spreading out the *Total* combustion time across two strokes instead of one giving the fuel a little more time and a little bit more air to burn. On paper it might mean a a little more efficiency and maybe their tests show there is measurable improvement. I don’t know.
I see you understand the Germans, have almost certainly worked on German machinery.
I appreciate you finding this stuff Red. I personally am not giving up on the ICE.
That would seem to suggest an overly rich mixture for the first power stroke, with the excess fuel to be burned by the second power stroke.
Of course, the downside is added complexity. …Of course the article had to say this in the second-to-last paragraph. Can’t fight thermodynamics.
I’ve got a ‘14 Ford Expedition with the 5.4L Triton engine. Only 103k on the clock. It is interesting that Ford does not have a predetermined replacement interval in the owner’s manual or service schedule for the timing chain on this engine. It is engineered to last the engine’s lifetime under normal operating conditions.
“Timing belts should have never been introduced.”
I agree. Chains do stretch, but they last a LOT longer than belts.
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