AS IF THE INTERNAL COMBUSTION ENGINE ISN’T COMPLICATED ENOUGH - PORSCHE ADDS TWO MORE STROKES - RECOMPRESSION & RECOMBUSTION
Porsche, never one to follow convention, has filed a patent for a six-stroke engine. Yes, you read that right - six strokes. That’s two more than your typical four-stroke engine and the real kicker? One of those extra strokes is another power stroke. More power, more efficiency, and, inevitably, more complexity. So how does it actually work? The best way to understand this engine is to think of it as a hybrid between a four-stroke and a two-stroke design. It still has an intake, compression, power, and exhaust cycle like a regular four-stroke engine, but Porsche has figured out how to sneak in an additional compression and power stroke.
Here’s how the six strokes play out in one cylinder:
Intake Stroke – Air and fuel enter the combustion chamber.
Compression Stroke – The piston compresses the mixture.
Power Stroke – A spark ignites the mixture, forcing the piston downward.
Secondary Compression Stroke – Fresh air enters through special ports.
Secondary Power Stroke – The air-fuel mix ignites again, creating more power.
Exhaust Stroke – Spent gases are expelled, completing the cycle.
The magic trick here is the use of two different top dead centres and two different bottom dead centres - meaning the piston doesn’t just travel up and down like a traditional engine but follows a more complex motion. This allows it to expose intake ports at a specific moment to introduce fresh air for that crucial second power stroke. To make this work, Porsche is using what’s called a hypocycloidal crank assembly. Instead of a traditional crankshaft where the pistons just move in a straightforward up-and-down motion, this system adds an offset circular motion. The result? The piston has three distinct peaks and valleys in its movement - two high points (top dead centres) and two low points (bottom dead centres), the key to unlocking that second power stroke.
The most obvious benefit is more power. More power strokes per cycle means more energy output. A four-stroke engine has three power strokes in 12 engine strokes and a two-stroke engine has six power strokes in 12 engine strokes - Porsche’s six-stroke engine lands somewhere in between, with four power strokes in 12 engine strokes - about a 33% increase in power over a conventional four-stroke design. So if Porsche applied this tech to something like the 911 GT3’s 4.0-litre flat-six, which currently makes 500 hp, the same displacement could potentially push 600 hp - without forced induction. That’s a massive power bump for a naturally aspirated engine. Of course, it’s not all sunshine and extra horsepower. Porsche isn’t quick to list drawbacks, but a few challenges stand out like the cost & complexity with more moving parts, a complicated crank system, and unique valve timing that makes this a nightmare for mass production and repairs. More power strokes could mean more emissions and there could be heating issues, as well as lubrication problems. Will it ever see production? Who knows, Porsche patents a lot of cool ideas, and not all of them make it to production. For now, it’s a glimpse into the kind of engineering wizardry Porsche is cooking up.
Take a look at the YouTube video that goes into great detail to explain the new 6-stroke combustion engine that the tech boffs at Porsche recently unveiled to the world. It's a lot to follow, but if anyone can help someone with only a Matric understand, it's Jason Fenske from the aptly-named Engineering Explained: Porsche's 6-Stroke Engine Is Genius! | Engineering Explained
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