Porsche's Idea for a Six-Stroke Internal Combustion Engine Looks Brilliant

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.

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