The patented engine design includes a unique crankshaft that introduces additional power and compression strokes to the cycle
Porsche has introduced an intriguing (and potentially brilliant) concept for a six-stroke combustion engine. If you’re not familiar with the basics of internal combustion engines, we’ll keep it straightforward. If you are familiar, we’ll still aim for simplicity.
With a few exceptions, nearly all combustion-powered cars use a four-stroke engine: intake, compression, power, and exhaust. During the intake stroke, air and fuel enter the cylinder. Compression occurs when the piston pushes the mixture to the top of the cylinder. The mixture ignites, forcing the piston back down during the power stroke. Finally, exhaust expels the leftover gases from the cylinder.
Porsche designers believe they can introduce an additional compression and power stroke to this process. Documents submitted to the US Patent and Trademark Office refer to this as “six individual strokes that can be divided into two three-stroke sequences.” The new steps would take place between the standard power and exhaust strokes. So, the first sequence would be intake-compression-power, followed by compression-power-exhaust.
To achieve this, Porsche’s patent illustrates a crankshaft that rotates on a ring with two concentric circles—an annulus. This alternates the center of rotation, slightly reducing the piston’s travel (bottom dead center) for the additional strokes. Consequently, this alters the compression since the piston doesn’t rise as high (top dead center) in the cylinder, resulting in two top and bottom dead centers.
Why all this complexity? In short, this design could produce more power with improved efficiency. In a typical engine, only one stroke out of four generates power, but this setup changes it to one stroke out of three, allowing for more thorough combustion of the fuel mixture. However, the trade-off is increased complexity, and it remains to be seen if the benefits will justify the design.
Like many patents, this concept may never come to fruition. While it’s certainly an intriguing idea, it also indicates that Porsche is actively exploring ways to sustain combustion engines in the face of the shift toward electric power.
