Porsche Receives Patent for Six-Stroke Engine

Unless you drive an early Saab, your car probably has a four-stroke engine. Porsche, however, believes that more strokes would be better.

The automaker has applied for a patent entitled “Method for a Twice Three-Stroke Combustion Machine,” or six strokes, which AutoGuide first spotted on September 12 by the U.S. Patent and Trademark Office (USPTO) after Porsche filed its application in February.

The term “stroke” here refers to the up-and-down movement of the engine piston in the cylinder; in a four-stroke engine, air and fuel are drawn into the combustion chamber, compressed, burned (also called the power stroke), and exhausted to convert energy into rotational power Power To complete the cycle, this movement must be performed four times (or two revolutions of the crankshaft). A two-stroke engine, such as a lawn mower, accomplishes this with only half as many strokes, or one revolution of the crankshaft.

The engine design described in Porsche's patent application increases the compression stroke and power stroke by one by varying the stroke length. This is made possible by an eccentric gear that allows the piston to deepen its bottom dead center and increase its stroke. This exposes the scavenging ports and allows more air to be drawn in. More fuel is then injected and ignited. [A six-stroke engine has two power strokes, while a four-stroke engine has one power stroke. In other words, the power stroke is performed every three revolutions of the crankshaft, rather than every four revolutions of the crankshaft as in a four-stroke engine.

Whether such an arrangement can meet current emission standards is a big question, and like many patent applications, this patent may never be implemented in a production vehicle. However, engine technologies such as variable compression ratios, once considered too fussy to work in the real world, have been implemented in production vehicles as automakers pursue even lower emissions. So you never know.