Porsche’s 6-stroke engine boasts double power, higher efficiency

Porsche may be signaling a shift in automotive engineering with recent patent filings for a six-stroke engine, hinting at the potential move from traditional four-stroke engines.

The development could mark a major evolution in combustion engine technology, reviving innovation not seen since the days of the two-stroke cycle.

In this regard, the German automotive company has filed a patent with the US Patent and Trademark Office detailing its plan to develop a six-stroke engine design.

According to the documents, Porsche intends to experiment with adding more compression and power stroke rather than depending solely on the conventional combination of intake, compression, power, and exhaust.

Engine evolution

The key distinction between a conventional 4-stroke engine and a 6-stroke design lies in the cam and valve timing. A six-stroke engine is an advanced design aiming to improve traditional two- and four-stroke engines by boosting fuel efficiency and reducing emissions.

There are two types: one uses a single piston with extra power and exhaust strokes driven by captured heat, while the other uses two pistons, which interact to replace valves or increase efficiency. These designs reduce engine complexity, improve cooling, and may increase efficiency like the Miller or Atkinson cycles.

Porsche’s approach is notably more advanced, marking the most significant departure since Samuel Griffin’s original 6-stroke engine in 1883.

The system behind Porsche’s six-stroke engine is complex, but the basic idea is that the crankshaft operates through two cycles: intake-compression-power and then compression-power-exhaust.

The key innovation is a crankshaft that rotates around two concentric circles, or an annulus. This setup shortens the distance the piston travels, changes the engine’s compression ratio, and creates two top and bottom dead centers, improving overall engine efficiency.

Advancing power efficiency

Porsche’s innovative engine design is driven by one key goal: maximizing power. Unlike traditional engines, where power is generated every four strokes, this new design would produce power every third stroke while making more efficient use of the air-fuel mixture, according to Road & Track.

Additionally, Porsche aims to push the internal combustion engine’s evolution forward. According to the patent filing, there is an ongoing effort to enhance combustion engine performance, focusing on energy efficiency and meeting increasingly demanding operational requirements.

However, the patent offers no details on how engineers address vibrations, harmonic balance, RPM ranges, or other technical concerns that would intrigue those with more hands-on experience in engine mechanics.

This isn’t the first time a six-stroke engine has been developed. Previous designs, like Bruce Crower’s six-stroke diesel engine from a decade ago, added water injection as the fifth stroke, with steam exhaust as the sixth stroke, according to New Atlas.

Another example, the Beare Head six-stroke, uses a second piston as a valve, replacing traditional valves and scavenging exhaust gases. However, some argue it’s more of a modified four-stroke. Another design, similar to Crower’s, uses the middle strokes for water injection and steam expansion.

While six-stroke engines tend to be more complex, they offer potential advantages such as increased thermal efficiency (45-50 percent, compared to 30 percent for typical four-stroke engines) and reduced emissions, much like how four-stroke replaced two-stroke engines globally.