Could Porsche's Six-Stroke Engine Patent Extend The Life Of Internal Combustion Engines?

What are the two extra strokes of the new Porsche engine?

Porsche’s new patent for an internal combustion engine adds two strokes to the four-stroke engine, for a total of six. The engine works by performing additional compression and power strokes. The compression stroke is when the piston pushes the air-fuel mixture to the top of the cylinder – essentially, to its top dead center. The mixture is then ignited, which pushes the piston downwards – the power stroke. Exhaust is the final step, but Porsche does something interesting with its new engine design.

But why bother with a six-stroke engine at all? The real benefit lies with improved thermal efficiency, up between 45-50%. For context, the widely used four-stroke engines across a variety of applications can achieve around 30%. What this translates to is even more power from every drop of fuel while maximizing fuel efficiency at the same time.

How does Porsche’s six-stroke engine work?

According to the data found in the U.S. Patent and Trademark Office filings, Porsche describes the engine as having "six individual strokes that can be divided into two, three-stroke sequences". The two additional strokes would occur between the traditional compression and power strokes. Instead of intake, compression, power, exhaust, the new sequence will be divided into two consecutive, three-step sequences, the first being intake – compression – power, followed by compression – power – exhaust.

The key feature of Porsche’s six-stroke combustion engine is the way the crankshaft operates. It spins on a ring with two concentric circles (an annulus), which alternates the center point of rotation, lowering the position of the pistons. Essentially, the pistons of Porsche’s six-stroke engine feature two top dead centers and two bottom dead centers, which allows the unit to change its compression in the middle of the six-stroke sequence. During the additional compression and power strokes, the piston travels less due to the altered top and bottom dead center.

How viable is Porsche’s six-stroke engine?

Porsche’s latest patent for a six-stroke engine is the result of constant efforts to keep the internal combustion engine alive. Porsche already did this by introducing the T-Hybrid powertrain for the Porsche 911, but this new engine design could see a wider application. A two-stroke engine completes its two-stroke sequence in a single rotation of the crankshaft, while a four-stroke engine needs two full crankshaft rotations to do the same. The six-stroke design manages to squeeze in two extra strokes through a complex design, which is thoroughly described in the patent 81-page patent filing.

Nissan – already dabbled in variable-compression engines, but the design didn’t quite live up to expectations. Porsche may have cracked the code, but we won’t know until we see the six-stroke engine in action. The biggest challenge that I can see is added complexity and as a result, long-term reliability. The patents are proof enough that the company is working on new ways to keep internal combustion engines alive and with Porsche’s efforts in sustainable fuels, enthusiasts would be able to enjoy a future, not dominated by EVs. The company made that abundantly clear with the Porsche Cayenne, which continues to pack a powerful V-8 even in non-hybrid form. The patents could just be a protective policy so another company won’t implement the same technology before Porsche is ready to do so. The real question is, when?