Porsche Patents a Six-Stroke Combustion Engine: What Does It Mean?

In recent years, the automotive world has been buzzing about the shift to all-electric vehicles (EVs), with many manufacturers pledging to transition away from traditional combustion engines. However, as time goes on, it appears that the reliance on combustion engines might last a bit longer than anticipated. Petrol and diesel remain an incredibly energy-dense fuel source, making it difficult to move on from, and manufacturers are still pushing the boundaries of internal combustion engine (ICE) technology. One such example is Porsche, which has filed a patent for a six-stroke engine, a new and intriguing approach to combustion.

Instead of the conventional four-stroke engines we're all familiar with, Porsche's patent is for what they call a “METHOD FOR A COMBUSTION MACHINE WITH TWO TIMES THREE STROKES.” This technical term has raised eyebrows, as many would simply refer to it as a six-stroke engine. However, it seems there’s more to the terminology than meets the eye.

To understand the concept, it’s important to first revisit how a typical four-stroke engine operates. The standard four strokes include intake, compression, power (combustion), and exhaust, all completed in two crankshaft rotations. Porsche’s six-stroke engine extends this process by adding extra compression and power stroke, achieved over three crankshaft rotations.

Here’s the breakdown of Porsche’s patent:

1. Intake: The engine takes in a fuel-air mixture, moving the piston from the second top dead-center (TDC) to the first bottom dead-center (BDC).
2. First Compression: The piston then moves back up to compress the fuel-air mixture.
3. First Combustion: The fuel mixture is ignited, forcing the piston down again.
4. Second Compression: The piston compresses the remaining gas mixture as it moves upwards again.
5. Second Combustion: The leftover fuel mixture combusts a second time, driving the piston downward again.
6. Exhaust: Finally, the spent gases are expelled as the piston moves upwards one more time.

The innovative aspect of this design lies in its second compression and combustion cycles. Essentially, the engine re-compresses and burns the same charge of fuel and air twice. This raises the question: is there really enough unburnt fuel in modern engines to benefit from a second combustion cycle?

The engine uses a planetary gearset design to enable this additional compression and combustion cycle, making it a variable-compression engine. While this adds complexity to the manufacturing process, the potential for increased efficiency and power output could make it worthwhile.

Historically, six-stroke engines aren’t entirely new. The first one dates back to Samuel Griffin’s 1883 design, and there have been other six-stroke concepts involving water injection cycles. However, Porsche’s approach stands apart by focusing on an extra compression and combustion process.

While it’s unclear whether this engine will offer significant advantages over current four-stroke designs, it’s certainly an interesting development. Only time will tell if this patent will lead to real-world applications or if it’s merely a strategic move to block competitors from exploring similar innovations. As always, we’ll have to wait and see how it unfolds.

For now, Porsche’s six-stroke engine patent reminds us that the future of combustion engines is still evolving, even as the automotive industry edges closer to electrification.