Mazda Patents Fascinating Supercharged Two-Stroke Engine Design

Mazda now has patent for a two-stroke supercharged engine design in the United States. This is interesting because a two-stroke combustion power plant is not something you find in any modern car. Today, you are more likely to find this type of mill in a leaf blower or chainsaw.

As if the engine’s two-stroke combustion cycle wasn’t interesting enough, there are more features that make this one interesting. At low loads, the power plant runs on compression self-ignition like diesel and can then switch to spark ignition combustion when under higher loads.

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The Mazda patent also mentions the use of variable valve timing to maintain a high compression ratio when operating under automatic ignition such as diesel. The timing will change when using spark ignition to reduce the compression ratio to prevent knocking.

If any of this sounds familiar, it’s because Mazda’s Skyactiv-X engine is also capable of transitioning from compression self-ignition to using spark plugs depending on conditions. In some markets, automakers are selling Mazda3s with this powerplant.

The patent says the two-stroke supercharged engine has improved fuel economy but doesn’t say what layout compares to those improvements. Higher exhaust emissions are generally a major drawback for two-stroke plants, and the documentation does not indicate whether this design offers an advantage to the problem.

The filing provides no clue as to Mazda’s intentions for this engine. It’s hard to imagine automotive applications unless this design has significantly better emissions and fuel economy than traditional two strokes.

Dirt bikes are one of those places where two-stroke engines are still quite common. One possibility is that Mazda could license this design to motorcycle makers.

With any patent, it is always possible for engineers to invent something new and decide to patent the idea. No intention for production. Instead, companies just want to protect intellectual property.