Mazda’s Latest Patent Shows A Supercharged Two-Stroke Internal Combustion Engine Design

Seems like Mazda is up to something new and exciting with their concept engines. A while ago, a patent filed with the European Patent Office hinted at an RWD vehicle with the Wankel engine and hybrid engine. Now, a patent filed with the United States Patent and Trademark Office points at a two-stroke engine with a supercharger. The discovery was made by MotorTrend. The patent was filed on February 3, 2022, and is tagged as US 2022/0034265 AI.

The patent hinted at a supercharged two-stroke engine that comes with a unique performance cycle in addition to the way a two-stroke engine operates. The engine does so by behaving as a compression-ignition engine under low loads, and then as a spark-ignition engine under higher loads. The spark ignition part is what runs a gasoline/petrol engine, and the compression-ignition tech is found inside diesel engines.

The current SkyActiv-X engines from Mazda use the same high load spark ignition technique, but these engines are not equipped on vehicles sold in the States. The patent also describes using variable valve timing with a higher timing setup while behaving like a diesel engine to maintain a high compression ratio. The variable valve timing will reduce when the engine operates as a petrol engine at higher rpm levels. The higher timing at lower load levels will maintain the necessary compression required when it starts to behave like a gasoline engine, which will have to reduce to prevent engine knocking.

Coming to the supercharger, the supercharger will be used to drive the exhaust mixture out after combustion and to make space for the next combustion cycle. The supercharger is driven from the crankshaft. This is an useful addition, as the intake and exhaust valves of a two-stroke engine open at least half at the same time which is responsible for the lower efficiency of the engine. A supercharger will force fresh air into the engine when the exhaust gases are pulled out.

Two-stroke engines were the technology of the past, and their high emissions and lower efficiency rates made them obsolete for usage on four-wheelers. However, dirt bikes, and machines like a leaf blower or chainsaw still make use of a two-stroke setup. But Mazda does mention ‘improved fuel economy’ in the patent, but an improved fuel economy in what context? There is no mention of a reference to compare the emissions to. Also, the emissions from a two-stroke engine are higher.

The supercharger will help drive the unclean mixture out, but it needs to be filtered as well before it is let out into the free atmosphere. The patent again mentions an oxidation catalyst and a particle filter, but also adds that the current model does not include a NOx catalyst; and that it might be equipped with one. The reason a NOx filter is important as in a two-stroke engine, there is no exact method to control the air-fuel mixture’s stoichiometric ratio that can control the emissions. This is another effort by the company to keep ICEs running, despite the entire globe slowing shifting towards a more efficient method of mobility: electric vehicles.

Like with patents, there is no surety as to what will happen with the patent, but this idea of a new combustion engine is still a welcome move by many enthusiasts. There is a possibility that the patent engine might act as a range extender for a hybrid EV, but the 2022 Mazda MX-30 is already equipped with something similar. The patent might make it to production, or may just be another addition to Mazda’s intellectual properties collection.