While all manufacturers make similar announcements for new products, Mazda’s announcement was something special. This new engine will be the first commercial gasoline engine to use compression ignition. Compression ignition is used all the time, but not in gasoline engines. Diesel engines use compression ignition. When the diesel piston goes up in the cylinder, it compresses the air in the cylinder several times. Compression ratios vary from a low 15:1 to around 23:1. This squeezing of the air makes it very hot. When the diesel fuel is injected into the cylinder, the hot air ignites the fuel instantly. Compression ignition in gasoline engines isn’t quite as simple as in diesel engines, but it does offer similar advantages. Mazda is utilizing a proprietary combustion method called Spark Controlled Compression Ignition which allows the engine to have a seamless transition between conventional ignition where the fuel is ignited by a spark plug to compression ignition where the fuel is ignited by the heat of compression. While details of how the compression ignition works, it is safe to say that the shape of the piston head and combustion chamber will be critical along with the timing and position of the injection of fuel into the cylinder.
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