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10-08-2017 | Engine Technology | News | Article

Mazda Unveils Petrol Engine with Homogeneous Compression Ignition

Patrick Schäfer

Mazda has presented the world’s first commercial engine to use homogeneous charge compression ignition (HCCI) in cars. The petrol engine, dubbed "Skyactiv-X", is set to debut in 2019.

The petrol engine will be used in the new generation of an as-yet unnamed vehicle and works like a diesel engine with excess air and compression ignition. With an HCCI engine, the homogeneous lean fuel-air mixture auto-ignites when compressed in the combustion chamber, like a diesel engine. Despite lean combustion, the NOx raw emissions should remain at a comparatively low level and fuel consumption is claimed to be up to 30 percent below that of Mazda’s current petrol engines. 

According to Mazda, this is made possible by a patented combustion method called "Spark Controlled Compression Ignition" (SPCCI): the compression ignition is controlled by an additional increase in pressure generated by the spark plug in the combustion chamber. Spark ignition is therefore only necessary when starting, at very low ambient temperatures and at high rpm according to Jochen Münzinger, head of Press and Public Relations at Mazda. 

Increased lambda for homogeneous auto-ignition

Additional air is supplied to the combustion chamber by a type of compressor. According to Münzinger, homogeneous lean combustion is possible with a lambda of 2 to 2.5. The engineers are keen to ensure a greatly expanded lean operating range and also a seamless transition between compression and spark ignition. Above all, controlled auto-ignition is expected also with normal petrol fuel. The HCCI engine is designed to combine the benefits of both petrol and diesel engines and was often called "Diesotto" in the past.

In October, the engine will premiere at the Tokyo Motor Show where there will be more details. In addition, Mazda has announced the development of a new diesel engine. The next generation of "Skyactiv-D" is slated to launch in 2020. From 2019, vehicles with mild hybrid drive and electric cars are increasingly to be offered, but initially only in regions where renewable energy enjoys a high share of the electricity generated or where driving bans are in force. 

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