Casual Friday: Combustion Redefined

Mazda has been getting a lot of attention the past few weeks because the rumor mill was talking about a spark less gasoline motor. While that rumor is not completely accurate, it is not far off. Here is their video for a short explanation of the Skyactiv-X engine. Underneath the video I have gone into further detail to how this works, as this engine is fascinating I really want to talk about it.

What Mazda has done, is develop their Skyactiv-G (gas) and Skyactiv-D (diesel) engines to the point of near perfection and was able to merge the two into a gasoline powered, primarily compression ignited, motor. They needed to do this, as the fuel efficiency target required a 14.7:1 air fuel mixture (created with the help of a supercharger), the problem with this in a conventional gasoline motor is that such a lean air fuel mixture becomes an unstable burn, which is where the compression ignition is necessary. 

What is known as HCCI (homogenous charge compression ignition) is essentially a Diesel motor. However this is limited to low rpm engines (a Cummins 6.7 Diesel has a red line around 3000 rpm). As you saw in the video, the Skyactiv-X's uneven piston actually creates two combustion chambers, allowing for some help from a spark plug ignited combustion for higher rpm's. 

The benefit of this motor is that it has up to a 30 percent gain in torque over the current Skyactiv-G motor as well as up to 30 percent fuel efficiency gains at lower rpms and 20 percent at higher rpms. For the record, thats a massive jump, a respectable increase in fuel efficiency is usually 3-5 percent, the Skyactiv-X is truly ground breaking. Those numbers are compared to todays currently in production Skyactiv-G motor, if we were to compare the Skyactiv-X to Mazda's MZR motor from 2008 its actually a 40 percent increase in fuel efficiency. 

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Mazda's Press Release: