Skyactiv-X will end the diesel/gasoline debate forever

An enlightening conversation with Mazda's head of R&D
by Paulo Rafael Subido | Sep 24, 2017

Top Gear PH had the pleasure of sitting down to dinner with Hidetoshi Kudo, Mazda's executive officer in charge of research and development. This was at a time that the international automotive media was going nuts about Skyactiv-X—Mazda's latest breakthrough in engine technology. Had our foreign colleagues known that a small group of Filipino journalists were having dinner with the architect of Skyactiv-X, they would have been green with envy.

This new technology is absolutely groundbreaking because it disrupts one of the main tenets of conventional automotive combustion knowledge. Every car-guy tito knows that gasoline engines need spark plugs; diesel engines (which rely on compression) don't. Skyactiv-X has essentially flipped the script on its head because of its breakthrough. The simplified version is this: Mazda has built a gasoline engine that can combust a very lean fuel mixture without spark plugs—while still using spark plugs. Confused? Let me try again.

Gasoline engine prototypes that can combust ultra-lean fuel and air mixtures without spark plugs already exist. These Homogeneous Charge Compression Ignition (HCCI) gasoline engines are very efficient, but are too volatile, unpredictable, and don't like it when speed and load increase.

What Mazda has created is an engine that does Spark Plug Controlled Compression Ignition. It works by using extremely lean fuel mixtures like an HCCI engine, but over a full range of driving scenarios. It still uses a spark plug, though, but only when fuel mixture is in the 'rich' phase. It gets even more complicated from there, so let's skip to the benefits. Essentially, Skyactiv-X combines the best characteristics of both gasoline and diesel engines, namely a diesel engine's efficiency, torque, and low-end response; and a gasoline engine's power output and clean emissions. Skyactiv-X is the culmination of the evolution of both Skyactiv-G's (gasoline) and Skyactiv-D's (diesel) evolution.

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Kudo-san explains further: “The peak pressure is not so high,” he says. “It is comparable to the current generation engines. Even in a Skyactiv-X, we monitor the knocking. Spark assist happens with every stroke.” He also says that the cost will be higher than the current generation engines, but when considering performance and efficiency, the added expense balances out.

We can't wait to drive a Mazda fitted with the Skyactiv-X engine. It is due to arrive sometime in 2019. And when it does, your tito's mind will be blown.

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