How Mazda's Compression-Ignition Gas Engine Runs Like a Diesel Without Blowing Up

Mazda's Skyactiv-X engine is the first in the world to burn gasoline using diesel-style compression ignition. The result? Amazing power and economy.

Yesterday at the Tokyo Motor Show, Mazda released new info on its highly anticipated compression-ignition Skyactiv-X engine. It's all a bit daunting if you're not an engineer, but helpfully, Mazda put together a short video explaining exactly how this revolutionary engine works.

Essentially, this gas-powered engine can run like a diesel, using compression ignition to burn its fuel. Mazda calls this Spark-Controlled Compression Ignition (since a spark plug is still used to initiate combustion), and it's the first engine that can switch seamlessly between compression and spark ignition, depending on load.

This engine also uses a new, split fuel injection system, and an in-cylinder pressure sensor to keep combustion stable and heat in check. Here's how Mazda explains it:

    The SKYACTIV-X controls the distribution of the air-fuel mixture in order to enable lean burn using the SPCCI mechanism. First, a lean air-fuel mixture for compression ignition is distributed throughout the combustion chamber. Next, precision fuel injection and swirl is used to create a zone of richer air-fuel mixture—rich enough to be ignited with a spark and to minimize nitrous oxide production—around the spark plug. Using these techniques, SPCCI ensures stable combustion.

You can read a lot more in-depth coverage on this tech on Mazda's website, but we bet you just want to know the results. Essentially, a 2.0-liter Skyactiv-X engine provides up to 30 percent more torque, sharper throttle response, and a 20-percent improvement in fuel economy compared with Mazda's current 2.0-liter gasoline engine. And Mazda says that at low speeds, the Skyactiv-X can get even better fuel mileage, thanks to its ability to run a super lean fuel mixture.

Skyactiv-X promises the best of both worlds—diesel fuel efficiency with gasoline emissions and drivability. It'll reach production in the 2020 Mazda 3, whose design was previewed in the new Kai Concept that debuted at Tokyo.

If it all works out, this technology could help internal combustion engines stay relevant even with increasingly stringent emissions and economy regulations.