Mazda SKYACTIV-X: Reinventing the Gasoline Engine

At the Mazda Tech Forum in Frankfurt, I was able to drive two prototypes of the Mazda3 Sport powered by the new 2.0-litre four-cylinder SKYACTIV-X engine. With this mill, the manufacturer has reinvented the internal combustion gas engine by integrating certain diesel engine features to increase torque and reduce fuel consumption and emissions.

In a nutshell, it’s a gas engine that functions much like a diesel engine, minus the harmful emissions.

Low fuel consumption and superior torque
On a mixed bag of city streets, secondary roads and two autobahn sections (without speed limits and where the traffic was sometimes heavy), I drove these prototypes full-bore as evidenced by the maximum speeds of 171 km/h (automatic gearbox) and 164 km/h (manual gearbox) and the average lateral acceleration of 0.6 G and 0.5 G.

Despite my more-aggressive-than-usual driving, my average fuel consumption was 15.5% better in the manual prototype and 13.4% better in the automatic. Exclude the highway segments, and the fuel consumption in town and on secondary roads was 17.9% and 14.7% better, on the manual and automatic respectively. How is that possible?

Several technical innovations
Basically, Mazda’s newly developed gas engine includes numerous innovations. A combustion system known as HCCI (Homogeneous Charge Compression Ignition) helps trigger combustion through compression as with a diesel engine. This engine’s compression ratio is 18:1, which is superior to that of a diesel engine, the air-gas mixture is reduced compared to a conventional engine and the air intake is boosted by a supercharger.

Unlike a diesel engine, each cylinder is equipped with a spark plug that creates a fireball to increase pressure and favour combustion in certain conditions. Mazda calls it “Spark Controlled Compression Ignition.” The spark also acts as a factor in combustion control depending on how the engine is being used, whether it’s being pushed to the limit or on a relaxed ride in an urban setting.

Remarkably, this engine performs better and is more efficient when it runs on regular gasoline versus super, as regular’s lower octane facilitates combustion by compression. Moreover, this technology can be calibrated for several engine types and capacities, which is very promising for the future.

Extreme temperature testing on the way
Mazda has made a very significant technological breakthrough with its SKYACTIV-X engine, which will continue to be developed for several months before it’s featured in production models. What’s next on the agenda? Test drives in regions where the temperatures are very high, like California’s Death Valley, and in northern climes where temperatures are much lower in winter.

During my test drives of both prototypes, I found engine torque very abundant and ever-available, but I noticed a slight lag a few times while driving at a constant speed on secondary roads. This is a sign that there is still some work to be done on engine calibration. Despite this minor issue, I was very impressed by the SKYACTIV-X engine’s output, and by the modifications made to the Mazda3 Sport’s platform that will be integrated into the next generation of the car.

On a global scale, Mazda is a small manufacturer. However, their R&D engineers are constantly innovating and channeling their energies into highly specialized projects, like the development of this SKYACTIV-X engine. This very well structured approach has also attracted the attention of Toyota, who chose Mazda as its partner for the joint development of electric-powered models by 2019.