Video: Driving a Skyactiv-X prototype

Here are our first impressions from behind the wheel
by Paulo Rafael Subido | Jun 19, 2018

When new technology is thrust upon the average motorist, one of the first tests is whether it can go by unnoticed. In something as sophisticated as Mazda’s Skyactiv-X engine, this makes perfect sense. Its engineers tell us that when the mill is working as it should, it will be imperceptible—save for the improvements over the current generation. And let me just get straight to it—Skyactiv-X delivers on its promise of improved response from the get-go.

Before we got to drive the black prototypes, we got to do some baseline testing around the Mine Proving Ground using current-generation Mazda 3s in both automatic and manual guise. Slipping into the driver’s seat of the Skyactiv-X prototypes was a revelation. There is plenty of torque from very early on in the rev range, and once at cruising speed, the engine reacted very quickly to even the smallest bit of throttle input. In other words, the car felt alive and very eager to get up to speed. We like that. The engineers also say that this type of driving fun can be had without any penalties at the pump. In fact, there was a display mounted on the dashboard that indicated what mode the engine was operating in. 

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Improvements were made with the chassis as well, with a vehicle architecture that ‘optimizes the ability of the human body to balance.’ This is done by making the seats firmer and more rigid, yet maintaining the S-shape curve of the human spine. To relay feedback to the driver’s bottom better, the seat moves together with the sprung mass of the chassis through areas that have been reinforced. In other words, a more direct connection with the road is made. However, for added comfort, road input or energy that is channeled through unsprung mass is transferred smoothly to the sprung mass. That’s some engineering wizardry right there.

Now back to the Skyactiv-X engine, which takes the best characteristics from gasoline (spark-plug ignition ) and diesel (compression ignition) motors. The end goal is to have cleaner emissions without sacrificing power and driving fun. Homogeneous Charge Compression Ignition (HCCI)—gasoline combustion achieved through compression alone, like a diesel motor—is not new, but Mazda is the first to commercialize this with its Spark Plug Controlled Compression Ignition (SPCCI) method. The initial challenge was to improve efficiency during lean-burn technology, which has its own set of limitations. A lean air-fuel mixture, though efficient, is harder to combust and needs more heat and pressure. The big breakthrough over at Mazda is the use of a spark plug to adapt to different atmospheric conditions.

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Here’s the simplified formula: The piston design has a swirl effect and positions the densest part of air-fuel mixture in the ideal position for combustion to occur (super clever); a spark-assist ‘fireball’ raises compression; the injection event is  distributed in stages; the entire cycle is closely monitored by sensors in each cylinder to adjust timing of the spark based on ambient conditions (it can even predict when to fire), and seamless switching happens between spark-controlled ignition mode and compression ignition. Do you follow us?

Skyactiv-X uses a high-pressure injection system that atomizes fuel, has in-cylinder sensors, and a high-response air supply through a supercharger (which only activates at specific engine loads). This is a bit to digest because of its complexity, but it’s very fascinating stuff. 

We can’t wait to experience Skyactiv-X in real-world conditions. Stay tuned for that. In the meantime, we hope you enjoyed our brief video. 

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PHOTO: Mazda Japan
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