Mazda confirms rotary compatibility with Skyactiv-X compression ignition

When Mazda committed to resurrecting the rotary engine in late 2015, it was clearly on the basis of having overcome the Wankel engine’s intrinsic efficiency, emissions and reliability issues. 

But how? The then-rumoured and now production-ready Skyactiv-X compression ignition technology seemed like the only possible solution, but Mazda executives weren’t ready to discuss the still-industry leading technology at the time.  

We had the chance to check in on the future rotary with Mazda’s global engine development boss Eiji Nakai at last week’s international launch of the Mazda3 Skyactiv-X in Germany. 

Asked whether the brand could make a new rotary work without Skyactiv-X, Nakai-san wouldn’t confirm that it was a dependency, but did admit its compatibility. 

“We have this technology to create air fuel mixture, controlling technologies for ignition, so these technologies are even applicable to rotary engine, so you can get the better efficiency.”

This is elementary given that a rotary engine natively relies on high compression to work, while struggling for an efficient burn of the air/fuel mixture on each combustion cycle. 

The fact that spark plug location has always been a compromise with previous rotaries adds even more to this rationale, with the plug being forcibly located outside the combustion chamber to avoid interference with the passing rotor/s. 

Skyactiv-X offers a solution to both of these issues, with compression ignition ensuring a cleaner burn and only relying on a spark plug to trigger the ignition process.   

Reliability is likely to have been sorted by Skyactiv-X’s advanced cylinder pressure sensors and computer power, along with advances in material technology since the most recent production rotary appeared with the RX-8 in 2002.

Then-global R&D boss Kyoshi Fujiwara suggested to CarsGuide that a turbocharger is also likely for the rotary’s return at the Tokyo motor show in 2015, contrasting with what we now know of the supercharger used for the new Skyactiv-X piston engine.

“Turbocharger is one of the big contributor for future rotary engines,” he said at the time. 

Aside from this theoretical sports car application, the use of a rotary engine as a range-extending generator in a plug-in hybrid application is now a firm part of Mazda’s future product plans. However, Fujiwara’s intentions as of 2015 were for the rotary to appear as a stand-alone performance engine first. 

“I want to introduce new rotary without electrification first. If I introduce with both, people will say electrification helped the rotary engine.”

These intentions were supported by recent patent application images, which show a turbocharged, twin spark plug design for an upcoming rotary engine. 

It’s still our hope that a production version of the 2015 RX-Vision design concept will herald the return of the production rotary as the centrepiece of Mazda’s 100th birthday celebrations in 2020.

What would you like to see Mazda do with the rotary engine in future? Tell us what you think in the comments section below.