Hybrid and diesel off the cards for a production RX-Vision, but turbocharging could make a return.
Mazda’s announcement of the return of the rotary engine this week was conspicuously free of technical details, leaving big question marks over how Mazda will overcome the Wankel engine’s typical efficiency, emissions and reliability issues.
One seemingly likely solution is for the rotary to play the role of a range extender as part of a hybrid electric drivetrain.
Audi has toyed with the idea with its A1 e-tron concept in 2011, but Mazda has been working on a longer-term engineering project that has widely been seen as the rotary engine’s only chance of an automotive future.
I want to introduce new rotary without electrification first.
The rotary’s suitability as a range extender lies in its relatively compact size and efficiency at the constant low revs required to charge an electric motor, as opposed to the variable engines speeds and high revs used when connected to the driveline as a vehicle’s primary source of drive.
However, speaking with CarsGuide at this week’s Tokyo motor show, Mazda global research and development boss Kyoshi Fujiwara explained why it is important for the rotary to stand alone.
Despite significant efforts from the likes of NSU, General Motors and Mercedes-Benz, Mazda is the only manufacturer to successfully market the rotary as a road vehicle engine, and has been behind numerous motorsport successes including the Le Mans 24 hour in 1991.
As such, the rotary is considered an icon of the brand and the investment required for the new-generation SkyActiv-R engine has largely been justified as an engineering showpiece for the brand.
“I want to introduce new rotary without electrification first,” Fujiwara said.
“If I introduce with both, people will say electrification helped the rotary engine.”
Fujiwara-san dismissed the idea of a diesel rotary, but revealed that SkyActiv-R will likely see the return of turbocharging. “Turbocharger is one of the big contributor for future rotary engines,” he said.
The most recent Renesis-generation rotary that powered the RX-8 until 2012 was turbo-free aside from the limited-production hydrogen models sold in Japan and Norway. However 13B and 20B engines that preceded it in the FD RX-7 and JC Cosmo both used twin-sequential turbos to overcome the engine’s intrinsic torque deficit at low revs.
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