The wankel rotary has been one of the most polarizing engines the automobile industry had ever seen. It produced an absurd amount of power from arelatively compact and amazing sounding rotary set. But it’s also archaic which makes it odd to think Mazda wants to bring it back.
Rotaries are what made Mazda. No power steering, sticky drum brakes, a car so simple you could feel the mechanics in every action and hear the rotary engine rattling loud up front. Next up was a 1984 RX-7 with no traction control. I nearly lost it on the first corner, the car’s tiny wheelbase allowing the wedge to spin like a bottle with the slightest prodding of the throttle. Then there came a second-gen RX-7, and an early 2000s RX-8.
While today this rotary engine has been abandoned by all vehicle manufacturers with the exception of Mazda, that company has not only continued to refine and optimize what it calls its RENESIS rotary engine—which is found beneath the hood of its RX-8 sports car—but Mazda engineers are quite literally taking the rotary engine to an all-new level by powering it with hydrogen. And according to Akihiro Kashiwagi, Hydrogen RE Development Program Manager, at Mazda Motor Corporation, the rotary combustion chamber, which proved to be so vexing for some auto manufacturers, actually has an ideal configuration for handling hydrogen fuel.
The Inner Workings
First of all, know that with comparatively minor modifications, a conventional internal combustion engine (ICE) can handle hydrogen. That’s not an issue. So it’s not that the rotary engine by its nature can do something that one with pistons can’t.
However, in a rotary engine, the intake, combustion, and exhaust chambers are separate from one another. Consequently, when the hydrogen is injected into the rotary engine, there is no premature combustion. In addition to which, the air/fuel issue is more readily addressed by adding an injector to the rotary engine, which is exceedingly difficult to do given the packaging of a typical combustion chamber. These factors, as well as the longer cycle of a rotary engine, means that there is more complete combustion of the hydrogen, which means that there is better use of the available energy.
Mazda’s new hybird version uses the Hydrogen RE system that’s used on the RX-8 hydrogen vehicle, but it includes a series-type hybrid setup, as well. Called the Premacy Hydrogen RE Hybrid—the Mazda5 is known as the Premacy in Japan—the system transforms all engine output into electricity (the rotary engine is directly connected to a generator) and then uses that electricity to drive the permanent magnet synchronous motor to drive the wheels. There is a lithium-ion battery package that stores energy from the generator and the regenerative braking, then supplies it to the motor as required.
We really, really hope the rotary makes a surprise comeback over the next decade. Clubbed with the up and growing hydrogen power technology, Mazda’s latest step in internal combustion innovation could be an interesting one indeed!