The last time Mazda sold a turbocharged rotary engine in the U.S. was 1995, in the third-generation RX-7 seen above. (The RX-8, which kept the rotary alive until 2012, never had a turbo.) The automaker has been repeatedly teasing us with rotary-powered concepts and rumors of a Wankel return, but the rotary's poor fuel economy and dirty emissions have prevented it from making a triumphant market return.
But a recently-published Mazda patent shows that the automaker may have hit upon a design change that could bring the turbocharged rotary back to dealerships. Or so we hope.
, the patent, filed in August 2015 and made public a few weeks ago, describes an altered intake/exhaust layout that's perfect for turbocharging. The new design puts the rotary's exhaust port on top of the engine, pointing up, with the intake port directly below and drawing from underneath the engine housing.
This intake and exhaust orientation is spun 180 degrees from the traditional layout used by Mazda basically since the start of its long rotary experiment. As described in the patent filing, which you can read in full below, the exhaust-on-top layout provides a straighter, shorter exhaust path to the turbocharger, allowing for quicker turbo response and a more efficient conversion of exhaust heat into turbo energy. It also has the added benefit of more compact engine packaging, already a strength of the Wankel setup.
Now, this development alone doesn't promise a return of the rotary. There are plenty of hurdles for the spinny-triangle engine, challenges that have flummoxed Mazda for years. But traditional piston engine makers have had some major success with hot-inside-vee turbo layouts, which move the turbocharger as close as possible to the exhaust ports of a conventional vee-layout piston engine. This setup makes the seemingly inevitable move toward small-displacement turbocharged piston engines a bit more palatable, thanks to sharper throttle response, prodigious torque, and excellent off-boost fuel economy.
It's promising to think that we could realize similar improvements in a rotary setting. Because, man oh man, do we miss those turbo-screamer Wankels. Of course, we have yet to see if such changes could bring the rotary wailing back to the market. But we can hope.