Mazda revives rotary engine for Toyota’s self-driving fleet

Mazda revives rotary engine for Toyota’s self-driving fleet
An employee attaches a Toyota Motor Corp. badge to an automobile hood at the company's factory in Burnaston, U.K. The company is tapping Mazda's experience with rotary engines to help power its driverless automobiles. (Simon Dawson / Bloomberg)

Mazda Motor Corp. stopped selling rotary engines in 2012 after spending nearly half a century trying to perfect them. The company is reviving the classic technology in what seems like an unlikely place: battery-powered, self-driving vehicles it’s developing with Toyota Motor Corp. to deliver everything from pizza to people.

Mazda will provide rotary engines to run generators that recharge the batteries for Toyota’s in-development driverless delivery fleet, Masahiro Moro, president of Mazda’s North American operations, said in an interview.

“This is a very suitable engine to run a generator because it’s compact and lightweight, with no noise or vibration, and it has very good fuel economy,’’ said Moro, speaking on the sidelines of the North American International Auto Show in Detroit.

Rotary engines need just a handful of parts to orchestrate the burning of fuel and removal of exhaust inside a single combustion chamber, while traditional engines use an array of pistons, valves and crankshafts to coordinate these tasks in multiple chambers. But after decades of trying, Mazda couldn’t lower emissions from its rotary-engine sports cars enough to satisfy regulators, so it stopped selling them.

Instead of powering the entire vehicle in Toyota’s fleet, Mazda’s rotary engines will function as the kind of “range extender” that General Motors Co. pioneered in its 2011 Volt. The vehicles – which Toyota said last week it would develop with partners including Inc. – will need lots of electricity because Toyota plans to customize them to function as everything from mobile emergency command posts to traveling hotel rooms.

Toyota, which has a 5.25 percent stake in Mazda, is partnering with the carmaker to build a $1.6 billion, jointly run vehicle assembly plant in Huntsville.

Mazda and Denso Corp., a supplier in which Toyota has a controlling stake, are helping develop engines and mechanical underpinnings for the electric cars Toyota and Mazda are developing together, Moro said. The companies are studying, among other things, whether to use rotary engines as range-extenders on more than just the e-Palette self-driving delivery vehicle, Toyota spokesman Brian Lyons said.

(Contact the reporter at [email protected].)

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