Mazda will unveil a new sports car concept at the 2015 Tokyo Motor Show later this month, and there are reasons to suspect that it might include a Wankel rotary engine.

The concept should prove popular with fans of the brand, who have bemoaned the lack of a rotary-engined sports car since the RX-8 departed in 2012.

But this concept could also have implications for those who prioritize fuel efficiency over performance.

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The announcement of this unnamed concept is the latest indication that Mazda is reviving rotary engines.

And just a few years ago, there was chatter about Mazda using these engines as range extenders in future plug-in cars.

In 2013, we saw a range-extended electric Mazda 2 prototype that used a small rotary engine to charge a battery pack.

Rotary engine

Rotary engine

The car used a front-mounted, 100-horsepower electric motor for propulsion.

But it also had a tiny 330-cc rotary engine mounted under its rear cargo deck--capable of increasing range to 300 miles on the Japanese testing cycle.

The setup was similar in concept to what is currently used in the BMW i3 REx. The engine's tiny gas tank meant it was only a supplementary power source.

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The Audi A1 e-tron concept from the 2010 Geneva Motor Show also used a rotary engine as a range extender.

It had an electric-only range of just 31 miles, with the range extender adding 124 miles.

The Audi concept was a fitting use of the technology, considering that rotary engines were first brought to market by NSU, which Audi bought after the smaller German firm collapsed.

2011 Mazda RX-8

2011 Mazda RX-8

Rotary engines are more compact than piston engines, but are also generally less fuel efficient and produce higher levels of emissions. Although they have advantages as range extenders as they can more easily run on a wide range of fuels, be packaged in a smaller space than piston engines with comparable output, and start (and run) with less vibration.

And perhaps because cars like the RX-7 and RX-8 have made them such a big part of its image, Mazda still seems committed to rotaries.

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Mazda president Masamichi Kogai recently said the company has a team of engineers working on these engines.

Mazda will soon need to sell plug-in hybrids to comply with California emissions standards.

That puts at least some of the pieces in place for a production plug-in car with a rotary range extender, but Mazda has yet to disclose its actual plans.


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