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One of the more interesting things I did when in Japan for the Tokyo Motor Show was drive a brand new car with a rotary engine.

Yes, the venerable Wankel engine, touted 50 years ago as the logical replacement for reciprocating piston engines, is back on the road again – but in a much different application.

Mazda was long the keeper of the rotary faith. In the 1970s, Mazda sold an entire lineup of rotary engine cars and only completely gave up on them a couple of years ago.

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A rotary engine is approximately one-third of the size and weight of a piston engine of equivalent power output; because it has no reciprocating parts, it runs vibration-free. The problem with rotaries was that they burned prodigious amounts of fuel while producing unacceptable levels of emissions.

No company worked harder on rotaries than Mazda and the effort produced good results on the race track. In 1991, Mazda became the only Japanese car company to win Le Mans and the only one ever to win with a non-piston engine. However, rotary sales were awful.

Now Mazda believes it has found a new application for its rotary expertise. It has stuffed a little rotary engine – attached to a generator and a tiny gas tank – under the trunk of its subcompact Mazda2. It's the "range extender" for its battery-electric car.

Rather than having a conventional four-cylinder engine up front to pour juice into the battery like in the Chevy Volt, the Mazda Demio EV has a single rotary engine, about the same diameter as a medium pizza, lying flat. Even attached to a generator, it disappears under the trunk.

A rotary engine – when it was the only powerplant in a car – delivered terrible fuel economy when the driver accelerated hard and drove fast. But as the power to spin a generator, the little rotary can run at a constant 2,000 rpm, where it's most efficient.

Mazda says the Demio EV will have a driving range of 200 kilometres on a full charge of the battery and another 200 kilometres when the "range extender" kicks in. There's a small test fleet headed for the Japanese market and no plans for full production or export at this stage.

In my test drive on battery power, the Demio felt as sporty as the Mazda2, on which it is based. When the range extender started up, there was an imperceptible whoosh and no vibration at all. If electric cars need range extenders, the compact, quiet rotary makes a great deal of sense.

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Mazda is an interesting company. Based in Hiroshima, it plucked itself from the ruins after the Second World War and went back to work. People I spoke to at the company say the Hiroshima spirit is to never give up. Well, they haven't given up on rotary engines.

Mazda's engineers hint they have made enough new developments on rotaries to make them as fuel efficient as most modern piston engines. Could there be a new Mazda some day that is rotary-powered? Nobody is saying.

However, using a rotary as a range extender might put Mazda back in the game, at least in a limited way. The company believes its new rotary unit also has a place in small generators for home or commercial use.

I was surprised to see that Mazda has continued to develop rotaries even after pulling them from its lineup. I shouldn't have been though, because when you're from Hiroshima, you never give up.

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