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Spinning the tale of the rotary engine

I am always happy to receive any correspondence from readers, be it fulsome praise or (as is admittedly more common) stern criticism.

I am always happy to receive any correspondence from readers, be it fulsome praise or (as is admittedly more common) stern criticism.

Sometimes the latter is delivered in ALL-CAPS and contains what can only be described as some pretty naughty language.

Flambé or flattery, I always go back to see if either was actually deserved, to improve such that there's more pats on the back than verbal floggings.

Reviewing the Mazda6 a few weeks ago, I mentioned in passing Mazda's dedication to the rotary engine. To wit: "(Mazda) . . . chased the rotary engine, long after that engine technology proved itself too inefficient for commercial success."

Well. That certainly didn't sit well with at least one fan of the funny little triangle motors, who drew me up sharply for making fun of the greatest engine ever made.

What is a rotary engine? First off, when discussing it in an automotive context, we should more properly use the correct nomenclature: Wankel Rotary Engine. Generally speaking, a rotary engine is actually one of those air-cooled things you find on an early piston-engined aircraft that looks like it's made out of stacks of waffles arranged in a radial fashion.

The Wankel Rotary Engine, on the other hand, is a very odd, very clever piece of engineering dreamed up by one Felix Wankel, German engineer. While Felix was undoubtedly a genius, conceiving and patenting his unique motor while still in his mid-20s, we can't gloss over a somewhat checkered history.

He was a sometime member of the Nazi party, joined the SS in 1940, and was actively involved in wartime production of torpedo engines and the like.

Post-war, Herr Wankel began putting together a prototype engine, culminating in an early model that produced 21 horsepower (this in 1957). 1960 saw the first real practical application of the technology, with the first rotary installed in an NSU Prinz.

NSU is now defunct, purchased by VW and merged with Auto Union to form Audi in the late '60s. However, they can lay claim to having produced the world's first Wankel-engined production car: the 1964 Wankelspider. What a great name.

But what is a Wankel, you ask? Imagine, in cross-section, a block of metal with an oval, slightly peanut-shaped cut-out. Then imagine a fat triangle set into the peanut in such a way as to allow it to rotate just barely, as long as you wiggle it around.

I see those of you with a P.Eng designation have begun weeping. Let's persevere.

In a normal piston engine, the fuel/air mixture lights with an explosion that pushes downwards, turning the crank like a leg pumping a bicycle pedal.

In a Wankel engine, the explosion is the same, but instead of up-and-down motion, it actually spins the three-sided rotor around inside the chamber. Advantages? Compact size, very smooth operation, incredibly fast-revving, good power output if you measure displacement in a traditional way.

In 1968, NSU launched the Ro 80, which would go on to win the European Car of the Year. Unfortunately, and usually about 50,000 kilometres later, most of them would go on to explode.

The issue was the rotor tips. In a normal piston engine you have piston rings, and these are seated to prevent the controlled explosion from becoming an uncontrolled one. In the Ro 80, the soft tips would eventually wear down allowing gasses to bleed out all over the place: more like an external combustion engine.

The solution was stronger material for the tips but the damage was mostly already done to NSU's reputation and finances. Compounding things, mechanics didn't really know how to service the Wankel and the engines were quite thirsty. Crippled, NSU was easy pickings for VW group, and there our story might have ended.

But it doesn't. Luckily for the not-quite-ready-for-primetime German engineering, along came Japanese ingenuity. Mazda wasn't the only company attempting to solve the Wankel's appetite for apex seals (heck, even Rolls-Royce had a go), but they were the most successful. Their rotary-engined sport coupe bowed just a few years after NSU's early attempts: the 1967 Cosmo.

If NSU fumbled the ball, you have to say that Mazda ran it in for a touchdown. They were able to meet '70s US air-quality regulations with a clever exhaust modification dubbed a "thermal reactor" (and really, which would you rather tell people have in your car - a catalytic converter or a thermal reactor?).

By the time the first RX-7 sports cars rolled around in 1978, Mazda had made the rotary a real alternative to the piston engine. It was quite reliable, compact and lightweight enough to allow for great handling - swapping rotary engines into early British roadsters is still popular.

Mazda also had enormous racing success with their rotary-powered cars. Most notably, they remain the only Pacific Rim manufacturer to win at the 24 hours of LeMans, and the RX-7 has won more International Motor Sports Association titles than any other car.

Racing success aside, the rotary engine still has its drawbacks. It's thirsty - a last-generation RX-8 gets about the same fuel economy as a V-8 Mustang. You have to top it up with oil, and it is possible to flood the engine - you need a careful owner and a knowledgeable mechanic.

The last rotary-engined cars sold on our shores left Mazda dealerships as a 2012 model of the RX-8. No 2013 model is available and there are no direct plans for anything in Mazda's pipeline.

Sad. I spent a little time last year with what I consider to be the pinnacle of the rotary engine, the 1993 Mazda RX-7 twin-turbo. It's a hero car for me, and I found it to be everything I hoped for and more.

When the last rotary engine rolled off the line in September of last year, it seemed like the end of an era. If Mazda can't make the Wankel work, nobody can.

But there are rumours out there. Whispers of Mazda's Skyactiv tech being applied to cut fuel consumption and add torque. Somewhere deep in Mazda's Hiroshima headquarters, they're working on it. I hope they get the rotary spinning again. I know they can.

Brendan McAleer is a freelance writer and automotive enthusiast. If you have a suggestion for a column, or would be interested in having your car club featured, please contact him at mcaleeronwheels@ gmail.com. Follow Brendan on Twitter: @brendan_mcaleer.

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