Gavin Green on the future of internal combustion engines

Published: 24 August 2016

► The future of combustion engines explored
► Rotaries, turbochargers and gas turbines
► Is there really life in the old petrol motor yet?

The internal combustion engine may be in the autumn of its long life. Fortunately, it looks like enjoying an Indian summer rather than a foggy fall. At the 2015 Tokyo motor show, Mazda previewed a shapely new concept car called the RX Vision, powered by that most delightfully simple of power units, a rotary. A production version for 2017 was hinted at.

Meanwhile, the sight of the delicious Jaguar C-X75 thundering through the streets of Rome in the Bond movie Spectre reminded me of the early days of that stillborn concept car, when it was powered by twin micro gas turbines. The good people at Bladon Jets continue developing their promising engines, and production versions are one day likely. 

But let us return to the rotary. The brainchild of former Hitler Youth leader Felix Wankel, the rotary has many advantages over a conventional petrol unit, including one-third the weight and size. As there are no reciprocating parts or a valvetrain, it is smoother and quieter. NSU, precursor of Audi, gave the world the first production rotary car, the two-seat Spider of 1964. Later came the Ro80, the most avant-garde sports saloon of the ’60s. In 1967, Mazda gave us the rotary-powered Cosmo, the first futuristic Japanese sports car. 

The Ro80 and Cosmo had much in common, including delectable looks. A smaller engine gives designers greater styling freedom, as well as the potential for better packaging. (And great packaging is the hallmark of superior car design.)

Alas, there were bugbears with the only fundamentally new car engine to emerge, with any success, in the 20th century. First, was reliability. This was a problem those clever Japanese at Mazda apparently solved, as evinced by its rotary-powered victory at Le Mans in 1991. The second problem was the rotary’s poor fuel economy, due to seal leakages and inferior thermal efficiency. That a lighter and smaller engine should be less economical was a cruel irony; eventually even those rotary stalwarts at Mazda abandoned their free-revving progeny.

Now, the rotary is on the verge of a comeback. Mazda and Audi, unsurprisingly, are leading the resurrection. Back in 2010, Audi showed one of its many electric concept cars, the A1 E-tron, which used a little single-rotor engine – less than 10in x 10in – as an on-board range-extending generator. The rotary may be a gas-guzzler as the primary power source, as revs rise and fall, and loads vary. But at constant and optimal rpm, such as experienced by a range-extending generator, it is ideal.

Mazda is coy about the precise mechanical make-up of the RX Vision, but the clear hint at Tokyo was that its rotary engine would be the primary power unit of a future production car, directly driving the wheels; thus Mazda may have solved the unit’s inherent thirst, probably through a mix of turbocharging, direct injection and laser ignition, replacing spark plugs.

Meanwhile, the best thing about the latest Bond film is the night-time car chase through Rome. This must be the first chase in movie history where the star cars (Aston Martin DB10 and Jaguar C-X75) cannot be purchased – well, not easily, at least. The villain drives the C-X75, that most felicitous of concept cars that first wowed us at the 2010 Paris show, disappeared (as concept cars do), was resurrected as a proposed limited-edition hybrid supercar, before being cancelled once again. In true 007 style, it only lived twice. 

Well, perhaps emulating Jaguar’s feline symbol, it may now be on its way to nine lives. In Spectre, the C-X75 returned from the grave, fitted with the F-type supercharged V8. The original C-X75, though, had one of the most innovative powertrains ever: four electric engines (one per wheel) whose batteries were charged by two Bladon micro gas turbines. As with all internal combustion units, these little engines are at their most fuel efficient when running at constant revs. On top of the plug-in facility, they provided jet-powered electricity. They’re also light, small and look exquisite. Bladon, part-owned by Tata, parent company of Jaguar Land Rover, continues its research. JLR boss Ralf Speth sits on Bladon’s management board.

So while the motor car’s future is undoubtedly electric, there will be a brief happy period when a range of novel internal combustion engines blossom, mostly as range extenders. Then – in 20 years? – like the horse before it, the oil-burning engine will be consigned to the scrapheap. Rotary and gas turbines may live on, though. Rotaries run superbly on hydrogen, while gas turbines are happy on a diet of biofuels, CNG or LPG.

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By Gavin Green

Contributor-in-chief, former editor, anti-weight campaigner, voice of experience

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