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Mazda joins rotary club

Prototype crams in single-rotor engine to extend EV's range

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The Mazda2 EV hybrid prototype marks a return to the rotary engine.

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The Mazda2 EV hybrid prototype marks a return to the rotary engine.

The rotary engine is back.

Actually, it's in the back, crammed beneath the trunk of this Mazda2, where it's making a whopping 30 horsepower and emitting the pew-pew-pew soundtrack of George Jetson's grocery-getter. Well, whatever it's doing, it's nice to see you again, you funny little triangle motor.

This prototype is a one-off all-electric version of the Mazda Demio, known in our market as the smiley-faced Mazda2. Mazda sells a plug-in variant as a fleet car in the Japanese home market; it introduced its EV in 2011 and it moved a modest 100 vehicles last year, mostly to government agencies.

This one, however, is a bit special. The ordinary Demio EV has a range of about 200 kilometres and it takes about eight hours to charge its Panasonic-sourced lithium-ion battery. Mazda was able to cram its battery pack underneath the framework of the ordinary gasoline-engine car without impinging on passenger space, with the removal of the fuel tank and installation of a 100-horsepower electric engine.

The range-extending package grafted onto the prototype is nearly completely self-contained, consisting of a flat-mounted single-rotor engine, nine-litre fuel tank, belt-driven transmission and generator. It's about the size of a tuba and it slots right underneath the Mazda2's rear trunk space without compromising cargo-carrying capacity, though the spare tire gets evicted.

Like most electric cars, the little Demio scampers off the line in a wave of instant-on electric torque, easily making it up to the 60 km/h speed cap enforced by a rather serious-looking engineer armed with a clipboard.

Mounted right where the infotainment screen would go is a Looney Tunes-style bright red kill switch with an all-caps EMERGENCY script brightly displayed above it. This prototype is essentially priceless, and clearly the Mazda R & D team came prepared for auto-writer testing methods.

It's a short test, just two laps of a glorified parking lot, but the cheerful whir of the rotary range-extender kicking in and spinning to 4,500 r.p.m. make for an interesting experience, if not quite a production-ready one. The 330-cubic-centimetre single rotor -- essentially a thinner, scaled-down version of half an RX-8 engine -- is compact enough to have Mazda considering installing it in a multi-fuel portable emergency generator. The 100-kilogram extender package essentially doubles the range of the Demio EV and could be sold as an add-on enhancement if and when Mazda starts manufacturing electric vehicles in serious quantities.

In the meantime, the company's focus remains firmly on chasing the maximum efficiency levels of the standard combustion engine.

Speaking of next-generation advances for Mazda's Skyactiv technology, Mitsuo Hitomi, in charge of powertrain development, casually dropped a further bombshell: Mazda intends to take its already high compression ratios into the scarcely credible 16-18:1 range, and it also intends to run its gasoline-engine cars without spark plugs part of the time.

In a diesel-engine car, very high compression -- the ratio by which the fuel-air mixture is squeezed -- results in spontaneous ignition; no spark is needed. In low and mid-load applications, Mazda has figured out how to control combustion and get usable power by using the same cycle for regular gasoline; rev the engine up to pass or climb a hill and it'll turn back to a normal spark-ignited burn.

Be gentle on the pedal, so goes the theory, and the ultra-lean operating conditions mean less gasoline used per piston stroke. Such benefits to flexible fuel economy mean Mazda theoretically won't need to spend precious development dollars on CVTs or eight-speed gearboxes and should be able to use lighter-duty hybrid systems that engage less often and therefore need less battery weight.

It might all sound straightforward, but it's something the rest of the industry has had difficulty with; Mazda doesn't expect its next-gen technology to be ready for prime time for something like half a decade. In the meantime, a stopgap is needed.

For the Japanese home market only, here it is: a hybridized version of the Axela/Mazda3. Licensing Toyota's hybrid technology and bolting it to a 2.0L Skyactiv engine on a sub-line in their assembly plant, Mazda then straps the powertrain into an ordinary Mazda3 sedan, offering the vehicle in one of three trim levels.

It's quite an odd car to drive. On one hand, the current Mazda3's driver-centric steering and handling dynamics are mostly retained, and much effort has been made to make the regenerative brakes progressive and more like an ordinary car. On the other hand, the shifter is the same as in a Prius, there's a CVT transmission and the power output is down to 134 hp in the name of fuel economy. It's a bit like getting a scoop of granola atop your cheeseburger.

Still, in the heavy stop-and-go of Japanese traffic, the tester managed to spend a full third of its time in electric-drive mode. Detuned though it may be, the grunt of the larger Mazda engine means better acceleration than any Prius, though there's a loss of the crispness you get from the well-programmed conventional six-speed automatic in the standard car.

In Japan, the current take-rate for diesel powertrains in Mazda's CX-5 and Atenza (Mazda6) is in the 70 per cent range, and the new hybrid may marginalize gasoline engines even further. North America shouldn't expect to see a hybrid any time soon, but given Mazda's streamlined manufacturing-line processes, it wouldn't be difficult to build a hybrid for Canada. It's just challenging to make the case for one.

The case for a usable small electric vehicle with an available compact range-extender? That's something else entirely. It might not be the reborn RX-7 you were waiting for, but while we wait, it's nice to know a new Mazda rotary engine spins once again.

-- Postmedia Network Inc. 2014

Republished from the Winnipeg Free Press print edition March 14, 2014 F2

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