Rotary engine returns with electric Mazda2 prototype
One-off electric vehicle has small gas engine to extend its range
The rotary engine is back.
Actually, it’s quite literally 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-hp electric engine.
The range-extending package grafted onto the prototype is nearly completely self-contained, consisting of a flat-mounted singlerotor 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 whirr of the rotary range extender kicking in and spinning to 4,500 rpm make for an interesting experience, if not quite a production-ready one.
The 330-cc 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 addon 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.