Each chamber completes one combustion cycle – intake, squeeze, bang, exhaust – per turn. So with one rotor, as here, which has a combined 830cc capacity between the three chambers, you in essence have a small-capacity three ‘cylinder’ (though they’re not cylindrical) engine. Because the movement is always rotational, there’s no reciprocating motion, so it’s very smooth.
Previous Mazdas have had multiple rotors (the RX-8 had two, the 787B Le Mans winning racing car had four), each adding three chambers (like cylinders but not cylinders) to the mix. Hence the four-rotor (twelve-chamber) 787B screamed like a V12 and then some at 8500rpm.
Kota Matsue, the general manager of Mazda’s powertrain division, has had to explain to otherwise knowledgeable Mazda insiders – I gather to some disappointment – that this famous noise wouldn’t be accompanying a single-rotor generator that tends to run from 2300rpm to 4500rpm.
But, he says, the advantages are that it’s lighter and more compact and smoother than an equivalent four-stroke engine, and that the output shaft is in the middle of the block, which is where you’d want it to drive the generator it’s bolted to. Plus it’s nicely weird.
Anyway this rather complex unit all sits transversely beneath the bonnet, as does the drive motor, which powers the front wheels. The 50-litre fuel tank sits beneath the floor, along with the reduced battery, which can take DC charge at a maximum of around 36kW, but is only little so charges quite quickly.
The rotary engine makes 74bhp but that doesn’t matter because it never drives the wheels directly. The electric drive motor makes 168bhp, but the battery output can’t quite keep up with that, so in hybrid mode under hard acceleration the engine and generator pitch in to make up the difference (or even in EV mode, if you wilfully pass the throttle’s kick-down stop). As a result, the 0-62mph time is 9.1sec, rather than 9.7sec for the 143bhp pure BEV MX-30.
If all this sounds complicated, and I suppose it is, as a driver you don’t need to know it. You just set the drive mode and away you go, as an EV if you like on the daily commute, with the backup range for visiting gran at weekends. Shift paddles change the retardation level, and mostly it hums along electrically and smoothly with, under acceleration, the occasional distant mid-range whirr of a rotary engine being run at full load, sounding a bit like somebody running a masonry drill three-doors down.