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’ (although they’re not cylindrical) engine. Because the movement is always rotational, there’s no reciprocating motion, so it’s very smooth. And there are three complete combustion cycles per single engine revolution.
Previous Mazdas have had multiple rotors (the RX-8 had two, the Le Mans-winning 787B racer had four), each adding three chambers to the mix. Hence the 787B four-rotor (so 12-chamber, 12 full combustion cycles per revolution, twice as many as a V12) screamed like it was going to explode 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 would want it to drive the generator to which it’s bolted. Plus it’s nicely weird.
Anyway, this rather complex ICE sits transversely beneath the bonnet, as does the electric drive motor, which powers the front wheels.
The 50-litre fuel tank sits beneath the floor, along with the battery, which can take DC charge at a maximum of only around 36kW but, being little, gets filled up quite quickly.
The rotary engine makes 74bhp, but that doesn’t matter, because it never drives the wheels directly. The electric 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 kickdown stop). As a result, the 0-62mph time is 9.1sec, rather than 9.7sec for the 143bhp MX-30 EV.
If all this sounds complicated, don’t worry: 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.