Five years ago this month, Mazda’s then North American chief Masahiro Moro confirmed what researchers had known for some time: the company’s rotary engine would be ideal as an on-board motor-generator for battery-electric (BEV) vehicles.
“This is a very suitable engine to run a generator because it’s compact and lightweight, with no noise or vibration, and it has very good fuel economy,” he said in January 2018. “We have a lot of opportunity for the rotary engine.”
That opportunity has found its way into a new mainstream model, the MX-30 e-Skyactiv R-EV, unveiled at the Brussels motor show. But don’t expect it in New Zealand any time soon. The UK market gets first dibs on it later this year.
The MX-30 e-Skyactiv R-EV is an MX-30 EV compact in all but name and drivetrain. Like the all-electric MX-30 – launched in NZ in April, 2021 – it uses a lithium-ion battery pack. But e-Skyactiv R-EV gets something extra, something that motoring gods would smile on: a petrol engine.
It’s a 830cc Wankel rotary, generating 55kW/116Nm and fed from a 50-litre fuel tank. It serves only as a generator, charging a 17.8kWh battery that powers an electric motor that drives the car’s front wheels. In effect, the rotary turns petrol into electricity. Total output for the e-Skyactiv R-EV is 125kW/260Nm. Top speed is 140km/h.
The whole kit and caboodle operates as a series hybrid rather than a parallel hybrid, meaning it serves as a range extender, springing into life to charge the battery to push the vehicle’s range out to potentially around 600km, a significant increase over the 200km or so provided by the 35.5kWh battery in the MX-30 EV.
Fully charged as a PHEV – either at home from a wallbox or elsewhere from a fast charger – e-Skyactiv R-EV can run on electricity alone for around 80km. Claimed overall exhaust emissions are 21gr/km.
The rotary engine itself is different from the Renesis unit that powered the discontinued Mazda RX-8. For starters, it’s around 15kg lighter, has a higher compression ratio of 11:9.1, and features direct injection rather than Renesis’ port injection, an engineering change along with exhaust gas recirculation which improves economy by a claimed 25%.
Economy was still the “number one challenge with rotary”, Yoshiaki Noguchi, assistant manager of Mazda’s powertrain development division, told reporters at Brussels. “The combustion chamber is constantly changing with rotary, and to make the mixture right is very difficult. We have improved this and as a result we can improve fuel consumption.”
On the move, the rotary will kick in if more power is needed than the level of charge in the battery can deliver to the electric motor. A typical example is when flooring the throttle.
The e-Skyactiv R-EV has three drive modes. Normal keeps you going as long as the battery has enough juice to feed the electric motor; EV is electric-only power; Charge fires up the rotary to charge the battery.
There’s another creature comfort about the e-Skyactiv R-EV: the drivetrain can supply up to 1500 watts of power to electrical devices, or car to load (C2L).