Range-extending rotary opportunity for Mazda

Mazda is hard at work on a range-extending power unit that could be a cost-effective and efficient means of developing a plug-in hybrid from a battery/electric vehicle.

The internal-combustion engine is a single-rotor Wankel unit, and the technology would be licensed or sold to any manufacturer wanting to leverage Mazda's renowned subject-matter expertise in rotary-engine development.

Mazda's R&D chief, Kiyoshi Fujiwara, told Australian journalists visiting Japan for the Tokyo motor show last week that the manufacturer was developing the rotary range-extender as a bolt-in unit to suit any EV.

"The range extender unit is very small displacement, therefore that range-extender unit can be utilised for any EV – even another brand's EV. Some other companies are very interested in our range-extender unit..." he said.

President and CEO of Mazda, Masimichi Kogai, was also questioned about the rotary range extender. According to Kogai-san, development work on the range extender is continuing, and Mazda is not yet in a position to license the technology or offer it as an off-the-shelf solution for EV/plug-in manufacturers.

"We are not at that stage yet... the biggest area we need to work on is cost improvement. This is one rotor for the range extender, so we need to make improvement and then do some more work on combustion efficiency and also the cooling devices..." he explained through an interpreter. "To be able to mass-produce that... the cost needs to come down..."

Asked what was required to make it production-ready, Kogai-san indicated that the main problem facing the range-extender unit was currently the cost of re-engineering a conventional car or an EV to accommodate the unit.

"To reduce the cost we need to make it [the rotary] smaller and lighter," he said.

"We are going to place that under the trunk [boot] lid, but if we are to place a big range-extender unit under the trunk lid, we really need to have reinforcement everywhere – and that is going to add cost. And also we need to change the frame and the structure. That means we have to have two types of platform – one with range extender and one without range extender. That doubles the cost, because we have to have two.

"That means that we need to work on a compact and lightweight unit that can be mounted in any platform.

"By being able to do that we can deploy that across all car lines; that means we can gain volume, and then the unit cost will go down...

"[If] the hybrid system is something that you can just install in a conventional platform, or a platform with a conventional engine, that is why they can deploy that into a wide range of vehicles, without too much cost."

By being small enough and light enough – with easy installation in an EV and direct access to cooling air – the rotary range extender could yield a total range of 400km (with battery power included). To keep the rotary fuelled, the vehicle owner would have to fill a nine-litre tank integrated with the engine. Most of the time, the owner could keep the battery charged for shorter journeys and avoid the trip to the service station. But in the event of more time spent out on the road, the rotary would be available to get the vehicle owner to the next town.

There's no word on when the rotary range extender will be made available, but it will likely be among the first generation of new, small-displacement engines designed specifically for plug-in hybrid applications, unlike the engine in the first-generation Chevrolet Volt, which was sold here badged as a Holden.

Pictured: Mazda Demio (Mazda2) EV