Mitsubishi MiEV II Prototype 2011 Review

Range-extended hybrids look likely to be the next step towards a fully electrified vehicle fleet. Mitsubishi is looking to fast-track this type of vehicle with a production softroader not too far distant.

Chevrolet's Volt can, it seems, take credit for turning petrol-electric technology on its head. It's prompted at least one form of flattery from a rival – with others likely not far behind.

The American-designed and engineered Volt reversed Toyota’s top-selling hybrid system by using petrol power to create electricity on the move, and using only an electric motor to directly drive the wheels.

Now Mitsubishi is developing a plug-in hybrid system strikingly similar to that of the Volt: it too uses a petrol engine to charge the onboard battery pack to extend driving range.

Its latest concept can travel about 50km before the petrol engine kicks in and acts as a generator to recharge the battery pack. This gives an estimated driving range of more than 800km in its current configuration, says Mitsubishi. (For the record, the Volt – which goes on sale in Australia next year -- can travel about 64km before the petrol engine acts as a generator, providing a total driving range of about 400km.)

The Mitsubishi system goes a few steps further than the Volt’s: it has two electric motors, one for the front and another for the rear wheels which can be used independently or at the same time for all-wheel-drive traction.

Its final trick: at freeway speeds (in the case of the prototype, above 120km/h) the petrol engine can directly drive the front wheels via a transaxle with a ratio similar to sixth gear in a conventional car… The Volt has one electric motor, and the petrol engine never directly drives the wheels.

The Mitsubishi system was shown in updated form at this year’s Tokyo Motor Show – two years after the initial concept was revealed. For the first time, however, journalists were allowed to test drive a prototype of the system at Mitsubishi’s Okazaki test track.

Although still two years away from production, the hand-built system felt more refined and more capable than the Volt which has been on sale in North America for a year and due in Australia late 2012.

The PX MiEV II is predominantly an electric car and at suburban speeds the petrol motor only kicks in to boost the battery pack if you floor the throttle, just as it does in the Volt.

A display shows that the front electric motor does most of the work most of the time, but the rear electric motor also gives acceleration a gentle boost.

That explains why the PX MiEV II feels quick – and refined. Mitsubishi staff warned us that the vehicles were fragile working prototypes and not to be driven hard. But the system felt more polished than the Volt, at least compared to the production cars I have previously driven.

Acceleration from rest was more brisk than a petrol-powered Outlander – and smoother and quieter.

On the high-speed track the transition from pure electric to petrol power was seamless. There was no driveline clunk; the only way you could distinguish the switch in power was the noise of the petrol engine as the speed climbed to 120km/h.

That’s the speed at which the petrol engine begins to directly drive the front wheels in the sample cars. This could be changed on production cars to a lower speed, such as 80km/h, but Mitsubishi says it depends on the vehicle and individual market needs.

Mitsubishi's product manager for the PXII MiEV, Mitsuyoshi Hattori, says the concept vehicle is an “electric car first”, with the 2.0-litre petrol engine intended to increase driving range – and enable extended freeway driving ability.

He said that if the car were to driven on electric power above 100km/h for extended periods, the petrol engine wouldn’t be able to recharge the battery pack quick enough.

The idea to use a petrol engine as a generator for a hybrid system was dreamt up by a 30-year veteran of General Motors, engineer Jon Lauckner. He initially sketched the layout on a scrap of paper during an impromptu meeting with GM’s then product chief Bob Lutz in January 2006.

One year later they unveiled the Volt concept car, at the 2007 Detroit motor show, with a presentation that gave the impression GM had been working on the system for decades.

By the time it reached production, the Volt would use a 63kW 1.4-litre petrol engine (max 4800rpm) to power a 55kW generator that, in turn, recharges the onboard battery pack.

It’s the antithesis of the technology Toyota had developed for its Prius, the world’s top-selling hybrid car. The regular Prius can be driven about 1km on battery power alone in ideal conditions and recharges its battery pack via regenerative braking.

A plug-in Prius under development can travel about 20km on battery power before the petrol engine takes over. Toyota is expected to launch a plug-in hybrid version of the Prius for public sale in the coming years. However, Toyota is yet to reveal if it will adopt a Volt-style hybrid system in future, for even greater petrol-free driving range.

Other carmakers have been studying the Volt since it became available for the public to buy a year ago, and are expected to introduce similar systems. It now seems likely that Mitsubishi will be the first…

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