VW's Volt: 2011 Volkswagen Golf TwinDrive

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Volkswagen is working on a plug-in hybrid version of the Golf/Rabbit, named Twin Drive, for introduction in 2011. A basic proof-of-concept version using a diesel engine is currently testing, in a 20-car fleet, in Berlin. But at the Golf 6 launch, VW engineers said the production version will be gasoline-powered because emission controls will soon get too expensive for a hybrid. The Golf Twin Drive's electric-only range is targeted at 30 miles.

Although VW engineers talk of the Twin Drive's gas engine as a range extender, the gasoline motor is clutched to the wheels. That's quite unlike GM's Volt, where the combustion engine never drives the wheels mechanically.

There is no conventional transmission in the Twin Drive, however, its absence helping to offset the weight of the electric motor. The single-gear ratio is equivalent to the top gear in a normal car. So the electric motor is needed to supply the low-end torque to get the car rolling to about 30 mph, when the combustion engine is clutched in and starts. The electric assist then rapidly fades, but is re-energized for acceleration boost.


There's 40 hp of regeneration braking. Reversing is electric-only. An "e-mode" button can be pressed in ZEV-only areas, which inhibits the gas engine completely.

The 350-lb battery pack is by Sanyo, with lithium-ion cells. Capacity is 12 KWh, though it is normally depleted only by 8 KWh. It is located in the trunk floor, so apart from an absence of spare tire this Rabbit has the same packaging as the base car.

The gas engine is a 1.4L turbo direct-injection four on experimental cars, but a production version would likely take a cylinder off that, producing a 1.05L triple of 100 hp, plus the electric boost when needed. This downsized-with-turbo concept gives high fuel efficiency and added flexibility to cope with the absence of intermediate gears.



The system controller is linked to the vehicle's navigation system, so it calculates when best to use up the available battery charge -- if the system knows an urban area is ahead, it will run longer on the gasoline engine. It will also ensure the car arrives at its destination with batteries depleted, ready to take on cheap electricity rather than expensive gasoline.

VW is setting up a partnership with German electric utility E.ON, which, according to the VW engineers, has spare night-power capacity to charge 10 million electric vehicles.