Porsche has thrown open the doors of its top-secret Weissach research and development centre to reveal the Porsche Cayenne Hybrid – a full two years before the car arrives in showrooms.Porsche’s new petrol-electric drivetrain system is known as a parallel hybrid and is being developed along with VW (for use in the Touareg) and Audi (for the Q7). Unlike the systems used by Lexus and Toyota, this parallel hybrid effectively slots into the vehicle’s existing drivetrain layout, rather than replacing it.The new car will use the base model’s standard-issue 3.6-litre direct injection V6 engine. The Hybrid Module is a made up of a 34Kw electric motor and a high-strength clutch mechanism, and is sandwiched between the engine’s flywheel and the automatic transmission.Porsche engineers have also added a nickel metal hydride battery in the spare wheel well, and a large power electronics module in the engine bay. This acts as a transformer and controls the highly complex switching mechanism, which allows the car to alternate between the petrol engine, electrical power and a combination of the two.
A Porsche that does 34 to the gallon
Porsche says that it is aiming for a real-world return of 34mpg with this car, along with the low levels of exhaust pollutants characteristic of petrol-electric hybrids. A V8-engined Hybrid is possible, but will not be produced, says Porsche.However, because the Cayenne is capable of starting and running on electric power only, engineers have had to re-think the vital ancillary parts. The oil pump, water pump, steering pump, air-con pump and brake servo assist are all now powered by electricity, allowing the Cayenne to function normally, even when the petrol engine isn’t running.To add to the complexity, an extra cooling circuit has been built in for both the power electronics module and the electric motor. The crash-protected battery pack is also air-cooled, using chilled air drawn from the passenger cabin.However, the Hybrid Cayenne doesn’t need either a starter motor or an alternator: the electric motor does both jobs. Porsche says that Cayenne’s functionality has not been affected: it can still tow 3.5 tonnes and can wade through 50cm of water. The 69kg battery will also kick into life at -30c.The production car will not arrive before late 2009 and the same hybrid transmission will also be available in the Porsche Panamera saloon in 2010. Porsche engineers, however, would not give any clues as to the likely price premium for the electro-Porsche.