Testing Porsche's new 2010 Hybrid Cayenne prototype

Porsche Cayenne Hybrid
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Testing Porsche's new 2010 Hybrid Cayenne prototype

We're doing about 35mph, and the road suddenly turns straight and empty enough for Dr Michael Leiters to sink the Cayenne's accelerator. Not all the way to the floor but firmly enough to feel the Porsche surge forward in a smooth stream of unhesitating power.

Nothing remarkable about that, you may think, except that this Cayenne has switched from pure electric propulsion to a petrol-electric combination, and all without the slightest shudder, tremor or shake. What happened, when Porsche development engineer Leiters accelerated, was complex and perfectly synchronised. The electric motor continued spinning, and was joined in an instant by a petrol engine that had previously been turned off. An electronically controlled clutch, operating with incredible precision, allowed one engine to spin up to the speed of the other without causing clunks or jerks. Admittedly this is a Porsche engineer driving this car rather than your reporter, but we go far enough and hard enough to make it pretty unlikely that he is covering things up.
That straight piece of road lies just outside South Africa's Johannesburg, where we're on-board a prototype of the all-new 2010 Cayenne four-wheel drive. I'm witnessing the last stages of shakedown testing of this car, one of just four reporters worldwide to ride in the Cayenne months before it goes on sale here in June.

Don't go thinking that this hybrid Porsche lacks bite, though. The petrol and electric engines fire out 380bhp combined and a fat 428lb ft from 3000rpm, enough to get this Cayenne to 62 mph in 6.5sec. That's with both the 333bhp 3.0 supercharged Audi V6 and the 46bhp electric motor working flat-out, although this hybrid operates with either engine individually. It can drive at speeds of as much as 40mph in electric drive alone - a Toyota Prius manages 31mph – though only for a distance of 1.6 miles. Like every other hybrid, the main benefit of the electric motor and battery pack is to take advantage of the energy wasted when the car is braking - the brakes are used to charge the battery, which assists the petrol engine, enabling it to use less fuel.

But a major difference with this Porsche is that there is no recharging when you simply release the accelerator, the car coasting instead, free of engine braking, at speeds of up to 98mph. So if you drive with good anticipation, you can frequently cover big chunks of ground simply by coasting - it's like freewheeling with a bicycle. The upshot is a 20percent fuel saving compared to a V8, a combined consumption of 34.5mpg and CO2 emissions of 193g/km – vastly better than the 244g/km of the outgoing Cayenne diesel.

Despite its eco-aspirations this hybrid Cayenne is designed to be as dynamic as the rest of the range, as proved by the provision of a sport mode. It sharpens the accelerator's response, lowers the ride height and provides extra boost from the electric motor when more than 70 percent of the throttle is used - normally it only activates in kickdown. There's also an E-Drive mode, which maximises the use of the electric motor to save fuel. But whatever mode it's in, this hybrid appears to drive with the seamless ease of the Turbo S we also try.

That's how this hybrid Cayenne goes, but what's the rest of this all-new, second generation version of Porsche's biggest like? At first sight it looks smaller, and it is lower, but it's actually longer, wider and designed to look more like Porsche's 911. That's why the rear pillar is more raked, why its nose plunges and why the wings bulge muscularly around their wheels. There's more room inside an interior finished to much higher standards, and an impressive array of centre console buttons that allow major systems to be operated without using a confusing menu system.

But the most important change can't be seen, and that's the reduction in the Cayenne's weight. Deleting the off-roading low ratio gearbox (eight speeds and more sophisticated Porsche Active Suspension Management compensate, says the company) and using aluminium for the car's axles, bonnet, doors and front wings all contribute to a weight saving of around 180kg. That benefits performance, economy and agility, and it's clear from the passenger seat that this big car corners confidently and with remarkably little roll. The ride is decent enough in the hybrid too, which rides on 19in wheels, but it's less impressive aboard a 21-inch alloy-equipped Turbo. There's no doubting the Turbo's go, though, and it makes some good noises doing it, too.

From where we sat this 2010 Cayenne looks like a solid all-round improvement, while the hybrid version provides an intriguing way to make this performance SUV usefully more acceptable to both your wallet and your conscience.
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