New York 2012: Five Minutes With Porsche's Cayenne Diesel Chief Powertrain Engineer

Stefan Fegg is the Project Manager for Powertrains on the Porsche Cayenne. Deputy Editor Joe DeMatio spoke to him while sitting in a Porsche Cayenne Diesel on the Porsche stand at Javits during media days for the 2012 New York Auto Show. The Cayenne Diesel goes on sale this fall for $55,750, versus $48,850 for the gasoline V-6 Cayenne.

What's the name of this thing, anyway?

Porsche Cayenne Diesel is the official market name.

Why a diesel-powered Cayenne when the VW Group already has Volkswagen Touareg and Audi Q7 diesel-powered SUVs?

Two reasons: 1) Because the number of diesel vehicles on the U.S. market is rising significantly. 2) The second reason is, why not? This car follows the company philosophy of best-in-class on-road performance while providing a reduction in fuel consumption. And with 28 mpg on the U.S. highway cycle and a 26.4-gallon fuel tank, it can go 740 miles without be refilled.

Why didn't you do one earlier, then?

We launched the Cayenne Diesel in Europe in 2010, with the Generation I engine. A lot of American media drove V-6 gasoline and V-6 diesel Cayennes back-to-back during the European press launch and told us: "The car is not noisy, it has great torque, it's good for the U.S. market.

Why don't you sell it in America?

We didn't reach U.S. emission standards at that time. We reworked the engine for its second generation: new cylinder heads, a new intake system, a reworked exhaust gas recirculation system that now allows us to bring back into the intake manifold about 60% of exhaust gases.

We reworked the turbo, and boost pressure is now 38 psi. New Piezo injectors provide six multiple injections per working cycle, for a better mixture.

How much heavier is the V-6 diesel than the gasoline V-6?

Gen I to Gen II, we lowered the weight of the engine by 55 pounds. It weighs about 20 kilograms (44 lb) more than the gasoline engine. We have a very fast diesel pre-flow system. This system heats to 1832 degrees Fahrenheit in 2 seconds.

Besides fuel economy, why might a Cayenne buyer want the Diesel rather than the V-6?

You can feel it in the acceleration. We're at 7.4 seconds 0-60 mph for gasoline, 7.2 seconds for the diesel. Top speed on the gasoline Cayenne is higher, 142 mph, because it has 300 hp versus 240 hp for the Diesel. The Diesel's top speed is 135 mph.

Any chassis or suspension differences between V-6 gasoline and V-6 Diesel?

The suspension tuning is adjusted to the higher weight of the car, but otherwise there are no differences.

How much heavier is the Diesel than the gasoline V-6, anyway?

The Diesel weighs 4795 lb. The V-6 gasoline is 4475 lb.

So, why should someone consider the Cayenne Diesel rather than the Audi Q7 diesel?

The performance on the Cayenne diesel is much better. We are best in class in weight. We do separate calibration of the engine and the transmission. Different shift points and times. We did learn a lot from Audi from the development of the base engine. They were the first ones with the diesel. But with the calibration, I think, we are one step beyond the Audis. Because we calibrate more for sportiness.

For more on the 2012 New York International Auto Show, including videos, the latest photos, and more information, click here to visit our New York Show homepage.

 

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