Porsche's Green Peppers: Diesel and Hybrid Cayenne Models Spice Things Up

Porsche's Green Peppers: Diesel and Hybrid Cayenne Models Spice Things Up

By John O'Dell August 28, 2009

Porsche promises V8 performance and 4-cylinder fuel economy with 2011 Porsche Cayenne S Hybrid. 

By John O'Dell, Senior Editor

Hmm.  A Porsche Cayenne hybrid, or the diesel?

Spend $70,000 or so for a superpowerful, hybrid gas-sipper (27 mpg versus 18 mpg for the V6-equipped standard Cayenne), or around $52,000 for a powerful  diesel that delivers about 24 mpg? (The price tags are our best guesses. Porsche hasn't said anything official.)

Diesel? Or Hybrid?

Oops, the diesel isn't a choice, yet. You can only get it in Europe, South Africa and Australia right now - although Porsche is trying to find out if enough U.S. buyers would want one to make a business case for jacking up the emissions treatment system to meet U.S. standards and sending a few over.

The hybrid, however, goes on sale here in the spring, just in time to satisfy the green fancies of those who (a) have the bucks and (b) want to one-up the other Cayenne owners at the country club.

We got a chance this afternoon to take both new SUVs - a preproduction prototype Cayenne S hybrid and a European-spec Cayenne diesel - for a short spin in the hills of Beverly and were mightily impressed by both.

Diesel?  Hybrid?

It wasn't that long ago that most everyone in the automotive media was raising eyebrows and questions about Porsche's decision to build an SUV.

The conventional wisdom was that the gang from Weissach was about to ruin the image of one of the world's great performance car brands.

That was then, and since then, Porsche has sold more than 250,000 Cayennes, making the big SUV the best-selling Porsche model ever. Critics generally love it, and have praised Porsche for doing the un-doable and making an SUV that fits right in with the rest of the Porsche stable.

Until earlier this year the lineup consisted of the base V6 Cayenne, the V8 Cayenne S  and GTS, and the twin-turbo V8 Cayenne Turbo and Turbo S models.

As power and equipment levels rose, so did fuel consumption, with the Turbo models delivering a scant 14 mpg for the combined city and highway cycles.

To help answer critics who loved the Cayenne but hated its thirst, Porsche earlier this year introduced -in Europe, South Africa and Australia only -the Cayenne diesel, which since then has accounted for 60 percent of Cayenne sales, said Michael Leiters, who heads the Cayenne development program.

As it was developing the diesel, Porsche also put Leiters' team to work on a hybrid, figuring that in the U.S. at least, the market for hybrid luxury SUVs might be a lot stronger than that for diesels (and sales figures for BWM's diesel X5 tend to support that argument).

The Porsche system is modular, which means it can pretty easily be scaled up or down and fitted into other models - like the just-introduced 4-door Panamera. Everyone at Porsche is being coy about it, but we can't help but remember that the company said back in January 2008 that it someday would have a hybrid Panamera .

All Leiters would say today is that, if it happens,  it will be after the Cayenne hybrid launches next spring - same thing they were saying 19 months ago.

Hybrid?

Edmunds Inside Line presented a thorough first drive review of the Cayenne S Hybrid back in March, and  I can't really add anything to it: It's a tremendously well-engineered and well-thought out system that does a few things you'd never expect in a large SUV package.

Driving it around Beverly Hills didn't let the system pull out all the stops, but places like Beverly Hills are likely where most Cayenne S Hybrids are going to be driven, so Porsche was at least being realistic in its choice of venues.

 

Chassis ilustration shows layout of Porsche's linear hybrid powerterain.Click to enlarge.

 

With or without a hybrid system, the Cayenne is one of the nicer SUVs to drive, and the hybrid system lets you do some of it - about 2 miles at speeds under 32 mph and with a very light foot on the throttle - in all-electric mode.

If you manage to get out on the highway, the Porsche hybrid system - which functions like a more powerful, and smarter, version of Honda's Integrated Motor Assist (IMA) system - has a unique "sailing" feature.

The engine decouples from the drivetrain and, at speeds of less than 86 mph, you can lift your throttle foot and actually freewheel down the road with no engine drag whatsoever.  A great way to save a few pints 'o petrol here and there.

Speaking of petrol, Porsche says the Cayenne S Hybrid, with its 26-gallon tank and 27 mpg estimated fuel economy, will deliver up to 680 miles on a single load of fuel.

The 3.0-liter supercharged V6 - adapted from the Audi S4 - delivers 333 horsepower and, when the electric motor adds its grunt (which it doesn't do except briefly to help with acceleration), system output jumps to 374 horsepower.

Those horses turns the wheels via Porsche's first 8-speed automatic and, with all the damping and fine-tuning that Porsche's formidable engineering crew could bring to bear, the whole thing is as seamless, quiet and responsive as you'd better well demand from a car that is likely to cost what this one will.

The electric drive side of the system features a 38 kilowatt electric motor and a 288-volt, nickel-metal hydride battery (it's designed for power, not distance; had Porsche been looking for sustained periods of all-electric drive, it would have used lithium-ion chemistry).

Porsche says the Cayenne S Hybrid will deliver the performance of the V8 model with 4-cylinder fuel economy.

We can't verity the fuel economy from our short drive, but we did put our foot to the floor and can attest that Porsche's 0-60 acceleration claim for the hybrid - 6.5 seconds - is pretty spot-on.

For the tecchies, here's a boil down of the system, front to back: Supercharged V8, disengaging clutch, electric motor, torque converter, transmission, with battery pack installed under the cargo compartment floor in the rear of the vehicle. A sophisticated power control package sits beside the gas engine and conducts the orchestra.  

Unlike the Toyota system, which enables the electric motor to join the gas engine at almost any time, Porsche's linear system is almost always either running all electric or all ICE, said Leiters. The electric motor can briefly augment the engine when a burst of acceleration is demanded, but the drain on the battery is too much to let the two run in tandem for much longer than a slow wink.

Diesel?

You can get some of what the hybrid offers - improved mileage, and decent low-end acceleration - for a lot less money in the Cayenne diesel (right), if Porsche decides to bring it over.

As with the hybrid, Inside Line took the Cayenne diesel for a spin earlier this year and we encourage you to read the First Drive review for a detailed rundown of the car.

And/or you can check out Green Car Advisor's piece on the European introduction, for a look at the powertrain and fuel economy specs.

What we can add after a quick drive this afternoon is that it is a  refined piece of work, with virtually  no diesel clatter (you can catch a tiny bit at idle if you turn off the AC and stereo and strain your ears), no diesel odors, thanks to our new clean diesel fuel and Porsche's European-standards emissions treatment - and plenty of power, although not the remarkable output of the hybrid: It takes the diesel Cayenne 8.5 seconds to hit 60 from a standing stop, almost two seconds slower than the hybrid.

Porsche figures the diesel for about 24 mpg (U.S.) - a 28 percent improvement over the V6 gasoline model - with a cruising range of 600 miles thanks to the 26 gallon tank.

In Europe it makes tons of sense because diesel is much cheaper than gasoline, taxes on diesels are lower than on gas models  in many countries and, with all that diesel torque - 406 lb-ft of it - it offers the driving fun that Europeans demand.

In the U.S., of course, diesel isn't cheaper than gasoline and for a big part of last year it was more expensive; there are only modest tax breaks for driving a new clean diesel; there's no diesel history so it is an unknown technology for many; diesel fuel isn't as readily available as gasoline and diesel for many still means noisy and smelly - despite the fact that the new clean diesels and clean diesel fuel, along with engine noise damping technologies, have eliminated both clatter and odor.

So, hybrid? Or diesel?

If we had the choice, we'd take the diesel and save $15,000 or so.

But first Porsche has got to believe there's a market here. 

So let 'em know how you feel.

John O'Dell:  is an AutoObserver Senior Editor. Follow @AutoObserver on Twitter.