2008 Volkswagen Jetta Clean Diesel

2008 Volkswagen Jetta Clean Diesel

I'm just clearing customs on my way home from Europe when my cell phone rings. It's Keith Price, our favorite Volkswagen product rep, calling. He's on his way to Ann Arbor in a 2004 Jetta, and he wants me to drive it. A 2004 Jetta? Keith is obviously up to no good, so I immediately agree to meet him.

He volunteers to rendezvous at my house, since I'm not going into the office, and I rush home. A few minutes after I get there, a blue Jetta pulls into my driveway and sits there, idling. I walk outside meet them - it's Keith and Norbert Krause, director of the Engineering and Environmental Office. They're both smiling.

A few seconds pass, and I realize they're smiling because I haven't figured out what's going on yet. I listen carefully, and I can just barely hear the faint clatter of a diesel. This particular car might be a few years old, but under the hood is something brand new: next year's 2.0-liter, sixteen-valve Clean Diesel.

The last Jetta TDI sold here was the 2006 model, which had a 1.9-liter four-cylinder with 100 hp that was rated at 30 mpg city, 38 highway. That's not bad mileage - and it was significantly better than the gas engines - but that diesel's technology is nearly ten years old.

Beginning early 2008, the Jetta will again be available with a diesel - a 2.0-liter unit that pumps out 140 horsepower and 235 lb-ft of torque - but this time, it comes with all new technology. (Incidentally, though it's the same displacement as the 2.0T FSI, the engines don't share any major components.)

The new engine's fuel injection system uses piezo injectors and operates at up to 1800 bar - that's a staggering 26,000 psi. The ultrahigh pressures help ensure that the diesel atomizes and combusts completely, maximizing power and minimizing pollution, smoke, and noise. Air is force-fed into the cylinders via a variable turbine geometry turbocharger that helps minimize turbo lag.

More importantly, the Clean Diesel is 50-state legal, meeting the ultra-strict BIN5 ULEV2 standards. It uses a selective catalytic reduction system that is maintenance-free for 120,000 miles, and no urea injection is needed. Despite the big bump in horsepower, the new engine produces a staggering 60 percent fewer emissions than the old 1.9-liter.

Mounted close to the engine is a single housing that contains an oxidation catalyst (to manage hydrocarbons and carbon monoxide) and a particulate trap (to reduce smoke and particulate emissions). Further down the exhaust stream is a Lean NOx trap that stores oxides of nitrogen, burning them off at regular intervals during driving.

That complex exhaust aftertreatment sops up most of the fuel economy benefit - about ten percent - that the new engine would otherwise provide. Still, engineers have seen fuel economy as high as 40 mpg in city driving and 60 mpg on the highway. EPA numbers haven't been released, but Volkswagen expects the ratings on the new, more difficult 2008 EPA test, to be about the same as the 1.9-liter's.

The Jetta Clean Diesel will come standard with a 6-speed manual transmission; the car in my driveway had the optional 6-speed, twin-clutch DSG.

Put anyone familiar with old-technology diesels behind the wheel of the new Clean Diesel, and they simply won't believe that the Jetta isn't gasoline-powered. Forget everything you think you know about four-cylinder diesels - driving with the windows up, there's no clatter to be heard, no vibrations to be felt, and there's certainly no smoke to be seen in the rear-view mirrors.

Hit the accelerator, and, unlike diesels of yore, the Jetta actually accelerates - quite quickly, in fact. While the base Jetta has a 2.5-liter five-cylinder gas engine has ten more horsepower, it has significantly less torque - and so the Clean Diesel is about as fast in a stoplight drag.

So what's the catch? The only one we can think of is the price. Figures haven't been announced yet, but we expect that the Clean Diesel will carry a small price premium over the base gasoline engine - maybe $1000 to $2000. Even at two grand, that's a much smaller premium than a hybrid system would cost. Furthermore, the Jetta won't need a new $10,000 battery in a few years' time, and its fuel economy isn't hyped up - it will be phenomenal in the real world.

Hey Keith, can we have a Four Seasons Jetta Clean Diesel test car, please?

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