First Drive: 2008 Volkswagen Jetta TDI

Volkswagen’s 50-state-compliant Jetta TDI will be among the cleanest diesels in the U.S.

Previews

Amid the looming hordes of European luxury automakers planning a North American compression-ignition invasion in the next couple years, humble Volkswagen has announced its plans to return the Jetta TDI to the diesel dogpile in the spring of 2008. Powered by a new 2.0-liter four-cylinder making 140 hp and 236 lb-ft of torque, and either a six-speed manual or DSG automated manual transmission, the 2008 Jetta TDI will be cleared for sale in all fifty states.

Some of the earlier diesels to make it to our shores over the next few years will only be available in 45 states; California, Maine, Massachusetts, New York, and Vermont have all adopted stricter emissions regulations for diesels that bar some vehicles from entry. Using technology developed under the BlueTec cooperative formed by Mercedes-Benz and Volkswagen, the Jetta TDI will slip by these stricter regulations without resorting to a urea-based exhaust treatment, as many BlueTec labeled models will.

Nitrogen oxides (NOx) are, along with particulate emissions (soot), the biggest hurdles facing diesels in the U.S. Most BlueTec vehicles will control NOx by injecting a urea-based solution called AdBlue into the exhaust system upstream of a catalytic converter that specifically targets NOx. In that catalytic converter, the ammonia in the urea reacts with the NOx in the exhaust gas and neutralizes it into nitrogen and water.

Volkswagen’s Jetta TDI will manage without a urea injection system by using a NOx-storage catalyst. Like the particulate filters in place on this car as well as other diesels, this catalyst is basically a trap that temporarily holds the offensive emissions. Periodically, the engine will switch to a richer air-fuel mixture that will create a hotter exhaust gas and burn off the material in the traps.

From the driver’s seat, this rich-burn cycle is imperceptible. We had a chance to drive a near-production Jetta TDI and were pleasantly reassured by the transparency of not just the BlueTec technology keeping the car clean, but the diesel engine overall. Horsepower in this new 2.0-liter common-rail diesel engine is up 40% over the previous 1.9-liter four-cylinder, with torque up 33%. Those figures mean an increase in drivability of about 500%. With the previous engine, the best performance we managed to coax from a Jetta TDI was a sluggish 10.3 second 0-60 wheez. The additional power and torque produced by this new, cleaner engine bring that number down to somewhere in the low- to mid-eight second range. Under less aggressive feet, the TDI’s prodigious torque effortlessly whisks the Jetta away from stops and around traffic.

More Driving Impressions

Along with particulate and NOx emissions, BlueTec is rapidly abolishing that characteristic cylinder-full-of-pebbles diesel clatter as well. At idle, the driver has to be paying very close attention to notice that the engine underhood is popping diesel fuel rather than gasoline. Under acceleration, the exhaust sound is a little deeper and boomier than a gasoline Jetta, but not too noticeable to the average sorority member, a demographic that hoards transporter-loads of Jettas here in Ann Arbor. If they’re not used to running a gasoline engine up to redline (truncated in the diesel at just 4500 rpm), the only thing the Tri Delts will notice while driving the TDI is the inordinate number of leering stares they get at the diesel pumps.

Despite the BlueTec partnership, Volkswagen will refrain from using the BlueTec name on the Jetta TDI. Early information suggests that consumers associate BlueTec with Mercedes-Benz and incorrectly assume that a Volkswagen with a BlueTec badge is powered by a Mercedes engine.

Incidentally, to celebrate thirty years of selling diesels in the U.S. Volkswagen is searching for both the oldest and the highest-mileage diesel VWs still running their original engines. If you think your car could be a contender for one (or both) honors, go to www.vw.com starting March 1 to enter your car. VW is expecting at least one to be a 1977 Rabbit diesel. We know a guy who ran one at the 24 Hours of LeMons in October…

BY JARED GALL
www.caranddriver.com