(Sept. 18, 2008) SANTA MONICA, CA - Air quality problems in southern California have been the driving force behind automotive emissions standards for nearly four decades. With the newest rules particularly tough on diesel engines, it's fitting Santa Monica was the location for first drive of the first new car to meet those strict standards.

Volkswagen brought both a fleet of 2009 Jetta TDIs and journalists to drive them to the birth place of modern emissions requirements.

Volkswagen has long burnished a reputation for making cars that are both fun to drive and economical, and the Jetta TDI tailor made perpetuate the rep. While hybrid cars like the Toyota Prius and Honda Civic hybrid are both known their thriftiness, neither is generally considered particularly sporting thanks to limited torque, low grip and low rolling resistance tires. One of Volkswagen's goals with the Jetta was meet the hybrids head on in efficiency without sucking the joy out of the driving experience.

To do it, VW first had to pass the latest iteration of those emissions rules known as Tier 2 Bin 5 (T2B5). And unlike standards in other countries, the US rules apply to all engine types equally - regardless of what fuel they run on. That means that while the inherently more efficient diesel engine does well on the as yet unregulated carbon dioxide emissions, output of particulate matter (PM) and nitrogen oxides (NOx) are a whole different story.

 

NOx emissions are a particularly pesky problem because of the contribution to smog formation one of the main problems in the Los Angeles basin. As a result, California has set NOx emissions limits that are about one-fifth of those in the latest EURO-V regulation. This has been the biggest technical issue carmakers have had to tackle to pass muster in California.

Until relatively recently, diesel engines had a well deserved reputation for being noisy, smelly and spewing black smoke from the tail pipe. Anyone who has been stuck behind a diesel bus or garbage truck is familiar with this phenomenon. Manufacturers like Volkswagen, Mercedes-Benz and BMW along with suppliers like Bosch and Delphi have worked diligently in recent years to address these problems while also meeting the new emissions requirements. A number of technologies have emerged over the past decade that have incrementally met all those requirements while also improving performance and efficiency.

The first of these to appear was modern common-rail fuel injection systems, followed by diesel particulate filters. The most recent development was after-treatment systems to reduce the NOx emissions. The new Jetta TDI uses all of these elements to meet T2B5, beginning with the high pressure fuel system. The common rail injectors are able to provide up to seven distinct fuel pulses per ignition cycle.  With the extremely precise metering available, the fuel can be added progressively during the course of the power stroke allowing a more controlled burn. This helps to drastically reduce the knocking usually associated with diesel by eliminating the single large explosion with a series of smaller explosions.

This controlled burn process also helps cut down the average temperature of combustion, which is critical to minimizing the production of NOx. Nitrogen oxides are only produced when the combustion temperature get too high. Even with all this fuel delivery magic, some particulates and NOx still manage to escape out the exhaust pipe. That's where a particulate filter, which eliminates more than 90 percent of the soot earns its keep. The NOx emissions are lowered below the T2B5 limits with a lean NOx trap, which requires no maintenance unlike the urea injection systems that will be required on larger diesel engines.

The TDI driving experience 

Volkswagen provided the gathered media with a fleet of two dozen identical Jetta TDI sedans with the only variable being the transmission. Five cars had a 6-speed manual gearbox while the rest had Volkswagen's 6-speed DSG dual clutch transmission. The DSG uses a pair of clutches, one connected to gears 1,3 and 5 with the other engaging 2,4 and 6.

The clutches automatically engage/disengage alternately as the corresponding gears are engaged providing faster and smoother gear changes than either a conventional automatic or manual transmission. The DSG also has an efficiency advantage over a conventional automatic since the torque converter is eliminated.

Volkswagen invited reporters on an informal mileage marathon, seeking the best mileage over the 125-mile drive route. Since Volkswagen is intent on showing the Jetta doesn't sacrifice any of the Fahrvergnügen (driving enjoyment) that its cars are known for, the route beginning in Santa Monica California consisted primarily of driving up down a variety of winding canyon roads through Malibu and Ventura county intermixed with some more relaxed stretches along the Pacific Coast Highway.

The DSG was first introduced several years ago some drivers complained that the initial clutch engagement from a stand still was often rough and jerky. Setting out in a blue sedan equipped with DSG, no such complaint could be made about this Jetta as every launch was as smooth as the best torque converter automatics. The gear shifts were also among the smoothest I've encountered and were notable for the fact that they were imperceptible.

Anyone who doesn't like to shift for themselves should have no issues with the DSG.  The DSG also offers a manual shift option that can be activating by tapping the shift lever to the right from the D position and then tapping forward for an up-shift or back to drop down through the gears. Even in manual mode, the shifts were quick and smooth. Unlike other VW DSG applications, such as the R32, the Jetta doesn't offer steering-wheel mounted paddle shifters, so most drivers are likely to just let the gear box do the work.

Like most diesels, from a standing start, the Jetta doesn't jump off the line. But once underway, the ample 236 lb-ft of torque provides plenty of grunt at any speed for merging from freeway ramps or passing on a two-lane road. A Jetta TDI driver will likely never feel deprived of power at their command. That torque is also available in a remarkably civilized fashion. Drivers who haven't driven a diesel before and climb into the Jetta for the first time will likely never realize they are driving a diesel. This compact and relatively inexpensive sedan is quieter than many luxury cars costing $10,000 more.

The low sound levels are a perfect compliment to the driver's working environment. Volkswagen has long had a reputation for high-quality materials in its interiors and this car is no exception. The controls are well laid out and feel good to the touch. All the visible surfaces are finished in a soft touch plastic and there are no rough, unfinished edges anywhere. The seats, in typical German fashion offer excellent lateral support and are comfortable even after several hours in the car. 

Given the dynamic capabilities of the Jetta, good seats are important. The Golf/Jetta/Rabbit family of cars have always been nimble handling machines and the canyons of Malibu seem to be their natural habitat. From 2009, all Volkswagens are equipped with electronic stability control as standard equipment. Combined with a nicely balanced and tuned suspension, the Jetta driver can easily access all of the available grip without getting into trouble.

The Jetta has very mild understeer, and the steering effort is a bit light just off center. But as approaching the limits of adhesion of the 16" all-season tires, it tightens up nicely and gives reasonably good feedback. Someone who was more inclined to explore the sporting side of the Jetta might want to replace the rubber with something more aggressive, which would likely give even better feedback.

Under all normal driving conditions the stock tires are quiet and only start to exhibit some noise as the limit is approached. Controlling the Jetta is easy for the driver, thanks to seat that keeps the operator planted directly in front of the thick rimmed steering wheel.

Fuel economy is highly dependant on driving style and the Jetta is no exception. Renowned "fuel stretchers" John and Helen Taylor are currently in the midst of an 8,000 mile drive through all 48 contiguous states in a Jetta identical to the one we drove. After 5,000 miles the pair were averaging 58.2 mpg and had topped 66 mpg on one stretch through Nevada and California. During our driving day, the top driver pairing achieved an average over the 125 mile route of over 44 mpg.

My co-driver and I decided to see what could be achieved while still exploring the fun to drive capabilities of the Jetta. Without making any attempt to conserve fuel we achieved an extremely average of 30.7 mpg.  

While cars like the Toyota Prius and Honda Civic hybrid offer exceptional fuel economy, the combination of small low rolling resistance tires means they are not particularly engaging to drive. For many, if not most drivers, who see getting behind the wheel as a necessary chore that is nothing more than a bridge between other activities, that's a perfectly adequate solution.

For those who prefer a less linear path from point A to B, Volkswagen offers a very balanced alternative in the Jetta TDI. By virturally matching the mileage of its hybrid competitors and meeting the toughest emissions standards in the world the Jetta still offers plenty of Fahrvergnügen. At a starting price of $21,990 for the sedan and $23,590 for the even more versatile SportWagen, the "Drivers Wanted" sign is now proudly hanging.