Volkswagen of America unveiled its cleanest diesel yet for the US, the Jetta TDI, at the Washington, D.C. Auto Show. (Earlier post.) The new clean diesel, which meets the 50-state EPA Tier 2 Bin 5 / CA LEV II emissions standard, will be available to the US market in the spring of 2008.
The 2.0-liter diesel develops 103 kW (140 hp) of power. The Jetta TDI—one of VW’s first BLUETEC products—uses a lean NOx trap to reduce NOx emissions by up to 90% percent instead of using urea Selective Catalytic Reduction.
The engine management system in the Jetta changes operating modes periodically to treat the NOx that has been stored in the catalytic converter. A particulate filter in the exhaust system further reduces emissions.
The goal of the BLUETEC initiative of Audi, Mercedes-Benz, and Volkswagen is to establish the concept of BLUETEC as a uniform label for clean and highly fuel efficient diesel-powered cars and SUVs with 50-state compliant engines. Technologies individually developed by each manufacturer serve to reduce NOx in particular.
For car models of the Passat class and smaller, Volkswagen is proposing its new lean NOx trap catalytic converter. At λ of greater than 1, NOx is captured and stored; at λ less than 1, NOx is released and reduced. Ultra low-sulfur fuel is a necessity, and fuel consumption will increase as a result of catalytic converter regeneration.
Larger and heavier models feature urea Selective Catalytic Reduction (SCR) catalytic converter (continuous) with the use of an aqueous solution such as AdBlue, transported in an additional tank made from stainless steel or plastic.
Another VW BLUETEC clean diesel—the Tiguan compact SUV—will also be available in the US in 2008.