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didn't see this posted, some interesting facts about adblue, the urea for some next gen diesels

NIAGARA-ON-THE-LAKE, Canada — Audi released details of the long-awaited release of its TDI clean diesel engines in the U.S. and Canada. Next winter, in January 2009, 50-state compliant versions of the 3.0-liter TDI V6 engine will make the first stateside appearance in the successful Audi Q7 crossover SUV.

Audi could have released TDI engines in the U.S. sooner, but opted to wait until the new ultralow-emissions system (ULES) was ready to meet the more stringent California Air Resources Board (CARB) requirements so it could sell diesel power in all 50 states and Canada.

Currently, a handful of Western and Northeast states adhere to CARB requirements. By model-year 2009, the number of CARB states jumps to 11. Included among them are several states where Audi sales are significant.

Technological improvements employed by Audi to meet CARB's low-emissions-vehicle (LEV) tailpipe standards — equivalent to federal tier 2, bin 5 — include cylinder pressure sensors, NOx sensors, revisions to the variable-geometry turbocharger and exhaust gas recirculation (EGR) system, a urea injection system called AdBlue and a second exhaust catalyst.

The AdBlue system sprays small amounts of a urea solution just upstream of the new DeNOx catalyst, where it reacts in the heated environment to reduce NOx emissions. AdBlue is stored in a 6.2-gallon tank — enough to last to the next scheduled oil change.

Test-driving a Q7 equipped with the 3.0-liter V6 TDI engine provided at the event revealed that common U.S. perceptions about diesels are, in fact, outdated misconceptions. This Q7 is quiet, starts quickly, idles smoothly and accelerates smartly. There is no soot or smell. About the only way to tell is to look at the tach; it redlines at just 4,600 rpm.

But that's merely a reflection of a diesel engine's strength: lots of torque at low engine rpm. The U.S.-spec 2009 Audi Q7 3.0 TDI is expected to be rated at 221 horsepower, but a generous 406 pound-feet of torque is available at just 1,750 rpm. These specs are nearly the same as the standard 3.0-liter TDI now sold in Europe.

Final certification of the U.S.-spec TDI is not complete, so EPA fuel economy figures were not available. But Audi TDI Development Manager Gunter Schiele said that extensive U.S. road tests are ongoing and fuel economy has so far averaged "about 25 mpg." With a 26-gallon tank, expect the TDI Q7 to cover 600 miles on one tank.

For comparison, 2008 Audi Q7s with the gasoline 3.6-liter V6 are rated at 14/20/16 mpg (city/highway/combined); the 4.2-liter V8 gasoline engine is good for 12/17/14 mpg. Both require premium unleaded fuel.

Audi has confirmed the "what?" and "when?" aspects of the return of diesel-powered Audis in North America. What we didn't learn is the "how much?" Pricing and final specs will not be released for some months. Stay tuned here for further updates.
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