Related: Automotive Powertrain
Frugality was hardly in style when Volkswagen Touareg TDI joined the fraternity of V10 trucks stomping around America in 2006. The 310-hp twin-turbo 5.0-liter diesel, which produces a massive 553 lb-ft of torque @ 2,000 rpm, could move the Touareg’s substantial girth of 5,825 lb from 0 to 60 mph in 7.5 seconds, tow 7,716 lb, and delivered 17 mpg city/22 mpg highway. (There was a 2.5 liter TDI Touareg, but that version stayed home in Europe).
Since then, VW has been embracing engine downsizing in a major way, such as developing a 3.0-liter V6 diesel that’s now available in the Touareg. It produces 225 hp and 407 lb-ft of torque, so it is still capable of towing 7,716 lb as the V10. While it is a bit slower (0 to 60 mph in 8.7 seconds rather than 7.7 seconds—although who is drag racing substantial SUVs?), it turns in better highway fuel efficiency—17 mpg city/25 mpg highway—and is 520 lb. lighter at the curb than its predecessor.
The V6 TDI is the first diesel in a new generation of V-engines from VW with a 90° bank angle. There is a 90-mm distance between the cylinders. The cylinder housing is vermicular graphite cast iron, which VW notes is 15% lighter than conventional cast iron. Along with its chain drive, the design principle makes for a very compact 17.3-in. long engine. A Honeywell/Garrett turbocharger provides boost.
The V10 may have been the first off-road, turbo-diesel, light-duty vehicle in the U.S. market with a particulate filter, but it still left its CO2 mark with 469 grams/mile; while the V6, coupled with an AdBlue (urea) after treatment system, puts out 420 grams/mile in combined city and highway driving.