"The other thing is noise - over most driving conditions, our vehicle is a lot quieter," he said.
The iron cylinder block of GM's diesel engine has been strengthened, and the pistons have been redesigned to handle a lower compression ratio.
The compression ratio is 16.8:1 for the 2006 model engine, compared with 17.5:1 in the previous diesel.
The lower ratio reduces the clattering sound at idle associated with diesel engines, Weisbeski said.
Several acoustical changes were made to diesel-equipped GM vans to reduce interior noise, said Brian Mahnken, senior project engineer.
"From the carpet up, in front of the dash, we increased our barrier density," said Mahnken. "We switched to high-performance foam."
GM increased the thickness of sound-deadening material attached to the engine cover and on the floor. It also added Thinsulate heat and sound insulation in the step wells.
GM's 6.6-liter diesel engine produces 250 hp at 3,200 rpm and 460 pounds-feet of torque at 1,600 rpm. A heavy-duty four-speed automatic transmission is standard.
The engine is produced at the DMAX Ltd. plant in Moraine, Ohio, a joint venture between GM Powertrain and Isuzu Motors Ltd.
You may e-mail Rick Kranz at