Anyone happen to watch the Twelve Hours of Sebring road race a while back, in which Audi's new R10 *DIESEL RACE CARS* basically walked away from the field? What I found most amazing and amusing was that the car's diesel engine was so quiet that, in the upper gears, the wind noise was drowning out the engine note, so that the drivers HAD to rely on their shift lights to tell them when to shift gears. Imagine that - a diesel that's QUIETER than the normal gasoline engines they used to run...
A couple other items of interest on that car:
The gearbox was changed from a 6-speed to a 5-speed, with much wider gear ratios. Why? Two reasons. (1) The diesel makes so much torque that almost any gear is the "right" gear for that part of the course, and (2) the torque is so plentiful that the transmission required thicker gears, just to keep the engine from stripping the teeth off them! Cramming 5 thick-cut gears into the gearbox didn't leave room for a sixth gear.
The entire exercise was meant primarily to show U.S. consumers that diesels aren't necessarily slow, loud, or dirty. If I remember right, that Audi used a couple of particulate traps, but no mufflers of any kind. The figured the turbos would dampen the exhaust racket, and apparently, they were right. And the numbers I remember were something like 515hp/585tq, or thereabouts.
All of which is my long-winded way of saying that "diesel" isn't necessarily a dirty word anymore...
Mike