guver - A deisel enginre dervives torque from increased compression. A deisel engine the same size as a gas engine will produce far more torque at a far lower rpm.

Example:

VW Jetta 2.0L 4cyl 8valve gas engine - 115hp, 102lb/ft@4800rpm

VW Jetta 1.9L 4cyl turbo deisel engine - 91hp, 155lb/ft@1800rpm

as you can see the deisel far exceeds the gas engine in both the amount of torque and the rpm at which it maxes out. I have driven this car, and the engine has so much torque at such a low rpm, that you can put it into first - not give it any gas - and dump the clutch, it wont stall - it will actually begin accelerating on its own without applying the gas, just based on the amount of torque it has at idle rpm.