Originally Posted by popatim
Come to think of it, I've never heard of any diesel being supercharged, only turbo'd.
It'* unusual, but they are out there. They aren't used in anything that would be driven on the road because supercharged diesels have a very small operating RPM range. They would mainly be used for things like pumps, generators, and industrial applications that require tons of torque at a constant operating RPM. Locomotives fall into tht category, because the diesel motor is only used to generate electricity, which powers electric motor that drive the wheels. They only have about a 500 RPM operating range.
A turbo varies boost by engine exhaust pressure. The more fuel/air used, the more boost there is. This means you can basically run a turbo diesel to any reasonable RPM and it will make the perfect boost for that RPM range and fuel/air mix.
An */C, however, varies boost by engine speed,so it will only make the exact right boost at a certain RPM and fall off sharply either side of the power peak. So basically, you design a */Ced diesel for a specific operating speed, and that'* all it does.