Can someone explain the issue of compression braking on a diesel vs a gas engine? I don't mean an engine brake or an exhaust brake I mean just a simple downshift compression. I am told that with my diesel I should have an exhaust brake so when towing my trailer down steep grades, I can keep the speed under control. On my old gassers, that just required a downshift and let the engine compression hold me back. Why won't that work on a diesel?

 

There is no engine braking a diesel with out an engine brake. With a gasser there is a butterfly for the throttle in the intake so you have vacuum braking , whereas a diesel has no butterfly anywhere, it is a free flowing engine. An exhaust brake is a butterfly in the exhaust system giving a compression brake effect.

 

Thanks for the explanation. That makes perfect sense.