What is the difference between an exhaust brake and a engine brake? - Diesel Forum

olddieseldude · 11-26-2006, 09:55 AM

Engine/Compression Brake...

Exhaust Brake...

Birken Vogt · 11-26-2006, 10:22 AM

An exhaust brake is a simple butterfly in the exhaust pipe that restricts exhaust flow to cause braking.

An engine brake (Jake brake) changes exhaust valve timing to match that of the injectors so that when the piston is at the top of the compression stroke, the exhaust valve(s) open and blow down the pressure that would have otherwise sprung the piston back down on the return stroke.

There are some new engine brakes by Mercedes and International that hold a valve open through the entire cycle of the engine and make less noise but supposably the same retarding force as a Jake style brake.

Anyway the engine brake (Jake style) works much better than the exhaust brake.

However it cannot be used for engines like ours because the brake taking the load off the exhaust side lifters when it lifts the exhaust valves out of time with the camshaft will cause the lifters to pump up and possibly the pistons to hit the valves.

Birken