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Posted by Desoto61 [138.162.0.46] on Monday, July 19, 2010 at 13:18:08 :
In Reply to: Re: engine brake posted by clueless [201.202.25.26] on Monday, July 19, 2010 at 12:34:52 :
There's two methods to do this on a diesel. The original "Jake Brake" is a mechanism built into the motor that allows the exhaust valve to open during the compression stroke, before fuel is injected. This way the engine has to work to compress the intake air, but it's released before fuel is added and power is made. They can dial in how early the exhaust valve opens to control how much engine brakeing they get.
The smaller diesels, like in some 3/4 and 1 ton domestic models, have a valve in the exhaust piping that restricts flow and makes the piston work against the back pressure during the exhaust stroke. Ideally it would also de-fuel the engine while engaged.
Gas engines are not designed as robustly as a diesel engine and the high back pressure of an exhaust brake could damage them.