Direct Injection Gas Engines
With the trend to direct injection gas engines what happens going down a hill on compression. Diesel engines without intake butterflies have little hold back on compression, so I assume that gassers w...
Forum Discussion
BenK wrote:
Never looked closely into exhaust braking and admit to not really knowing how
they work.
From listening to them on the road, guessing that they block and release the
exhaust so that the pumping losses are increased. Therefore engine braking, but
that is just a guess till find time to read up on them (not motivated just yet
but if the direct injection systems do not have throttle's, then this might also
work on gasoline ICE's)
A exhaust brake is just a butterfly valve in the exhaust pipe. Or on the new light duty diesels with a VVT you close the turbo vanes. Either way you close the exhaust to increase backpressure, and pumping losses. The large diesels use a timed compression release. The exhaust valve is opened at TDC on the compression stroke, dumping the compressed air into the exhaust and not pushing the piston back down. The air dumping into the exhaust is what makes the noise you hear
