I think I understand what you are asking? A throttle blade does create braking on a gas motor. If you had a gas motor with 18 to 1 compression and let your foot off of the gas it would throw you right through the windsheild. Just the same as when you close the exaust brake on a diesel. There are 2 benifits I can see from having it on the exaust side. First it is just easier to put it on the exaust do to mounting issues and second, buy leaving the intake side open you are still allowing air to enter the engine further enhancing the braking potential. On a gas motor you are actually using vacum to slow you down. ???Edited by: Bronco
Engine braking is illegal in some places, but exhaust braking is not. Engine braking cuts the fuel and opens the exhaust valve right before TDC on the compression stroke. It can make a bunch of noise, although some of the newer ones do seem quieter. With an exhaust brake, a flap closes in the exhaust pipe and all you hear is a hiss as exhaust bleeds through a sized hole in the flap. If pressure gets too high, flap opens slightly. If not, exhaust valves would be opened with the pressure.
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