Thread: Exhaust valves
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Old 10-17-2015, 04:12 PM   #2 (permalink)
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exhaust valves

Originally Posted by GreenSquirrel View Post
There is some merit to this although it's effect on mileage has yet to be credibly tested but here it is; exhaust valves create backpressure at low RPM's (when the engine is cycling smaller volumes of exhaust per minute) but open to allow full use of the cavernous exhaust pipe, it allows the engine to get a small bump in hp lower in the rev range, my question is has anybody tried exhaust valves to nurse the engine during acceleration at lower speeds for the purposes of mileage/fuel-conservation? I intend to give this a go on my next vehicle but would like to know what others know/have experienced about this subject.
At least one production motorcycle incorporated a 'smart' muffler which had a computer-controlled butterfly valve inside.
The motorcycle engine underwent a full-spectrum dynamometer test to evaluate it's best performance at all rpm's as a function of exhaust back-pressure,then a look-up menu was burned into the ROM chip which allowed the computer to modulate a servo motor linked to the muffler's valve; enabling the engine to always remain in the sweet-spot.
If you've got a loose $100,000 you want to throw at a chassis dyno,you'd be able to do this to your car.
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