Quote:
Originally Posted by Full Throttle
This is correct
You dont, the moment positive manifold pressure is created the exhaust needs to be as least restrictive as possible. Especially with Roots blower that make their peak boost at very low RPMS
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The point of an exhaust to a car isn't just for reducing sound or piping the fumes away from the driver.
Exhaust and intake alike follow the laws of fluid dynamics. I'll explain it so someone like Full Throttle can understand...
Think of drinking a soda through a small straw. If you drink really fast and then remove your mouth, there were still be some soda that forces its way up and out through the straw. If you use a much bigger straw, you'd need a much larger force to have the same thing happen since there is much more volume of soda inside that straw.
The same thing happens in your exhaust at the exhaust valves. Exhaust trying to exist your pipes will create a low pressure area (think of a mini-vacuum) at the other end of your exhaust which is at the motor's exhaust valves. When those valves open up, the exhaust trying to escape your pipes will help 'pull' the spent exhaust exiting your cylinder while also helping in the 'fresh' air/fuel in (assuming there is some valve overlap which there probably is).
Full Throttle is correct that you want to maximize the amount of air pushing into your motor (high pressure at intake valves). For optimizing, you also want to utilize a properly tuned exhaust (low pressure at exhaust valves). Fluids/Air will flow fastest between higher differences of high/low pressure.
Our motors aren't pushing enough air that a full open exhaust would be warranted or desired.