Quote:
Originally Posted by Tim Ayers
I wanted to ask Pete this same question. My thought is a ram effect, but I'm really curious on the intake was able to lower the RPM's. I'm not doubting, but really curious on this works. I find it fascinating.
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Intake and exhaust tuning is used to move the peak torque or horsepower to a certain rpm range depending on the use of the engine.
If you will notice closely sometime, race teams that use one car to compete on several types or lengths of tracks, will use different configurations of exhaust headers and intake manifolds.
An excellent explanation of this was published in a book called "The Sports Car"
by Colin Campbell in 1961.
The basic principle of this is that the movement of the intake charge and the exhaust gas as interrupted by the valves causes pressure waves in the tubing it is traveling in. These pressure waves travel along the inner surface of the tubes building positive pressure ahead of them and negative pressure behind. If the tubing is cut to certain length, at a certain rpm the negative portion of the wave will occur precisely at the end of the tube and will cause a reflection of the wave. This reverse wave will travel back along the inner surface of the tube till it gets to the valve seat when it will meet the new wave and be reflected and reinforced causing a slight vacuum. This vacuum is what gives the incoming charge or the outgoing exhaust a boost in speed and increases engine efficiency.
There are several other design parameters involved in using this system but this is the basic.