Supercharged Cam Selection

[dirigo]

Does cam make a big impact when the motor is supercharged?

 

[mustube]

Yes, the valve overlap will make a big difference. The more overlap you have, the less charge will be held in the cylinder. So less overlap means that your engine will be compressing more air in the cylinder.

 

[350kmileford]

Doesn't overlap help some at higher rpm's though?

 

[mustube]

Doesn't overlap help some at higher rpm's though?

Yes, you do want some overlap. But too much is detrimental to your superchargers efficiency. I am by no means an expert on this subjuect, just trying to help out a little.

 

[Bort62]

I am not sure how familiar with fluid flow you are, but think about it this way...

Your engine is a restriction in a fluid system. The more air you flow through it, the more power you make.

There are generally two ways to flow more fluid through a restriction. One is to increase the pressure drop (raise the upstream pressure).

Turbo, Supercharger, and to some extent nitrous all do this.

The other is to raise the CV of the restriction, IE _ make it less restrictive.

Porting, cam, exhaust, bigger carb, etc (all your traditional modifications) all do this.

So increasing the pressure drop will increase power (supercharger) but also decreasing the restriction will increase it even more. You may be seeing less boost, but you will be making more power.

Make sense?

 

[rbohm]

8) when building an engine with a forced induction system, you usually have to lower compression ratios to prevent detonation at low rpm. when you do that you lose power, even with a supercharger. to minimize the power loss, you use a cam with less valve overlap to trick the engine into thinking it has a higher compression ratio than it really does. this also prevent you from blowing fresh air and fuel out the tailpipe rather than using it. at higher rpms you let the blower forced the air into the cylinder to maintain the higher rpm power.