Has anyone every played with the idea of using only either the short or long intake runner on a VG30? I just read an article HCI where they put a new intake manifold on with only short intake runners and they noticed some power gains. I think it is vacuum controlled so it should be as easy as disconecting a hose.

 

I played around with that on my VE when I was on the dyno. by turning it on/off at different times, or leaving it on/off, I lost power every time. anywhere from 10 to 30hp...

we plugged it back in and let the car do it's own thing and had the best results in 6 dyno runs.

so my suggestion is simply to leave it alone.

 

the vg doesn't have dual length intake runners. that vacuum activated thing is a power valve. It's two butterfly valves that seperate the two chambers of the plenum, so of those two intake "runners" one feeds the front bank of cylinders and one feeds the back bank of cylinders. As to what the theory behind this valve is, I don't have a clue.

 

Actually, I think that is what's called a "dual-length manifold", since when the power valve opens it opens a hole between the runners and shortens the effective runner length down to where ever the valve sits. Close the valve and the runners work separately all the way to the butterflies.