[whthorse86]

I just installed a boost/vac gauge, the needle stayed in vacuum if I rev in neutral, only reved it to 4000. Is this normal? When I took it for a ride the boost came on at 3000 and developed 10 PSI @6000. While driving if I get the boost up, then come off the throttle and throttle up to 4000 and keep it there, the boost goes away. Should the boost be constant @ a certain RPM, say 2 PSI at 3300 and 5 PSI at 4000 and so on? Is this belt slippage or bypass issue or normal? any help is appreciated. Thanks!

[BlueStreak03]

Boost is more loading dependent than engine speed dependent. Also it depends a great deal on throttle blade position. If your blower is spinning it's heart out and you're only at 1/4 throttle, then the throttle blade is only going to pass as relatively small amount of air into the intake manifold where boost is measured ( I assume this is where your boost gage is located. If you were to put the same boost sensor into the discharge pipe of the blower then you would 'see' more boost. Manifold pressure is what counts though, not discharge pipe pressure.

[whthorse86]

Thanks BlueStreak03, this makes it clear to me. It seems that that the car is working as it should. Now I must focus on the tune...