[Build Thread] -- Journey to 700+ WHP [Supercharger]

[soill370z]

yeah base pressure should be set around 52 with vac off no matter what, never lower, never higher.

[Senna-F1]

Originally Posted by soill370z

yeah base pressure should set around 52 with vac off no matter what, never lower, never higher.

Since my 41 psi was with vacuum line connected and engine running, would the gauge have registered more had I unplugged it? Wondering what effect it has with line connected vs not connected.


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[soill370z]

Originally Posted by Senna-F1

Since my 41 psi was with vacuum line connected and engine running, would the gauge have registered more had I unplugged it? Wondering what effect it has with line connected vs not connected.


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yeah it would have came up a few psi, once you have vacuum on it, it drops a tad. with mine set at 52 , once i connect vac it drops to around 48-50 ish.

[turtle64b]

Originally Posted by Senna-F1

Since my 41 psi was with vacuum line connected and engine running, would the gauge have registered more had I unplugged it? Wondering what effect it has with line connected vs not connected.


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Yes. Your engine operates at a vacuum normally.

There is a piece inside the fuel pressure regulator that moves with changes in intake manifold pressure.

When you set it initially, it has to be a atmospheric pressure to give a good baseline for fuel pressure.

When idling (engine operating at vacuum), the regulator will send less fuel (pressure) to the engine since it does not need as much fuel to idle as compared to driving.

When you really get on it, that piece moves to allow less flow back (more resistance to flow), increasing fuel pressure proportional to intake manifold pressure, ensuring that the engine is getting the correct amount of fuel as pressure increases.