No vacuum to FPR.. Side effects?
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Well, not a good idea. The fuel pressure is designed to fluctuate with the amount of air going into the engine (whole air to fuel ratio principle) and the vacuum is drawn via the intake opening the f.p.r. keeping the ratios at even levels through the rpm range. Disconnecting the vacuum will cause fuel richness and lean concerns. I'd find something better to do.
Thanks.
I wasnt planning on removing it, but was curious as to the side effects of having it vacuumless. My intake is on backwards, and thus sits over the FPR and its an extremely tight fit.. Theres some question as to whether or not its getting vacuum and I was curious what sort of side effects would be noticed assuming its not.
I wasnt planning on removing it, but was curious as to the side effects of having it vacuumless. My intake is on backwards, and thus sits over the FPR and its an extremely tight fit.. Theres some question as to whether or not its getting vacuum and I was curious what sort of side effects would be noticed assuming its not.
Michael Yount
Mustang Master
If you were to put a fuel pressure gauge on the system, you'd see that when you apply vacuum to the regulator, it reduces the fuel pressure proportionately with how much vacuum is applied. At idle on a stock engine, the pressure will drop from about 39--40 down to 32 or 33 psi when vacuum is applied. As the previous poster described, the whole idea is to reduce the system pressure during low load (high vacuum) conditions when the engine doesn't need as much fuel. Keep in mind that's only one way fuel delivery is impacted. Once in closed loop, the O2 sensors work with the ecu to control air/fuel ratio by altering cycle time or pulse width (how long the injector is held open).
So, if you removed the vacuum hose or if it's getting pinched - you'd be richer during cold start up (open loop and higher fuel pressure). Once the system went into closed loop, the ecu would begin adjusting pulse width to try and reduce the amount of excess fuel that was being injected. Basically over time the adaptive strategies of the ecu would compensate for the higher pressure.
At wide open throttle, there'd be no impact from removing the vacuum line. Removing the vacuum line emulates what happens when you floor it - there's no vacuum in the intake then.
So, if you removed the vacuum hose or if it's getting pinched - you'd be richer during cold start up (open loop and higher fuel pressure). Once the system went into closed loop, the ecu would begin adjusting pulse width to try and reduce the amount of excess fuel that was being injected. Basically over time the adaptive strategies of the ecu would compensate for the higher pressure.
At wide open throttle, there'd be no impact from removing the vacuum line. Removing the vacuum line emulates what happens when you floor it - there's no vacuum in the intake then.
Hm.. Thanks ALOT.
That may explain a problem Im having. My motor is running VERY rich at idle, but once the engine gets good and warmed up, it leans out and drives considerably better. I pulled the FPR's vac line off the intake and plugged the intake hole with my finger.. I didnt notice any different at all, which could perhaps mean it doesnt have any (or very very little) to begin with.
I may pull my upper intake (again..) and see if I can find some way to bend the bracket on the fuel rail to drop the FPR down a little. Im worried its being pinched or restricted when the intake is on.
That may explain a problem Im having. My motor is running VERY rich at idle, but once the engine gets good and warmed up, it leans out and drives considerably better. I pulled the FPR's vac line off the intake and plugged the intake hole with my finger.. I didnt notice any different at all, which could perhaps mean it doesnt have any (or very very little) to begin with.
I may pull my upper intake (again..) and see if I can find some way to bend the bracket on the fuel rail to drop the FPR down a little. Im worried its being pinched or restricted when the intake is on.
Michael Yount
Mustang Master
Take a look at some of the other vacuum line fittings on the car. The thermactor and egr switches (firewall) have some 90-degree elbow fittings. One of those might work a little better on the fpr with the manifold sitting right over top of it.
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