Fuel Pressure gauge/regulator placement/order......need a QUICK answer please

[jspaeth]

Getting ready to install my external Aeromotive FPR.

Stock setup goes like this (for me).........feed, fuel filter, through FP gauge, into fuel line, stock FPR is on the OUTLET side of the fuel rail, then to return.


Now, when I use an external FPR, does it also have to be positioned on the OUTLET side of the fuel rail, or can it go before?

I ask because currently, the car is tuned with the FP gauge BEFORE the fuel rail, so I want to keep it there for consistency sake.......however, the new FPR has a port on it for the gauge to screw directly into....

Thus, my question is as follows.......is it okay to position the FPR BEFORE the fuel rail rather than on the OUTLET side?


thanks all

[UNISA JECS]

All FPR's have to be placed on the outlet side or else it would never make any pressure. Think of the FPR regulator as the door stop. The fuel pump provides the volume (flow), the FPR turns this volume (flow) into pressure by regulating the rate of return.

[gippy87]

also if im not mistaking you may need some sort of adapter that deletes the stock fpr so you can hook up a hose from the rail to the new fpr then to the return line.

[UNISA JECS]

Yea deffinantly you cannot piggy back off the stock fuel pressure reg. unless your only need is to raise fuel pressure but even then I would not do it. If you dont have an adapter you can always drill a hole threw the stock fuel pressure regulator (the part the fuel goes threw).

[jspaeth]

All FPR's have to be placed on the outlet side or else it would never make any pressure. Think of the FPR regulator as the door stop. The fuel pump provides the volume (flow), the FPR turns this volume (flow) into pressure by regulating the rate of return.

This is what I figured, but I just wanted to make sure.....so, then when stock FP is measured, is it measured before or after the fuel rail?......because the FPR has a port on it for a FP gauge (which i already have inline BEFORE the fuel rail).

also if im not mistaking you may need some sort of adapter that deletes the stock fpr so you can hook up a hose from the rail to the new fpr then to the return line.

Thanks, already got that...

[ross.cottrill]

yep hes correct.you have to get an adapter for the end of the rail where the stock fpr goes.i got an hks one and i will get the part # for you if you want.(im using the same aeromotive fpr as you).

[jspaeth]

Okay just checked the FSM and the reference value for the fuel pressure (36 psi or whatever) is measured between the fuel filter and INLET to the fuel rail.......obviously, measuring on the outlet side will read a lower FP



Also, I already have the fuel rail adapter..........I am just trying to figure out where to put the gauge.......because ideally, I'd like to put the gauge right in the port on the FPR, but then the FP reading is AFTER the fuel rail, and I can no longer use the FSM values (as well as those that I used when being tuned) as reference values for my fuel pressure

[WoolyS14DET]

On the return line and def need an adaptor that are avail all over the place.
Dont foreget to set it correctly !!(43psi) Sounds like oyu got it all figured out !!

[UNISA JECS]

Okay just checked the FSM and the reference value for the fuel pressure (36 psi or whatever) is measured between the fuel filter and INLET to the fuel rail.......obviously, measuring on the outlet side will read a lower FP



Also, I already have the fuel rail adapter..........I am just trying to figure out where to put the gauge.......because ideally, I'd like to put the gauge right in the port on the FPR, but then the FP reading is AFTER the fuel rail, and I can no longer use the FSM values (as well as those that I used when being tuned) as reference values for my fuel pressure

Dont pay attention to the vacuum connected fuel psi (becasue this is variable engine to engine, elevation to elevation, one cam profile to teh next), instead just disable the source of vacuum to the FPR and set it at 43psi.

The resulting psi after connecting the vacuum source back to the FPR is directly related to how much inches or mecury (in/hg) your engine is able to pull.

Example:

If your engine pulls 20 in/hg, this is equivelant to 9.8psi........subtract 9.8psi from 43psi = 33.2psi, this is the pressure you should see if you had set your base fuel psi to 43psi when vacuum is attached you shoudl see 33.2psi.

[jspaeth]

I already understood this, but thank you anyway for the explanation.....

More particularly, I was referring to the fact that I am unsure of the pressure difference in the fuel between BEFORE and AFTER the fuel rail, so that 43 psi is meaninlgess if you are measuring the fp after the fuel rail.


Thanks all