Injector Data for return style fuel system

[minytrker]

I just installed a fuel cell and new complete fuel system in my 99 Z28, nothing was reused. I now have a regulator mounted to the fuel rails and a return going back to the tank. Do I need to change anything with the injector tables for this? The pcm is still turning on the fuel pump but the ext reg is controlling pressure.

[5.7ute]

Unless you have changed from a manifold referenced system to a non referenced or vice versa you will not need to change anything as long as the working pressures are the same.

[joecar]

B4001 has to be flat (same value in all cells) now since the manifold-referenced regulator now keeps the pressure difference across an injector constant...

all cell values are equal to the value for MANVAC=0 in the spreadsheet.

[minytrker]

B4001 has to be flat (same value in all cells) now since the manifold-referenced regulator now keeps the pressure difference across an injector constant...

all cell values are equal to the value for MANVAC=0 in the spreadsheet.

When is that needed, only when the regulator is between the fuel rails? What about with a corvette regulator back by the tank? I have my reg between my fuel rails on my car.

[joecar]

The IFR table is flat when the FPR has an air hose connecting it to manifold pressure/vacuum (this is called "manifold referenced")...

A manifold referenced FPR is typically located on a rail, or between the rails, and has a return line going back to the tank.

The regulator located near/in fuel tank is not manifold referenced (and so has a sloped IFR table)...

1997 LS1 Y-body uses a manifold referenced FPR.
1998+ LS1 Y-body and 1998+ LS1 F-body use a non-referenced regulator.

More info (if you are math inclined): showthread.php?t=4821

[joecar]

If your FPR is between the rails, check that it has:
- an air hose going to the intake manifold,
- a return line back to the fuel tank.

It should have both.

This regulator keeps the pressure difference across any injector constant:

if FPR base absolute pressure is FP+BARO, then:
absolute pressure on top of injector = FP+BARO+MAP (since manifold referenced)
absolute pressure on bottom of injector = MAP
difference of absolute pressures = FP+BARO = constant (regardless of MAP) -> IFR table is same value all across ("flat").

IFR is proportional to squareroot of pressure difference.


(side note: absolute pressure = gauge pressure + BARO)

[minytrker]

If your FPR is between the rails, check that it has:
- an air hose going to the intake manifold,
- a return line back to the fuel tank.

It should have both.

This regulator keeps the pressure difference across any injector constant:

if FPR base absolute pressure is FP+BARO, then:
absolute pressure on top of injector = FP+BARO+MAP (since manifold referenced)
absolute pressure on bottom of injector = MAP
difference of absolute pressures = FP+BARO = constant (regardless of MAP) -> IFR table is same value all across ("flat").

IFR is proportional to squareroot of pressure difference.


(side note: absolute pressure = gauge pressure + BARO)

I dont have - an air hose going to the intake manifold

but do have a return going to the tank off the reg.

[joecar]

Can you post a picture of that...

[GAMEOVER]

Good info in here....

[joecar]

Does the FPR body have a port/nub that looks like a vac hose would fit...?