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 (http://forum.efilive.com/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....:D

[joecar]

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

[johnv]

If your not useing the vac/boost reference on the external regulator (which you don't need unless a FI setup)
Just set the rail pressure to 58 psi and your good to go (no PCM changes)

You may find your VE table a little off at high load/rpm if your factory pump was struggling to keep up before.

[joecar]

In that case (no vac reference) then the IFR is sloped.

[minytrker]

Well I am still having some weird issues that I have never seen before. The two inner cylinders (3,5 & 4,6) are normal and the two outer cylinders (1,7 & 2,8)are pig rich.

I have the fuel lines connecting into the back of each fuel rail and the regulator mounted inbetween the front of the rails.

[joecar]

I see, your FPR has a reference port but it is open (at BARO), so it behaves just like a non-referenced FPR (sloped AFR).

I don't see the return line, does it go under the manifold...?

To answer your original question: if your injectors are unchanged then you don't need to edit the injector tables (which are set for 58 psi rail pressure).

You do need to set your FPR to 58 psi rail pressure (measure with a gauge).

[joecar]

What happens if you swap the injectors from the outer cylinders with the inner cylinders...?

Also, check that all injector signals (at the injector connectors) are all correct... (a lab scope would be handy for this... ;) ).

This will show if the problem is with the injectors or with the wire harness, or maybe with the manifold (with your manifold pooling/wallwetting is different among runners).

How are you determining that the outers are rich and the inners are lean (post some pics of your spark plugs if that's how you're doing it...? Do you shutoff immediately after a run...?)

[minytrker]

I havent swapped injectors yet, I just ran these injectors on my old motor with no problems. The return line goes under the intake, and the psi is 58. Im reading the plugs, there is no questions on which cylinders are rich. I also shot each header tube with a laser and the 4 rich cylinders are all cooler.
The car may have a wiring problem, I just really noticed my guage cluser isnt reading correctly, I have no tach, and my temp gauge isnt reading. I can read the tach and temp with efi with no problems. My brake lights are also on all the time. I have removed alot of items from the car and harness but I also ran and drove the car like this earlier this year with no problems. The only thing changed now is the motor and I removed the whole transmission plug from the harness.