A while ago, I swapped my fuel system to a return setup using a contour fuel rail, an aeromotive 13102 FPR (http://aeromotiveinc.com/products-pa...unt-regulator/), and a walbro 255. I wired it up using the guide from this forum. It uses the FPDM to trigger a relay to run the pump with a constant battery voltage. The car ran great, but threw two codes. One for the FPDM being unhooked and the other for the fuel rail pressure sensor being disconnected.
P1238 Fuel Pump Secondary Circuit Malfunction
P0193 Fuel Rail Pressure Sensor Circuit High Input
I've been learning about how to tune the ECU with the SCT PRP but I'm still confused on how to tune for the return setup.
I've learned that while the FRPS is not actually NEEDED, it seems alot of mustang guys are going to a return setup and keeping the FRPS to datalog and retain the injector pw compensation for varying fuel pressure.
This is what I'm trying to achieve.
I've found an aeromotive adapter for the FRPS
I believe that I can run a line from the 1/8npt port on the FPR to the adapter plate and it should give me an accurate reading of the regulated fuel pressure. This would allow me to retain the FRPS with the return setup. I'm also pretty sure I can retain the stock fuel pump / fpdm wiring though it might be a good idea to upgrade the power wire to the pump since it's going to be running a constant ~12v.
From my understanding (please correct me if I'm wrong), the pressure sensor is used for two things:
1. to tell the PCM how much voltage the pump needs to achieve the desired pressure drop
2. to adjust injector PW to compensate for changes in fuel pressure
If my understanding is correct, then I believe I have to command 15v in the fuel pump voltage table to get the pump to run 100%. I've also read that I need to set the PID gains to 0 so that no learning occurs. Is there anything else I need to change in the tune since I'm keeping the FRPS?
- I don't really understand what the fuel pump PID gains do and was hoping someone could explain in more detail.
- I know there's a variable to change the fuel system type from returnless to return style but what exactly does this do in terms of the ECU?
- I also noticed there's a variable "Injector Comp for Pressure". When set to 0, the PCM does not rely on the fuel pressure sensor to adjust injector PW. When I had the car running with no FRPS, I must have not been getting injector compesnation for fuel pressure and the engine ran pretty well. Would setting this to 0 have the same effect as running without the FRPS altogether?
- Under the Returnless Fuel Pump section, there's a Fuel Rail Pressure table. The description says this is only used on mechanical returnless setups without a FRPS.
- Under the Fuel Injector section, there's a Fuel Injector Pressure Drop table. The description says it's only used on a mechanical returnless system.
- I datalogged the pressure drop across injectors and "fuel_rail_pressure" with the FRPS unplugged. The pressure drop showed 39.69 (value for pressure drop across injectors). while "fuel_rail_pressure" showed 70 (the max value under the Pressure Sensor Transfer Function).
- When I unplug the FRPS, what table does the PCM use to assume it's fuel pressure reading from? I'm guessing it assumes the max reading from the sensor since the signal voltage is the same as the reference voltage (5v).
DJ / Producer at0m ActivE
I don't know exactly how you have the fuel rail plumbed, but you should be able to run the contour fuel rail and a focus (and possibly a contour) FRPS without needing the aeromotive adapter. I am using a contour rail and focus FRPS that could easily be converted to return-stylr as I have fuel lines running to each side of the rail. I just chose to keep the returnless operation for my setup. If the adapter is needed, just plumb the adapter between the rail and FPR.
Upgrading the wiring to the fuel pump is definitely a good idea. Keeping the stock wires while telling the ECU/FPDM to run the pump wide-open all the time could be asking for trouble.
The fuel pump PIDs are essentially variables in an equation(s) that the PCM uses to adjust fuel pump operation based on expected input/output and received input/output and transient operation (i.e. WOT to no throttle, shift, back to WOT)
The fuel system type variable tells the PCM to control the fuel pump/FPDM using variable duty cycle (returnless), constant duty cycle (return), or off/low speed/high speed operation.
With Injector Comp for Pressure set to 1, but the FRPS unplugged the PCM would be operating with a constant compensation factor based on the Fuel Injector Pressure Drop value as this would be the only value the PCM has defined with removal of variable PCM control of the fuel pump. With the value set to 0, there is no compensation factor. Either way there is no fine tuning for the fluctuations in fuel pressure due to timing/delay of electrical signals and/or mechanical operation of the FPR.
The Fuel Rail Pressure Table is probably left over coding from prior technology from earlier PCMs.
Fuel Injector Pressure Drop is where you define your "base" fuel pressure or the constant pressure differential that the FPR will maintain between the rail and intake manifold.
It seems you may have already found this based on the info provided, but this is what SCT as to say about settings that need to be changed:
Go into Returnless Fuel Pump > Fuel Pump Voltage Table > Set the entire table to 15’s.
Go into Returnless Fuel Pump > Desired Pressure Drop Across Injectors > Set the Right Column to ~10psi above the Regulator Pressure you are running.
Go into Returnless Fuel Pump > Scalar > Set Fuel Pump Gain Derivative Term to 0
Go into Returnless Fuel Pump > Scalar > Set Fuel Pump Gain Integral Term to 0 Go into Returnless Fuel Pump > Scalar > Set Fuel Pump Gain Proportional Term to 0
Returnless Fuel Pump > Scalar > Set Fuelpump Tst Pressure Below to Allow Test to ~20psi below the Regulator Pressure you are running
Go into System Switches > Scalar > Set Fuel Pump Type to 0
Go into System Switches > Scalar > Fuel Pump System Type to 0 (if present)
Last edited by straightupmad; 06-25-2012 at 08:15 PM.
Thank you so much man, I really appreciate your help.
The fpr that I'm using is a drop in replacement for the contor fuel rail.
Do you have a picture of the focus FRPS that you're using?
Your fuel rail configuration does not match the rail I am using. My rail is essentially a straight tube that you can see from one end to the other and the fittings/FRPS connect directly to the rail ends.
Here is a picture of the FRPS I am using.Attachment 21537
With this style, fuel flows straight through the FRPS.
With your case, I believe you are in fact going to need the previously discussed adapter.
Your link doesn't work. But I'm pretty sure you're using this fuel rail ?
Yes, that's the style I'm using.
What is the advantage of a Contour fuel rail over stock ZX2?
This is the only view you should see when on the road with my S/R!
I'd hit it really hard too!
There is no performance advantage in using another fuel rail. The different fuel rails discussed in this thread have been based on modifications (e.g. different intake manifold or fuel system layout) that make using a readily available fuel rail easier than modifying the stock rail.
I just noticed something in the PRP software. When you change the 'fuel pump type' to 0 (single speed pump), it gets rid of the 'returnless fuel pump' section in the category list. The 'returnless fuel pump' section is where the fuel pump voltage table, fuel pump gains, fuel pump error test, pressure drop across injectors, and a few others are defined.
So in switching 'fuel pump type' to 0, I'm assuming that the values defined for the voltage table, gains, etc, are not even being used...am I right? Do I still need to define these like you mentioned (voltage table to 15's, gains to 0, pressure drop across injectors, etc) ?
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