Fuel pressure up after Walbro install
01-08-2003, 12:21 PM
#1
Fuel pressure up after Walbro install
I got one of the Walbro fuel pumps through the recent group deal. After installing it last weekend I noticed that the fuel pressure at idle is at 38-39 psi, up from 34 psi. Pressure at WOT appears to be unchanged at 43 psi, or at most it hits 44 psi.
Anybody else notice this behavior?
My EGT readings appear to be unchanged, about 800F at idle, 1100F cruising at 65 mph, so I guess the ECM is compensating for the additional fuel pressure by shortening the injector pulses. Haven't checked EGT at WOT, but since the pressure is the same as before at WOT, the EGT is certainly the same.
EDIT - I took a closer look at my fuel pressure gauge during a WOT run last night, and it appears I was wrong about the FP being unchanged at WOT - the WOT fuel pressure is at about 50 psi. I didn't run long enough to get a good EGT reading.
Anybody else notice this behavior?
My EGT readings appear to be unchanged, about 800F at idle, 1100F cruising at 65 mph, so I guess the ECM is compensating for the additional fuel pressure by shortening the injector pulses. Haven't checked EGT at WOT, but since the pressure is the same as before at WOT, the EGT is certainly the same.
EDIT - I took a closer look at my fuel pressure gauge during a WOT run last night, and it appears I was wrong about the FP being unchanged at WOT - the WOT fuel pressure is at about 50 psi. I didn't run long enough to get a good EGT reading.
01-08-2003, 12:30 PM
#3
Originally posted by SprintMax
if its the 255 lph.. it goes up.. you gotta use an Aftermark FPR to bring it back down
if its the 255 lph.. it goes up.. you gotta use an Aftermark FPR to bring it back down
01-08-2003, 01:02 PM
#5
Re: Fuel pressure up after Walbro install
Originally posted by Stephen Max
I got one of the Walbro fuel pumps through the recent group deal. After installing it last weekend I noticed that the fuel pressure at idle is at 38-39 psi, up from 34 psi. Pressure at WOT appears to be unchanged at 43 psi, or at most it hits 44 psi.
Anybody else notice this behavior?
My EGT readings appear to be unchanged, about 800F at idle, 1100F cruising at 65 mph, so I guess the ECM is compensating for the additional fuel pressure by shortening the injector pulses. Haven't checked EGT at WOT, but since the pressure is the same as before at WOT, the EGT is certainly the same.
I got one of the Walbro fuel pumps through the recent group deal. After installing it last weekend I noticed that the fuel pressure at idle is at 38-39 psi, up from 34 psi. Pressure at WOT appears to be unchanged at 43 psi, or at most it hits 44 psi.
Anybody else notice this behavior?
My EGT readings appear to be unchanged, about 800F at idle, 1100F cruising at 65 mph, so I guess the ECM is compensating for the additional fuel pressure by shortening the injector pulses. Haven't checked EGT at WOT, but since the pressure is the same as before at WOT, the EGT is certainly the same.
Why did you get the High Pressure pump are you installing nitrous?
Like Sprint said, thats normal for the HP pump and only way to get it down is with aftermarked FPR.
01-08-2003, 01:35 PM
#8
Originally posted by SprintMax
he has a Supercharger.. i think he might be going smaller pulley and not using the aux pump
he has a Supercharger.. i think he might be going smaller pulley and not using the aux pump
01-08-2003, 01:36 PM
#9
Are there any fuel pressure regulators that can raise the fuel pressure when on boost. ie.. so I can avoid buying the SARD + Vortech disc type fmu. All in one thingie. I already have the Vortech w/ the 6:1 disc and the Walbro(both not installed though)
01-08-2003, 01:44 PM
#10
Re: Re: Fuel pressure up after Walbro install
Originally posted by Jime
Your ECM does not check fuel pressure it assumes it to be in the normal 34-43 range, so it will not compensate if its too high. You many notice some difference if fuel mileage with it up that high.
Your ECM does not check fuel pressure it assumes it to be in the normal 34-43 range, so it will not compensate if its too high. You many notice some difference if fuel mileage with it up that high.
This is true at WOT. However, at part throttle (in closed-loop operation) the ECU will compensate for more pressure by shortening the injector pulsewidth. While it does not read fuel pressure, it will be able to tell what's going on via the O2 sensors.
01-08-2003, 02:05 PM
#11
Re: Re: Re: Fuel pressure up after Walbro install
Originally posted by mzmtg
This is true at WOT. However, at part throttle (in closed-loop operation) the ECU will compensate for more pressure by shortening the injector pulsewidth. While it does not read fuel pressure, it will be able to tell what's going on via the O2 sensors.
This is true at WOT. However, at part throttle (in closed-loop operation) the ECU will compensate for more pressure by shortening the injector pulsewidth. While it does not read fuel pressure, it will be able to tell what's going on via the O2 sensors.
Actually that will help me with a couple of other things I am working out right now. Thanks.
01-08-2003, 02:23 PM
#12
Actually, that's not 100% accurate, but still true...
Originally posted by mzmtg
This is true at WOT. However, at part throttle (in closed-loop operation) the ECU will compensate for more pressure by shortening the injector pulsewidth. While it does not read fuel pressure, it will be able to tell what's going on via the O2 sensors.
This is true at WOT. However, at part throttle (in closed-loop operation) the ECU will compensate for more pressure by shortening the injector pulsewidth. While it does not read fuel pressure, it will be able to tell what's going on via the O2 sensors.
Minor fact I know, but had to throw that in there for know-it-all Ben, since he beat me to it.
01-08-2003, 02:25 PM
#13
Re: Actually, that's not 100% accurate, but still true...
Originally posted by IceY2K1
According to my OBD-II scans you can also go Open-loop without being at WOT. I believe it happens for a QUICK rate-of-change, ie heavy throttle. For example going from 25% to 75% TPS in a short period of time.
Minor fact I know, but had to throw that in there for know-it-all Ben, since he beat me to it.
According to my OBD-II scans you can also go Open-loop without being at WOT. I believe it happens for a QUICK rate-of-change, ie heavy throttle. For example going from 25% to 75% TPS in a short period of time.
Minor fact I know, but had to throw that in there for know-it-all Ben, since he beat me to it.
I knew that.
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