Interesting fuel pressure
03-05-2008, 09:53 AM
#1
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Thread Starter
Interesting fuel pressure
Hey guys, just wanted to share some info and ask some opinions:
My car normally runs at 59 PSI fuel pressure (fuel pressure gauge indication) dyno of 202 whp
everything seems fine
yesterday ,while driving the car home, I noticed that under different loads in 4th gear (1/4 tank left) the fuel pressure seems to drop.
at small throttle, the pressure would still be 59
but if I go half throttle, it would be at about 58 ish
and at full throttle, it drops to 57 ish
fuel pump dying?
My car normally runs at 59 PSI fuel pressure (fuel pressure gauge indication) dyno of 202 whp
everything seems fine
yesterday ,while driving the car home, I noticed that under different loads in 4th gear (1/4 tank left) the fuel pressure seems to drop.
at small throttle, the pressure would still be 59
but if I go half throttle, it would be at about 58 ish
and at full throttle, it drops to 57 ish
fuel pump dying?
03-05-2008, 11:33 AM
#7
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iTrader: (7)
doesn't seem like much fluctuation; probably has to do with the level of fuel.
03-05-2008, 11:38 AM
#8
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Thread Starter
i have....10295 miles on my car, its never been replaced
the car still seems to run fine though, so I'm not worrying too much on it, just want to anticipate any problems since I'm getting all my stuff ready for the big mod-fest
the car still seems to run fine though, so I'm not worrying too much on it, just want to anticipate any problems since I'm getting all my stuff ready for the big mod-fest
03-05-2008, 11:43 AM
#9
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iTrader: (7)
details on 'mod-fest'? Inquiring minds want to know...
03-05-2008, 11:48 AM
#10
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Thread Starter
just all the stuff that has been sitting in my place for the past 3 months all together which never made it into the car, just need to put them all in sometime this month 
oh and a new paint job
oh and a new paint job
03-05-2008, 04:26 PM
#12
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Thread Starter
thanks guys, I was starting to think I have to shell out some mod-money to fix her 
btw, she's proved to be resilient and more enduring than I can ever imagined, what with all the nitrous and everything :D
btw, she's proved to be resilient and more enduring than I can ever imagined, what with all the nitrous and everything :D
03-05-2008, 09:43 PM
#14
we have a two speed pump that is switched by various commands. start up for instance is one. were you in a load situation with rpms over 5K and tps at more than 50%?
we are finding a 5-7% difference in readings over a fairly short period of time.
low fuel will not affect pressure until the pump can't pick any up and then the car will shut off/stumble.
I advise that no one ever let the tank go under 1/2 full.
It usually is not really a problem unless you go fi or you track your car.
we have a problematic fuel delivery system--still remains to be seen if it is filter, or the pump causing problems.
olddragger
we are finding a 5-7% difference in readings over a fairly short period of time.
low fuel will not affect pressure until the pump can't pick any up and then the car will shut off/stumble.
I advise that no one ever let the tank go under 1/2 full.
It usually is not really a problem unless you go fi or you track your car.
we have a problematic fuel delivery system--still remains to be seen if it is filter, or the pump causing problems.
olddragger
03-05-2008, 09:46 PM
#15
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Thread Starter
yes OD, its what you said, and the tps was over 50% as I stated before, it happens at any given rpm above 4k for me
it doesn't do anything to the power delivery
just a slight variation in fuel pressure
I plan to up to a 100 shot once i get the EMU to work properly and go from there, but i gotta buy some stuff of CRH first
it doesn't do anything to the power delivery
just a slight variation in fuel pressure
I plan to up to a 100 shot once i get the EMU to work properly and go from there, but i gotta buy some stuff of CRH first
03-06-2008, 01:11 AM
#18
The tank can be run nearly dry and the pump won't loose its scavenging.
I know there have been a couple of people with a pickup problem at low fuel levels, but that is an anomaly.
A properly installed, healthy pump doesn't care what the fuel level is as long as the pickup is submerged.
I suppose if you stayed at a continuous lateral load long enough to generate sufficient centrifugal force to move all the fuel to the right saddle tank, you could starve the pump, but that would mean nearly a full g in a left turn and less than a gallon in the tank. Even then it is unlikely.
A few PSI drop under load is normal - the pump works against a restriction - low injector duty cycle.
When you romp on it, the pressure drops because the restriction drops.
This is a returnless system, so the pressure regulation is built into the pump vane clearance.
I know there have been a couple of people with a pickup problem at low fuel levels, but that is an anomaly.
A properly installed, healthy pump doesn't care what the fuel level is as long as the pickup is submerged.
I suppose if you stayed at a continuous lateral load long enough to generate sufficient centrifugal force to move all the fuel to the right saddle tank, you could starve the pump, but that would mean nearly a full g in a left turn and less than a gallon in the tank. Even then it is unlikely.
A few PSI drop under load is normal - the pump works against a restriction - low injector duty cycle.
When you romp on it, the pressure drops because the restriction drops.
This is a returnless system, so the pressure regulation is built into the pump vane clearance.
03-08-2008, 05:21 AM
#20
is adjusting valve lash
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wtf? and i thought he was seeing something like 4-5 psi like its a carburetor car...
and with driveability issues... i thought this was gonna make me scratch my head.
and with driveability issues... i thought this was gonna make me scratch my head.
03-08-2008, 10:24 AM
#21
The tank can be run nearly dry and the pump won't loose its scavenging.
I know there have been a couple of people with a pickup problem at low fuel levels, but that is an anomaly.
A properly installed, healthy pump doesn't care what the fuel level is as long as the pickup is submerged.
I suppose if you stayed at a continuous lateral load long enough to generate sufficient centrifugal force to move all the fuel to the right saddle tank, you could starve the pump, but that would mean nearly a full g in a left turn and less than a gallon in the tank. Even then it is unlikely.
A few PSI drop under load is normal - the pump works against a restriction - low injector duty cycle.
When you romp on it, the pressure drops because the restriction drops.
This is a returnless system, so the pressure regulation is built into the pump vane clearance.
I know there have been a couple of people with a pickup problem at low fuel levels, but that is an anomaly.
A properly installed, healthy pump doesn't care what the fuel level is as long as the pickup is submerged.
I suppose if you stayed at a continuous lateral load long enough to generate sufficient centrifugal force to move all the fuel to the right saddle tank, you could starve the pump, but that would mean nearly a full g in a left turn and less than a gallon in the tank. Even then it is unlikely.
A few PSI drop under load is normal - the pump works against a restriction - low injector duty cycle.
When you romp on it, the pressure drops because the restriction drops.
This is a returnless system, so the pressure regulation is built into the pump vane clearance.
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