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Old 07-28-2004, 11:22 AM   #1
scoobyimprza
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Default Normal range for fuel pressure

I'm gonna be getting a fuel pressure gauge to get some quirks in the car worked out and I'm wondering what range would be best. Thanks.

Brent
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Old 07-28-2004, 02:15 PM   #2
Hitokiri
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I don;t think my Fuel Pressure is normal....

but for the sake of more info its like this:

about 37ish idle spikes quikly up to 43-5 ish under light throttle, but hits low 50's under WOT,

I have a WRX pump on RS regulator and WRX inj.

Todd
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Old 07-28-2004, 03:03 PM   #3
HndaTch627
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43.5 psi @ idle with no vacuum applied to the fuel pressure regulator, after that the pressure will climb 1 psi for each pound of boost you apply

Hitokiri---any problems running the WRX pump without the fuel pump controller?? I was going to install one in my car for the nitrous kit and have since decided not to because i was afraid it would only over-fuel even more.

Jeremy
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Old 07-28-2004, 03:19 PM   #4
Wedge
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Supra Fuel Pump with SVX FPR.
Idle = 30psi
Full boost = 57psi
(18lbs boost)
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Old 07-29-2004, 12:03 AM   #5
scoobyimprza
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So do you think a 0-60 psi gauge would be good enough or should I go for 0-100?

Brent
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Old 07-29-2004, 08:02 AM   #6
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Go for the 100. Better safe than sorry. I bought the greddy. It's real nice. It reads in bar though.

Jason
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Old 07-29-2004, 10:43 AM   #7
maxiav
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53 psi easily @ idle on a walbro fuel pump.
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Old 07-29-2004, 01:03 PM   #8
Hitokiri
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HndaTch627: no problems. I am running WRX injectors as well and still no problems. I am not sure what you mean by the "fuel pump controler." It seems like it runs a little higher than the RS pump Fuel pressure wise, but I installed the gauge when I did the pump so I guess I don't know first hand.

I'll try taking off the vac line at idle and tell you what I read for base pressure. I'll get to it tonight.

Todd
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Old 07-29-2004, 03:51 PM   #9
HndaTch627
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Quote:
Originally Posted by Hitokiri
HndaTch627: no problems. I am running WRX injectors as well and still no problems. I am not sure what you mean by the "fuel pump controler." It seems like it runs a little higher than the RS pump Fuel pressure wise, but I installed the gauge when I did the pump so I guess I don't know first hand.

I'll try taking off the vac line at idle and tell you what I read for base pressure. I'll get to it tonight.

Todd
the WRX fuel pump doesn't always run at full output, there is a controller module for the fuel pump near the fuel tank on the WRX. If the fuel pressure isn't too much higher i may go ahead and throw it in, but when you are running a direct port nitrous kit 3psi in fuel difference is a HUGE difference in the power you make. I just would hate to have to buy another set of stainless jets since i just got the car jetted for what i think is perfect
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Old 07-30-2004, 12:03 PM   #10
IowaRS
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"NORMAL" naturally aspirated fuel pressure range from 28 at idle up to 40 psi or so at atmospheric pressure.
Anything out of this range and it's abnormal.

After that, for boost, it depends on the injectors that your are running and whether you are running a fuel computer or something similar.

Personally I have a Cartech Fuel Management Unit (mechanical, not electrical).
It's basically a rising rate fuel pressure regulator, but has the ability to start rising the fuel pressure while the intake is still in vacuum.

My setup:
Walbro 255lph
1.8L stock fuel pressure regulator
Cartech FMU
Stock Injectors

I idle at 30psi, by 0psi of boost I'm running 45psi of fuel pressure.
At 4.5psi of boost I'm at 74psi of fuel pressure.

The 45psi and 74psi are easily adjusted with the Cartech FMU.

Beware that the newer RS regulators can't handle the flow of a different fuel pump and will often give idle pressures above 40psi.

maxiav appears to have this exact problem.
53psi at idle is far too high unless you are using an electronic fuel controller to trim the injector cycle down. The problem with the 53psi is that as you give it more throttle and the rpms go up you actually lose fuel pressure, instead of gaining it.

One solution is to get an older pre-1998 regulator, many people have used the SVX regulators, but I think it's more of a year released issue. Obviously the 1.8 I'm using works perfectly.

Another solution is to go to dual RS regulators, one for each side of the injector rails.
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Old 08-02-2004, 01:23 PM   #11
scoobyimprza
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I put my fuel pressure gauge in before the fuel filter and I'm getting 28psi at idle. Here's my fuel mods:

WRX fuel pump
280cc Red top RS injectors
Apexi SAFC

Try different locations? Help me out. I have 370cc injectors I could put back in but I hate doing injectors.

Brent
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Old 08-02-2004, 02:38 PM   #12
IowaRS
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What kinds of issues are you seeing? What are you chasing?
What's the rest of your Turbo setup?
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Old 08-02-2004, 02:41 PM   #13
scoobyimprza
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The car is very very very lean. It's an EJ18 with a TD04 at 7psi.
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Old 08-03-2004, 12:15 AM   #14
scoobyimprza
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I'm looking at 44psi when I go into boost. I'm gonna put in a Walbro 255 and see what happens. We'll go from there....

Brent
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Old 08-03-2004, 07:21 AM   #15
Hitokiri
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i ripped of a vac line and hit almost 47psi! with a WRX pump and RS FPR. I idle at 38ish
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