FPR - Do I need one?

2FastLX · 04-28-2001, 11:32 AM

I am wondering if I need to get a fuel pressure regulator to lean out my fuel a little bit after reading a few posts on it. I have 24lb injectors with stock ported heads, F303, GT-40 intake, 65mm TB, etc.

Do I need one and which one should I get? Aeromotive?

Thanks

jimberg · 04-28-2001, 01:26 PM

You can only "lean out" your fuel on the top end. Your computer makes the judgement on how much fuel you use and the only way to change that is with a chip, a programmable computer, or something like the SVO Extender. By reducing fuel pressure you will only be denying the computer how much fuel it can deliver on the high end by reducing the capacity of your injectors.

Some people will claim that they changed pressure, put it on the dyno, and then there was a big difference. The claim is true, but the problem is that the computer hasn't adapted yet. Drive a couple hundred miles, put it back on the dyno, and those number will be gone. At this point, the computer has stored new parameters to adapt to the new fuel pressure. Those dyno numbers will probably never be back, either, since the parameters it was using at the time were based on old samples.

If you, or anyone else, wants to be able to duplicate results received during the dyno, you would have to reset your computer just before doing the run. Find the best pressure for performance and then leave it there. Your computer will adapt, but the next time you race, you can reset your computer and the parameters will be back to what they were when you did your best run. This should last for a few races before it starts to adapt again.

A lot of people tend to think that these computer-controlled EFI cars can be tweaked like they are non-computer-controlled carbureted cars. We have MAF, ACT, ECT, O2, etc. sensors for the specific purpose of determining how much fuel should be metered out by the computer at different RPMs. People are nuts to think that they can tune their carburetor any better than the computer. It's like saying that you can pump your brakes better than anti-lock brakes can.

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351W 89 Mustang GT Convertible

2FastLX · 04-28-2001, 03:19 PM

So are you saying I don't need a fuel regulator until I get a chip?

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Too much to list. Best ET on the car so far with stock 2.73 gears - 13.73@102mph

Indiana Stangers Association
Buy your parts here
ICQ# 42269241

Mach 1 · 04-29-2001, 05:43 PM

No, you can get one without a chip and use it.
Most combos run better a little leaner. It may only lean it out on the top end (wide open throttle..see above) because you are in open loop (not using feedback info from the sensors to adjust fuel pressure...again, see above explanation) but that is still beneficial to you and can make your car perform better. Try 39 psi, then 37 psi, down to 35 for the best results, but dont go any lower than that.

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1993 GT/AOD
'93 Mustang GT

04-28-2001, 11:32 AM	#1
2FastLX The Photoshop Guru Join Date: Feb 2001 Location: Mecca, Indiana Posts: 1,419	FPR - Do I need one? I am wondering if I need to get a fuel pressure regulator to lean out my fuel a little bit after reading a few posts on it. I have 24lb injectors with stock ported heads, F303, GT-40 intake, 65mm TB, etc. Do I need one and which one should I get? Aeromotive? Thanks

04-28-2001, 01:26 PM	#2
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	You can only "lean out" your fuel on the top end. Your computer makes the judgement on how much fuel you use and the only way to change that is with a chip, a programmable computer, or something like the SVO Extender. By reducing fuel pressure you will only be denying the computer how much fuel it can deliver on the high end by reducing the capacity of your injectors. Some people will claim that they changed pressure, put it on the dyno, and then there was a big difference. The claim is true, but the problem is that the computer hasn't adapted yet. Drive a couple hundred miles, put it back on the dyno, and those number will be gone. At this point, the computer has stored new parameters to adapt to the new fuel pressure. Those dyno numbers will probably never be back, either, since the parameters it was using at the time were based on old samples. If you, or anyone else, wants to be able to duplicate results received during the dyno, you would have to reset your computer just before doing the run. Find the best pressure for performance and then leave it there. Your computer will adapt, but the next time you race, you can reset your computer and the parameters will be back to what they were when you did your best run. This should last for a few races before it starts to adapt again. A lot of people tend to think that these computer-controlled EFI cars can be tweaked like they are non-computer-controlled carbureted cars. We have MAF, ACT, ECT, O2, etc. sensors for the specific purpose of determining how much fuel should be metered out by the computer at different RPMs. People are nuts to think that they can tune their carburetor any better than the computer. It's like saying that you can pump your brakes better than anti-lock brakes can. ------------------ 351W 89 Mustang GT Convertible

04-28-2001, 03:19 PM	#3
2FastLX The Photoshop Guru Join Date: Feb 2001 Location: Mecca, Indiana Posts: 1,419	So are you saying I don't need a fuel regulator until I get a chip? ------------------ Too much to list. Best ET on the car so far with stock 2.73 gears - 13.73@102mph Indiana Stangers Association Buy your parts here ICQ# 42269241

04-29-2001, 05:43 PM	#4
Mach 1 Registered Member Join Date: May 1999 Location: Georgia Posts: 3,866	No, you can get one without a chip and use it. Most combos run better a little leaner. It may only lean it out on the top end (wide open throttle..see above) because you are in open loop (not using feedback info from the sensors to adjust fuel pressure...again, see above explanation) but that is still beneficial to you and can make your car perform better. Try 39 psi, then 37 psi, down to 35 for the best results, but dont go any lower than that. ------------------ 1993 GT/AOD '93 Mustang GT