Irishpilot03

I've heard that an adjustable fuel pressure regulator on a slightly modified LT1 can yield up to 10 hp, but I've also heard that turning up the pressure will wear out the stock injectors and possibly damage the engine. What is the verdict, a good mod or not?




[Modified by Irishpilot03, 1:49 AM 1/28/2003]

Glasman66

ttt, I'd like to know also.

93LT1

Wear on the injector's is a new one for me. The real objective is reach the proper A/F ratio. You also need to be aware of the computers behavior. (ECM/PCM)
Hank

spdrcrj

I have one and can tell you that it's a very worthwhile mod. Use a fuel pressure gauge and make an adjustment, run it, adjust it, run it....etc. I only bumped my pressure about 4 or 5 lbs and it gave me a seat of the pants improvement. If you set it too high, there goes any fuel economy.

Irishpilot03

Sweet. What are you getting for fuel economy compared to what you had without the upgrade. Also, where did your Mid America lowering kit help you the most for cornering? And last, is your carbon-fiber kit actually a full kit that replaces your dash, or is it the cosmetic kit you put over your existing dash?


[Modified by Irishpilot03, 2:50 PM 1/28/2003]

fullboogie

It seems to me that it would be a worthless mod unless you have an A/F ratio gauge to see the results of your tuning. Take it to the track and tune your regulator with the gauge, and you're set. Otherwise, how do you know what's going on?

silver & red CE

94 and up Vette PCMs will automatically compensate for any changes you make to the fuel pressure. If you want to tweak your 94-96 LT1/4's WOT A/F ratio you'll have to reprogram the PCM, an AFPR is not going to do a thing except lighten your wallet.

This is a good mod for 93 and earlier Vettes.

Eric

all4c4lt4

:iagree: What he said.

Zora

Can not think of any Cons... :D

Gonzo

Thanks just saved me alot of time and effort

Irishpilot03

Thanks for the info....I think I'll go after something else like a TB bypass until I have more $ saved to go after bigger mods.

95AquaC4

I believe this to be true in closed loop mode. The computer will trim the injectors, and change the pulse width. However, at WOT (open loop) I believe your actual fp setting will be used. :yesnod:

Zora

:iagree: :yesnod:

silver & red CE

On 94 and up, the PCM will trim out any WOT changes in A/F due to changes in FP by using the closed loop values gathered as you drive down the road at part throttle. If you don't believe me, hook up a scan tool and change the FP, then go for a ride.

Eric

Rich_01659

I have a 94 with an AFPR and i can tell you that it makes a big difference if your FP is too low you will KNOW/FEEL it. As for too high , can't say for sure. I used the track and the feel of the power. Lower was bad ,higher was good.

Irishpilot03

So if the car is only using part of the throttle then the AFPR won't be adding anything, but under full throttle position, the AFPR will add hp? Is this right, and if there is anyone with data or times to prove one way or another whether it helps or not would be great.

1SLO POK

I have an 85, so are you saying that any adjustment I do on the AFPR will not be over-run by the computer? Meaning any adjustment I do I should notice a difference and not worry about being re-adjusted by the ECM.

silver & red CE

No this isn't correct. On older Vettes, the PCM doesn't use part throttle setting to calculate the WOT pulse width. On earlier Vettes the WOT injector pulse width is constant from the PCM tuning, not the case on later Vettes. On 94 and up, the PCM uses the part throttle pulse width to calculate the injector pulse width at WOT. This enhancement was done to keep your Vette inside emisson limits even at WOT. Any tuning that relies on FP to be constant will be quickley compensated for (on 94 and up). You guys should use something more scientific that the old SOP dyno, the placebo effect is very strong, esp when $100 has been wasted. Sorry I don't have any dyno graphs, but there's been plenty of info on this subject posted here and on the f-body digest.

The good thing is that on a 94 and up Vette an AFPR won't hurt your car as long as you keep the FP between the factory limits.

Eric

jmrl98

Yes 1SLO POK, you are correct. On our cars (I have an '85 also) the computer will not change the FP at WOT. According to TPIS, the reason that the 87-91 factory set FP is higher than our factory set FP was because TPIS found HP gains by upping the pressure on the 85-86's. I don't know how true it is that GM took their advice, but it is true that the 87 and later L98s have higher stock FP than our 85s. :seeya :steering:

95AquaC4

Well, I thought I knew this one. :( This may be the most valuable info I have learned here. :yesnod: I will try to remember this so as to help someone else in the future. Thanks! :cheers: