Fuel pressure questions

[foolproof]

Join Date: November 2009
Posts: 5

I appreciate the advice that was given..what I did was I took a stock 5.0 HO that i had tuned with vacuum leaks. I was under the impression that the jag off that dyno'd it just added more fuel to compensate for the vacuum leaks that i found during this process, so I pulled the chip. Replaced the intake with a GT40 top and bottom trickflow spacer, SVO heads with 1.6 roller rockers, F303 cam, 70mm throttle body, stock Mass Air Flow....wasnt aware I was supposed to change it to compensate for the Fuel and Air. I bought a MSD Ignition Box 6al will this help hyper-tech coil pack? (Box not installed yet.) So do i just change the Mass Air Flow for the size injectors that i have? And i'll check for the pinched fuel line.
By the way.. How much fuel pressure is too much. It feels like the car should be more responsive..runs good but i think it should be a little more punchy. It used to idle at 38 and now at 43lbs.
And should I go get a new tune for that chip? The dude wanted to charge me another 300 bucks to tune it again. Thanks alot.

 

[mikepotts]

you dont want to set the fuel pressure at idle, ive seen cars with perfect fuel pressure at idle and underload it went to zero, as for yours, the fuel pressure you listed should be close... if you still have the stock mass air i would replace it with a 75mm pro-m. and go from there...

 

[HISSIN50]

What PSI were you at when the tune was done? It should have been at stock settings and then had the Inj-PW modified. The EEC assumes ~42 PSI at WOT.

If you still run 19's, I'd recommend a 94-95 MAF over an aftermarket unit.

You should not be needing much in the way of a tune right now. If there are issues, post up to see if they can be figured out.

Tangent: Mike, if you had a car with no FP at WOT, that was not a tune issue but a component failure.

 

[mikepotts]

Tangent: Mike, if you had a car with no FP at WOT, that was not a tune issue but a component failure.

yeah, as it turned out the car had a faulty mallory adjustable reg., believe it or not, we fixed it by putting the stock reg back on?! and this was a 377 w/ TW heads and 30lb. injectors ect...

 

[liljoe07]

Posted via Mobile Device

I never use an adjustable fuel pressure gauge on a N/A setup. As long as the stock is doing fine, it works just as good. 40-42 psi covers a lot of ground with the proper injectors.

Some guys don't realize that making small fuel adjustments don't do anything. As soon as the 02s detect a different 02 level, it just correct whatever adjustment you just made with the injector pulsewidth. So basically you adjusted for nothing.

 

[foolproof]

It idled at 38lbs and now its at 42lbs. I got a 70mm throttle body and you suggest get the 75mm MAF? So my fuel pressure being at 42lbs im good right?
Just get the MAF. Thank You. I'll reply next week if this works.

 

[mikepotts]

It idled at 38lbs and now its at 42lbs. I got a 70mm throttle body and you suggest get the 75mm MAF? So my fuel pressure being at 42lbs im good right?
Just get the MAF. Thank You. I'll reply next week if this works.

yep. or a C&L 73... i cant remember the size of the stock meter, but i know its 60 something mm, and you always want it larger than the t-body. if you get a C&L make sure it has the proper sampling tube for the size injectors you have, the PRO-M will have to be calibrated to injector size.