3400 Impala Engine Mods

[WrathOfSocrus]

I will try it... i'll go from 19 to 21# and i think it'll be fine. thats pretty much going from my stock injectors to the 2000+ style injectors for my malibu.. I think my stft will always be in the negative as well as my ltft, but i cant see 2 lbs being outside what the pcm can compensate for.. by the way, i know what a tps and a maf and and map and 02 and bla bla bla... etc etc.. are.

It isn't a matter of what the computer can compensate for with the oxygen sensor. The oxygen sensor only comes into play when in closed loop. When you start your car you are in open loop mode and the engine runs off of predefined tables. Based off of those tables it sends a pulse to the injectors that tells it to open a certain amount for a given RPM, throttle position, and so on.

Changing the amount of fuel entering the engine per pulse by either increasing the fuel pressure or using a larger injector will result in more fuel being added than the computer expects. Small changes such as adding a few PSI to the fuel rail or installing a slightly larger injector might not drastically affect closed loop operation but will likely result in a rich condition in open loop. How rich would depend on the amount of extra fuel added and if the engine was already starved due to engine mods. It could be that the increase matches what the engine needs but the best way to know that would be through computer tuning.

Khipset - I'm not positive about all of the exact numbers but the method of figuring rate of fuel flow appears to be correct. There are also online calculators to help with the math if you are deciding between multiple injectors and need quick answers.

[Khipset]

Khipset - I'm not positive about all of the exact numbers but the method of figuring rate of fuel flow appears to be correct. There are also online calculators to help with the math if you are deciding between multiple injectors and need quick answers.

I have been using
http://www.rceng.com/technical.aspx

http://www.injector.com/injectorselection.php

and

http://www.csgnetwork.com/presskpapsicvt.html

For the math help. Thank God for Google. Just trying to make sure that when I do the change out and tune it that I have the correct info to input.

[SappySE107]

Did you test the fuel rail on a 4.2 or find the information somewhere? Google is giving me a bunch of stuff I don't need to know and i wasn't aware they ran at a higher pressure than 55 psi.

[Khipset]

Did you test the fuel rail on a 4.2 or find the information somewhere? Google is giving me a bunch of stuff I don't need to know and i wasn't aware they ran at a higher pressure than 55 psi.

Google at some point in time. I thought it was a little high too. Unfortunately I didn't save my sources. I remember searching for the <year> (can't remember that either) TrailBlazer Fuel Pressure and having to go through a bunch hits for fuel pumps. I will see if I can come across some more reliable information.

[SappySE107]

I saw the pumps run up to 60 but that doesn't mean its the fuel pressure. If you find the rating on the regulator let me know.

[Khipset]

I saw the pumps run up to 60 but that doesn't mean its the fuel pressure. If you find the rating on the regulator let me know.

Well, not many sources, but I finally came up with the Part number. FPR is Delphi FP10075, when I searched for it, I have found this site:
FP10075

and Napa

and this GrandAm Forum

Seems the FPR is 61.8PSI