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View Full Version : 42# Injectors & 39# FPU



68COUGAR
07-08-2006, 03:52 PM
I'm wondering if I should upgrade to an adjustable FPU. I have 42# injectors & the OEM FPU only goes to 39#'s. What fuel pressure is good, allowing a safe overhead, for 42# injectors? I don't want to lean the Bastard out! How high can an adj. FPU go?

Engine mods: 9" K&N, 80mm MAF, 3.5" air tube, 85mm TB, MP Inlet Plenum, MP II (+20%), Top, DIC w/10" fan, Coy 1 cam, 42# Injectors, Headers, Big Dawg, Flip-Chip, Underdrives, 30# Tensioner Springs.

68COUGAR

(Removed 2nd. MAF, Installed TB. Works MUCH better this way!!!)

XR7inWI
07-08-2006, 10:25 PM
I'm wondering if I should upgrade to an adjustable FPU. I have 42# injectors & the OEM FPU only goes to 39#'s. What fuel pressure is good, allowing a safe overhead, for 42# injectors? How high can an adj. FPU go?

Engine mods: 9" K&N, 80mm MAF, 3.5" air tube, 85mm MAF, MP Inlet Plenum, MP II (+20%), Top, DIC w/10" fan, Coy 1 cam, 42# Injectors, Headers, Big Dawg, Flip-Chip, Underdrives, 30# Tensioner Springs.

68COUGAR

You have TWO MAF METERS ?????? :eek: So what kind of gains did you see with THAT setup? :p

68COUGAR
07-08-2006, 10:46 PM
You have TWO MAF METERS ?????? :eek: So what kind of gains did you see with THAT setup? :p
DOH!!!!!!!!!!!!! My Bad! Thanks for catching it. I guess when I proof read it, I read what I thought I wrote. I've corrected it.

BUT..........................Wouldn't having 2 MAF's & No TB, double the hp & speed created by the 40 lbs of decals on a RICE CAR? I think I'll mention that to some of them next cruise night. LOL.................See how many Ricers DON'T show up next week & can't figure out why their cars won't start! :p

68COUGAR

Mike8675309
07-09-2006, 09:40 PM
The standard way of rating fuel injectors seems to be at 43psi. I'd go with bigger injectors before trying to tweak it too much. The EEc has expectations about how much the injectors will flow for given pulse width. Mucking with it too much will take it out of the self learning ability to adjust.

68COUGAR
07-11-2006, 03:24 AM
The standard way of rating fuel injectors seems to be at 43psi. I'd go with bigger injectors.
These are almost brand new 42#'s. 15 miles on'em!!!
Won't bigger (than 42#'s) injectors REQUIRE an adj. FPR?

68COUGAR

XR7 Dave
07-11-2006, 09:30 AM
No injectors will really require an adjustable fuel pressure regulator. Non Ford injectors will idle a little better and will have about 5% more capacity (at 375hp this means 19hp difference). Keep in mind that on a 5spd car with stock fuel pressure you can make about 375hp without maxing the injectors (320rwhp). Of course this all depends on BSFC so the more efficient the motor is the more HP you'll make before maxxing the injectors. I've seen some AOD cars take 42lb injectors to 100% saturation (not good) at only 320rwhp.

So in your case the real question is, are they Ford injectors or aftermarket?