corkbone

Is this right? i have one on my rx7 with a mallory fpr gauge and it reads out only 3lbs. Do they even make a fuel pump that puts out that much? I need to have at least 6 lbs. with my holley. Or do u guys just think my gauge is wrong?

Project84

The gauge could be wrong. Is the FPR adjustable? What was the fuel pump rated at? Maybe the fuel filter is maxed out on flow volume.

SilverRocket

99% your guage is wrong. FP guages are notoriously innaccurate - I've personally seen 3 different brands (that were supposed to be good) that were all reading a couple psi low at best.

In my experience with my Dellorto at least, you don't need a FP guage to tune - just set the FPR around what you think should be close (ie. turn it up until the carb floods, then back it off; or if it's a 4.5-9psi FPR set it approximately) , and then use a testing trial-and-error method from there to get it dialed.

The guages that I've seen are all hopelessly innacurrate and completely useless for tuning purposes.

corkbone

I wish I would of asked before I went out and wasted $30 on this pos gauge

error402

Welcome, to the club.

-Error402

SilverRocket

Same here - RXcetera and I bought 3 different ones last year before giving up on them. I'm sure it must be *possible* to get a decent one somewhere, but I'm not aware of it. The ones I've seen are absolute toys, nothing else.

I think the problem may actually be that the guages we're buying are 1-15 psi in scale, but we're interested in measuring on the low end of that, which is not as accurate as the midrange. So that if you were running 10 psi or something, maybe the accuracy would be improved, or maybe the guages are calibrated more for that kind of scale. I dunno... maybe if a 1-10 psi guage were available it would be better.

Sterling

What's most important is that the gauge is consistant...which I'm sure it is, though I've never tested any for consistancy.

Do your tuning for the low and mid range, and then jet for the top end according to others' set-ups. Do this with high pressure setting. Then back your pressure down in increments of 1/4 psi. Even if the gauge is inaccurate, 1/4 psi won't be off that much. You're only using it to measure the increments, that's all.

You'll have no change...No change...No change, and then suddenly, you'll start to hit where the fuel level in the carb at high end (high gear, high RPM) is on par with the supply of fuel. Now you're starting to tune.
Keep lowering it in smaller increments, untill you begin to run lean. Then go back a few of those increments. Better to have a slight surplus feeding for inclines, ect. Now you are using the emulsion tubes the way they designed to be used.
You may have to rejet from the very beginning and start all over, but keep the pressure where it's set.

The idea is to have only enough volume of fuel feeding your carb as your engine can ever use at it most consuming time. (Heavey load, high gear, high RPM.) Any more fuel volume than that just keeps your emulsion tubes submerged, and the holes never get exposed to regulate the vacuum signal to the main circuit.
In short, too much pressure = not tuning to your carbs potential.

MarkPerez

I just bought and installed a fuel presure guage the other day. it's a small 1-15 lbs guage . it reads,, or jumps back and forth from 5 lbs to 6 lbs. i don't have a regulator in-line either. The guage cost me $ 10.00 dollors. and $ 5.00 dollors for brass (fittings) I allready have steel braided lines.