How PSI drop with FPR in rear
 

Well I bent up one of my SS 1/2" fuel lines today; and it went decent, my first attempt didn't turn out too well. I wasted about 10' of the 20' stick of tubing on the supply line. I really believe that the return line will be much harder to do and snaking side by side with the other line. So I got to thinking' how much fuel pressure could possiblly be lost with my FPR in the rear of the car? I know that it would be better in the front, but I think that it would look alot cleaner and I wouldn't have to run a return line the entire lenth of the car. I was think about running about 12" of line after the pump and putting the FPR on right before the transition to my SS hardline. I know that there are some concerns with doing this; fuel pressure loss due to the lenth of line and various bends from the regulator to the carb. I will have a fuel pressure guage at the fuel log on the carb not at the FPR. Needing someone with when adjusting fuel pressure. Also I realize that the vacumn port will be useless on the FPR if in the rear, but I have seen guys not running them and here is what Malory said about the vacumn port;

"While it is not necessary to connect a hose to the vacuum/
boost compensation port, it may be beneficial in some
cases. The vacuum/boost compensation port can be used
to momentarily decrease fuel pressure (vacuum
compensation) at idle and part throttle, or increase fuel
pressure under blower boost (boost compensation).
Connect a hose between the vacuum/boost compensation
port and a carburetor or intake manifold vacuum port to
vacuum index the regulator. The set pressure of the
regulator decreases about 1 PSI for every 2 inches Hg (2
inches on the vacuum gauge). Connect a hose between the
vacuum/boost compensation port and an intake manifold
boost port to boost index the regulator. The set pressure of
the regulator increases 1 PSI for every 1 PSI of boost".

I guess my main question is could I have enough adjustablity in the FPR to get the desired FP at the carb, and is the vacumn port on the FPR really beneficial? I will be running -8 an soft lines from fuel cell, filter, pump, and then 1/2" hardline length of the frame and switching back to soft lines at the firewall. The fuel pump is a Mallory 140 and has a max psi of 14, the FPR is also a mallory and is adjustable from 3 to 12 psi. Here are specs on the motor;

502 Gen VI 4 bolt main, 9:1 CR
Melling hv oil pump
Crane solid roller p/n 168601 cam .615 .636 246 254 dur @ .050,
crane solid roller lifters
GMPP 12363400 Aluminum Rectangle port heads
GMPP 12361323 1.7 alum Rockers
Edelbrock victor jr 454-R intake
Crank Ext. ballanced, nitriated, crossed drilled gm p/n 10198922
Rods Forged 4340 Steel
Pistons GM P/N 12533507 Forged Aluminum
MSD Pro-Billet Dist.
Holley 850

Sorry for the long post, but I would really like do this if it would work.

Thanks Dustin

you can set the fuel pressure to whatever the regulator allows, whether in front or rear mounted.

Jody

What is the vacuum port used for on a N/A application? Would it very benefial to use?

under vacuum (idle/cruise) it pulls a few psi from the fuel pressure, and then under load when the vacuum drops you get a few psi boost in fuel pressure. It's a common way for the OEM to do it, but I've never done it with aftermarket efi naturally aspirated. It may not work properly with the fpr in the rear of the car due to the line length and possible slow reaction to fuel pressure changes because of the line length.

With forced induction it helps add fuel pressure under boost to compensate for the manifold pressure under boost. Again, with a rear-mounted fpr I didn't run a line but I've always wanted to see if the line length really affects it that much. Everyone talks like it may be an issue, but I've yet to talk to a single person who's actually tried it. As is on mine currently I have 52 psi normally with about 56 psi under boost and/or above 3000 rpms, the increase coming from using the Aeromotive fuel pump controller.

Jody

I would assume that this would also apply to a carb'ed setup

I would not hook the vacuum line to the fpr on a carbed setup, just leave it open to atmosphere.

Jody