Fuel Pressure reg for boost

[ForcedFirebird]

OOh ok cool,hmmm what's tha diff inbetween a fpr and a fmu??
witch is the best to use for a boosted car?

FPR regulates the pressure referenced by vacuum, FMU increases pressure in referance to boost. An FMU is usually used when there is no ECM tuning.

[sharkey]

no a fuel pressure regulator regulates fuel pressure, it uses a manifold pressure refference to equalize the fuel pressure so the injectors always working at the same pressure based on manifold pressure. an FMU or RRFPR (rising rate fuel pressure regulator) regulates the fuel pressure 1:1 with manifold vacume, and increases the pressure more than 1:1 under boost. usualy it is used without ecm tuning.

talking with people on the megasquirt forums, most find it best to run a 1:1 fpr, and many perfer a non adjustable or even stock regulator. adjustable regulators and rrfpr often give you to many adjustments to deal with and one slight change can mess everything up.

[ForcedFirebird]

FPR regulates the pressure referenced by vacuum, FMU increases pressure in referance to boost. An FMU is usually used when there is no ECM tuning.

no a fuel pressure regulator regulates fuel pressure, it uses a manifold pressure refference to equalize the fuel pressure so the injectors always working at the same pressure based on manifold pressure. an FMU or RRFPR (rising rate fuel pressure regulator) regulates the fuel pressure 1:1 with manifold vacume, and increases the pressure more than 1:1 under boost. usualy it is used without ecm tuning.

talking with people on the megasquirt forums, most find it best to run a 1:1 fpr, and many perfer a non adjustable or even stock regulator. adjustable regulators and rrfpr often give you to many adjustments to deal with and one slight change can mess everything up.

OK so am I giving wrong information because I said vacuum and not "manifold vacuum"? And since when is there pressure in the manifold in a naturally aspirated engine? So are you trying to say that with a FMU, you can do away with a regulator? I don't see how this would be possible since the diaphrams on the two work in different directions (one increases with vacuum and the other increases with boost pressure).
EDIT: Are you using MegaSquirt? I just ordered my MS1 with spark and knock circuit, so my FMU is for sale.

[sharkey]

technicaly you always have pressure in the manifold, either positive pressure (boost) or negative pressure (vacuume). your description of a regulator was right, i just restated it. i know people that have run fmu's and ditched the regulator. and im going off what ive read and been told with an fmu, i have no first hand experiance with one.

i have been running a megasquirt 2 in my car for 4 months now. its running fuel, ignition, stepper iac, and it is modded for knock retard (programming is there, juts gotta add a resistor and diode to the board) as well as a shift light.

[ForcedFirebird]

Don't want to get too far off subject, but how do you like it? And how was the install (seems pretty easy if you have a wiring diagram of the car).

[sharkey]

i built mine from a kit. it wasnt hard to build, and my install took a day and a half. it wasnt hard to install at all.

[treeZ24]

the biggest part i found when installing the MS was making sure you build the PCB properly having solid solder joints of the components (not cold solder joints) and making sure you get the right polarity of your wires.

for the longest time sharkey was fighting the iac motor, the steps were backwards and then i suggested the wiring was backwards :P. tried that and sure enough it was so changed it around and its great now.

need a laptop as well, suggested with a car charger or inverter

[ForcedFirebird]

the biggest part i found when installing the MS was making sure you build the PCB properly having solid solder joints of the components (not cold solder joints) and making sure you get the right polarity of your wires.

for the longest time sharkey was fighting the iac motor, the steps were backwards and then i suggested the wiring was backwards :P. tried that and sure enough it was so changed it around and its great now.

need a laptop as well, suggested with a car charger or inverter

I have experience soldering (I build/fly electric R/C Helicopters) so polarity and cold joints wouldn't be a problem. I ended up getting an assembled unit from KingEFI and an Innovative WBo2. That's funny you mention the reversed stepper motor, I just read about that on the MS forum. MS1 doesn't support stepper IAC, so I have to mod a selenoid.
I feel bad we are jacking this thread ;p I'll start a new post when I get the MS and/or install the o2 sometime this week.

[SappySE107]

Ok, I am wanting to make a complete kit setup using those lines. I have a 2 line AFPR in mind that I can get the AN-6 fittings for. Would this be an NA type setup and not boost? Do all boost setups work to increase pressure with the regulator or can you go either way? I am not familiar with all the details on boost but I want to offer solutions (or just parts so you can make your own). Are there different rates then? 2:1 4:1 etc?

[ForcedFirebird]

Ok, I am wanting to make a complete kit setup using those lines. I have a 2 line AFPR in mind that I can get the AN-6 fittings for. Would this be an NA type setup and not boost? Do all boost setups work to increase pressure with the regulator or can you go either way? I am not familiar with all the details on boost but I want to offer solutions (or just parts so you can make your own). Are there different rates then? 2:1 4:1 etc?

The FMU RRFPR is just a "band-aid" really. And yes AFPR work in both directions. I have one to lower my fuel pressure so the car will idle with 24# injectors, then the 8:1 Paxton re-raises the pressure referenced off boost. The other way to do it is to leave the stock injectors/regulator and just use the RRFPR (FMU) to increase fuel pressure.
These are both "cheats" though and a lot of people use this method.
I don't know what you mean by "work the other way".
Yes, there are different rates. Most common are 4,8,10:1.
What do you mean a "2 line" AFPR?

[SappySE107]

Both ways meaning vacuum and boost on the same FPR. What does the boost do to the fuel pressure on the stock unit?

2 line meaning send and return. There are different setups available but I want to keep it in/out only.

[ForcedFirebird]

Both ways meaning vacuum and boost on the same FPR. What does the boost do to the fuel pressure on the stock unit?

Nothing, the stock style FPR will only increase pressure under increased vacuum, and vice-versa for a RRFPR. They kind of work hand-in-hand, one works the minimum pressure and the other max pressure (the diaphrams work in opposite directions).

[AaronGTR]

Technically, the FPR is always under pressure whether NA or boosted. Atmospheric pressure is actually 14.7psi at sea level. When the throttle is in a low position you might see below zero on a vacuum gauge, and technically there is vacuum in the manifold because the pressure is less than the outside air, but it is not absolute vacuum. There is still some positive pressure, and when the vac gauge reads zero at WOT you are then at 14.7 psi. The difference with stock regulators is some of them aren't designed to run more than that pressure so they are inaccurate above that because the diaphragm can't handle it. Aftermarket usually have better diaphragms designed for more range. FMU's increase the fuel pressure at more than a 1:1 ratio once they see higher than atmospheric pressure, and as described are just a band aid and no replacement for actual tuning.