FMU Install question regarding stock FPR

[Schmieder]

What thread type is the fuel line running from the bottom of the FPR on a 3100/3400 94-99?

AN6?

I have lots of 3/8" braided steel line rated at 1,000psi so AN6 is preferred. The FMU I am planning on using has barbed fittings that attach to 1/8 npt. Now, running higher pressures I don't trust barbed fittings so I am adapting. If the FPR is AN6 it would make it easy. Then using AN6-1/8NPT adapters for the FMU.

Once I replace the fuel pump I hope to have the braided 3/8" line from the pump>filter>rail. Just an added measure of confidence dealing w/ higher fuel pressures for 5psi turbo.

But I have a feeling the FPR isn't going to make life easy. I haven't taken mine apart to look yet even though the block is stripped down to the heads.

I plan on using an FMU so if anyone has done this before please advise what type of fittings I would need.


I hope the mods don't mind excessive threads? I try to keep new threads to a minimum. At least this way there is a referrence for others. I tried searching for FPR adapter types and found none.

[Weatheralls Auto]

www.wot-tech.com has An6 adapters I believe.

[Weatheralls Auto]

http://wot-tech.com/shop/all/an-6-fittings-for-3x00-fuel-rails/prod_132.html

You will be using 3400 fuel rail ?

[Schmieder]

http://wot-tech.com/shop/all/an-6-fi.../prod_132.html
You will be using 3400 fuel rail ?

The fuel rail is from a 3100. I am under the impression the 3100/3400 are identical except for bore size. Is this correct?

The rail and FPR are stock 3100.

Basically I have a 3100 with 3400 top swap (not on yet) but that is the plan. 3400 heads, LIM, Plenum, TB and slip fit heater hose.

I saw the adapters at WOT but that is before the FPR. I need to know the thread for the bottom line running out of the FPR to the fuel tank. That is where one would mount an FMU?

EDIT:
Now, if the 3100 Fuel Rail will not fit a 3400 LIM/Plenum setup, I just forget about doing a top swap. It would benefit a N/A engine well but I guess going turbo it isn't really going to benefit too much. Am I correct about this assumption?

[ForcedFirebird]

With an FMU you need to keep the stock regulator to maintain your minimum fuel pressure. The FMU goes in the return line and raises the pressure according to boost by pinching off the return after the stock regulator and in turn, the fuel pressure goes up whatever ratio the FMU is (ie 8-1 FMU raises the fuel pressure 8 fuel PSI for every 1 boost guage PSI).

[Schmieder]

With an FMU you need to keep the stock regulator to maintain your minimum fuel pressure. The FMU goes in the return line and raises the pressure according to boost by pinching off the return after the stock regulator and in turn, the fuel pressure goes up whatever ratio the FMU is (ie 8-1 FMU raises the fuel pressure 8 fuel PSI for every 1 boost guage PSI).

Yeah, I figured out the function and the placement in the fuel return line, I just need to figure out what adapter I need to attach to the bottom of the FPR. This way I can have all threaded connections and no barbed/clamped lines.

I would need an AN6 male/female? Or is it AN8? AN10? 1/8NPT, ect.

I'm planning all the adapters I will need. Or most of anyways, I know I'm goign to be making a few trips to advanced auto and my local hardware store.

The fuel lines are going to be steel braided from pump to rail to FPR then FMU. After the FMU it will be stock. Not that I must do this but the fuel line from the filter was damaged removing a rusted filter. I have a rigged connection as of now and holds steady pressure but I won't trust it under increased fuel pressures from the 12:1 FMU.

I guess my question is summed up as...What is the threading for the stock 3100 FPR output?

[FallenZ24]

I ran into this same issue when made custom fuel lines for my fiero. I had a local hydraulic shop cut the lines just after the fpr and braze on a steel male AN fitting. Then I used a female AN fitting and HD rubber hose to make the lines. Braided ss line would be nice but is overkill for my project.

[FallenZ24]

What type of FMU are you using? I have a BEGI (Bell engineering) / Cartech. Rising rate fmu that I used on my first turbo project. I highly reccomend that fmu over the vortech style. The Begi fmu is fully adjustable and not set to one pressure gain ratio (ex. 12:1).

Goodluck with you project.

-Joseph

[Schmieder]

What type of FMU are you using? I have a BEGI (Bell engineering) / Cartech. Rising rate fmu that I used on my first turbo project. I highly reccomend that fmu over the vortech style. The Begi fmu is fully adjustable and not set to one pressure gain ratio (ex. 12:1).

Goodluck with you project.

-Joseph

The fuel line issue, thanks, I had a feeling it was going to lead somewhere like that. At least now I know I need a shop to rig up the lines.

The FMU, that seems like a great idea. I like the option of adjusting the ratio gain.

Thanks man, you hit the nail on the head with that question!

[Schmieder]

What type of FMU are you using? I have a BEGI (Bell engineering) / Cartech. Rising rate fmu that I used on my first turbo project. I highly reccomend that fmu over the vortech style. The Begi fmu is fully adjustable and not set to one pressure gain ratio (ex. 12:1).

Goodluck with you project.

-Joseph

Isn't it possible to use a $20 boost controller to adjust the vacuum/boost line from the manifold to the FMU?

Basically making an Adjustable FMU.

I was reading about Grainger Valves and it appears to be identical to a mechanical boost controller.

Thoughts? Ideas?

[60dgrzbelow0]

If the question is still open about what size threading is involved with GM Schrader/Fuel Line Fitting Sizes...

http://iecoklahoma.com/adapters.aspx

http://www.tamparacing.com/forums/power-adders/126046-turbo-feed-oil-line.html

[Weatheralls Auto]

Correct me if I am wrong, but do the fuel line adapters from WOT-Tech not attach to the bottom of the FPR?
Then allow for AN6 lines?

Schmieder, correct me if I am wrong, is that not what you are wanting to do?

[Schmieder]

Correct me if I am wrong, but do the fuel line adapters from WOT-Tech not attach to the bottom of the FPR?
Then allow for AN6 lines?

Schmieder, correct me if I am wrong, is that not what you are wanting to do?

The WOT adapters are for the fuel rail > -6 AN Male. I know this but they may or may not line up with the return line from the FPR, that I do not know so you may be correct. I can't say for sure.

I was looking for the thread type for the return line connecting the the bottom of the FPR.

But I have found a better alternative, Aeromotives AdjustableFPR for the 3100/3400 GM v6 engines. They can provide an adapter for the AFPR output line in the -6 AN Male fitting. And give adjustability for stock vacuum fuel pressures.


I was looking to use the stock FPR but decided to go adjustable in conjunction with a Vortech 12:1 FMU and a valve bleeder for vacuum line adjustments.

The adapters from WOT would be perfect for a Universal FPR as they allow one to rig a -6 AN fuel line to the rails.

I do have another idea/question.............

If I had the vacuum/boost line from the manifold to the FMU split into 2 lines in the middle, each line having a different rated check valve and vacuum valve, I could adjust the mid boost fuel pressure. So one line with a check valve that opens at 2psi boost and valve bleeder could adjust for mid boost fuel pressure rise rate and the other line could open at 4psi allowing for max fuel pressure boost.

Think such a setup would work? In theory, I could have a check valve for each level of PSI boost, but the combination effect of lines 1+2+3 would be complicated at best.

I am basically trying to work out a cheap mechanic solution to adjust mid boost fuel pressures to avoid over richening at mid boost.

EDIT: This here is really nice but for $360!?! I guess you get what you pay for. I may consider buying it, but the price...ouch.

[FallenZ24]

That super fmu is basicly the same as a begi/cartech unit.

I still have my begi unit somewhere. I'd be willing to sell it if your interested. PM me and we can work out the details if you want it.