Adjustable Fuel Pressure Regulator for S4
 

Ok, so my stock FPR is shot. I have on hand an unused adjustable unit with a fuel pressure gauge on it. The plan is to mount my adjustable unit on the firewall and run hoses accordingly. I need a little information before I start tearing things apart, however.

1)Does anyone know what size fitting I will need for the fuel rail? This IS an S4 fuel rail.

2)What is the factory fuel pressure at idle? This isn't super important information, but it will be easier to accomplish this task with it.

3)Has anyone else done this before that already has a write up? I have looked but have not found anything. Yes, I used the search.

There will probably be more questions as I dig into this, but I will address those as I come across them. And if there ISN'T already a write-up, I will make one on how to do this once I'm done, so other people can benefit.

Cheers,
James

This may be a bit of overkill, but take a look.
http://www.fc3spro.com/TECH/MODS/FUEL/fsystem.htm

Fuel pressure is listed in the FSM and it is available electronically at http://foxed.ca/index.php?page=rx7manual

Ah, now that I am back from Formula Drift, I can get back on this. Thank you for the links, by the way.

A little update:
So, I've been busy with one thing after another and haven't actually had the time to start work, but after thinking about it, to get my car back up to speed for the moment, I think what I'm going to do is leave the dead fpr on the fuel rail, and just run hoses to the new aftermarket unit, and then back through the dead fpr. In theory, it will work the same, seeing as the dead fpr is just allowing fuel to be dumped in. Unless someone can come up with a reason that concerns why it won't work, or why I'm putting my life in danger by doing this, this is the plan for when it stops raining. Wish me luck, and another update will follow soon, I hope.

FPR install
 

if your running s4 fuel rails, get the fuel rail adapter on ebay for $18.00 this connectects to your secondary rail on the upper intake manifold, connect the bottom barb on the bottom of your FPR to your fuel return line (driver's side fire wall) then connect the secondary fuel rail opposite your new adapter to either side of your new FPR, adjust fuel presuure as desired... Stock pressure is somewhere around 33-42 psi I believe. I suggest getting AN fittings for your lower fuel rail as well to delete the pulsation dampener which tends to be a source of a great many problems in these cars... fires in particular. good luck.

Ok, so that little tan plastic thing is the pulsation damper? That explains why I couldn't find it under "fuel pressure regulator" at Advance. Lol
I'm not coming up with adaptor, would you mind helping me out with a link? And I'm going to go check in a bit for myself, but do you know off the top of your head what size AN fittings I with need?

BTW, thanks man!

fuel up
 

On Ebay; Type in "RX7 fuel rail adapter"... I know it says it's for FD3S RX7s, but I'm fairly certain it will work on the S4 rail, they both have a slip fitting with o-ring (ask the seller or do some research to be sure it's the same size hole). Also I used 6AN fittings... the primary rail (lower fuel rail) has metric threads on both sides... you may have to special order these adapters (I did), but they are available with 6AN fitting on the other side... then add female 6AN with open barb so you can slide on your fuel line.

You mean this: http://www.ebay.com/itm/FUEL-RAIL-AD...73f26c&vxp=mtr

Yeah, looks like it will indeed work. Thank you again for pointing me towards it.

Now back to the pulsation damper... I must rid myself of this pesky thing.

ebay adapter
 

Hey just wondering did those adapters work on the fuel rail? I too have a non turbo and im doing my fuel hoses now but stuck on the fpr until I found this thread. I just don't want to order that fpr elimination part If it really doesn't fit the fc fuel rail because it's a mm or 2mm bigger because it's an fd / miata / Subaru compatible. Need that help because mazdatrix nor atkinsrotary can give me the O.D. of the fpr inlet, first they were clueless then they don't have the fpr in stock to measure it for me. So does the fc and fd have the same size inlet?

this one works for me, the oring is a tad too large, but still works (last time i pulled it out, the oring was a bit torn, but it still seals). Its nice because it bolts into the stock location, rather than requiring you to thread the fuel rail which is a bit of a risky pain in the ass

i have an N/A 1987

I may be able to shed some light on this topic, as I've recently installed an adjustable FPR on my S4 NA. The best route that I found for plumbing is with AN line. If you're on a budget, standard rubber hoses may be cheaper, but I find AN to look much better.

There are 2 main issues with doing this mod:

1. The stock S4 secondary fuel rail has to be adapted to AN. The side of the rail closest to the firewall is threaded to M14 x 1.5, but the side where the stock FPR is mounted is not threaded at all. You could cut this end of the rail and run a tap through it, or weld an AN bung on there. I didn't find this ideal, as it requires modification to the rail. I went a different route.
Turbosmart offers an adapter to go from the stock fpr fitting, to an NPT female thread. They list it as working for RX7's, but I believe it to be for an FD. The male end of this adapter fits perfectly into out fuel rail, but the holes for the stock hardware to bolt it on are too narrow. This will require you to modify the adapter. I drilled out the holes to a larger size (I believe it was 3/8), and it still would not line up. I took a rat tail file and filed the holes out just enough so that I could thread the original bolts for the fpr into their respective threads. Add that and a little bit of fuel safe RTV, and you've done it. Now you can just get an NPT to AN adapter and finish the plumbing.


2. The second problem is only a problem if you have AC. The AC lines run along the firewall, and don't allow enough room to mount the FPR directly. Also, if you're going to track the car, certain regulations will not allow the FPR to be mounted to the firewall directly. They will require it to be a certain distance away.
If you're keeping the AC lines in place, there's a bracket near the driver side (LHD car) just next to the clutch master cylinder, that acts as a mounting point for part of the AC line, and bolts directly to the firewall. My solution was to fabricate my own bracket that bolted in place of the original, retained the AC line bolt location, and extended out a bit further with a plate at the end to mount the FPR. This is what I ended up doing and it worked well.



If you'd like pictures of anything I'd be happy to provide some.


Also, my fuel setup is as follows:
-Fuel lab adjustable FPR (2 inlet, 1 return)
-walboro 255 fuel pump-radium high pressure fuel filter-stock injectors-stock fuel rails