Sorta botched diy duel feed rail. What now???
 

I have a 99 fuel rail (some of you can probably see where this is headed)

With my lack of understanding about where the fuel entered the rail I assumed it entered through the fpr. I drilled my hole and was happy. I then read that the fuel leaves through the fpr. Son of a bitch! I now how two fuel feeds on the same end of the rail.

Options:

1. continue tapping 99 rail, plug the hole, then tap the top of the rail on the other end and use a 90 degree fitting.

2. modify the fpr so it can be used in line and not attached to the fuel rail. I can probably thread the little nub on the fpr (where the o-ring is) and then attach a female hose barb. Then, I can tap both ends of the rail for supply and use the original supply line as the return with the fpr attached via fuel injection hose.

3. modify a 1.8 rail by doing the usual diy duel feed steps, and cut the in and out hard lines so it will fit on 99 intake.

4. buy a pre-made duel feed

Which seems like the best option at this point?

PLEASE add a note in the diy fuel rail "useful saved post" that the instructiosn are NOT for a 99 rail.

Can we get a pic for those of us that have never seen a '99 rail? I wouldn't suggest #2 though. Tapping and plugging your hole would work, did that with my dual feed hold and it's held fine.

I think I am going with option #1

https://www.miataturbo.net/forum/mem...ms/137/918.jpg


The 90 degree fitting will be between the fpr and the #1 injector feed. If for some reason this location doesn't work. What would be the next best solution?

https://www.miataturbo.net/forum/mem...ms/137/919.jpg

Wow dude. Well, at least you're brave enough to admit what you did around here.

I'd either get another '99 rail and start over or buy an aftermarket dual-feed. Maybe do #3 if doing so isn't jury-rigging it. You want to be especially careful with the fuel system.

if its an aftermarket FPR, then #2 is an option if not, dont waste your time with modifying the stock FPR. The FPR is designed the keep the pressure built up in the fuel rail by basically backing up the fuel line like a dam to the fuel tank, so I doesnt matter if its an aftermarket if you go with number 2, just as long as it keeps the fuel rail pressurized. Here is an example of my aftermarket FPR.

Attachment 199903

So if I understand that fuel rail correctly, it's feed via the hard line that goes along the entire length of the fuel rail, and then the pressure is regulated, but no fuel is returned? You'd need to braze a fitting on to the side for it to work, otherwise I'd be worried that any fitting threaded in directly next to the FPR would block flow to the FPR and hinder its performance. That's why drilling and tapping on the end is the popular choice for the return systems, you're drilling out the entire end plate for a tap, and I believe threading some of the square tubing of the fuel rail, so you'd definitely block the FPR. Man, I can't for the life of me make a coherent post this morning, I need coffee.

Correct, the 99 does not return. the 99 fpr has no outlet line.

I went back out and looked at the location of the fpr relative to the centerline of the rail. I noticed while looking into the rail through the hole that I already drilled that the entrance into the fpr is offset from the rail centerline. The side I plan to tap and the entrance to the fpr appear to be on opposite sides. I feel pretty confident that I will not get obstruction of the fpr. You brought up another concern, and this is a concern of mine now as well. Is the side wall of the fuel rail thick enough to tap and thread?

https://www.miataturbo.net/forum/mem...ms/137/920.jpg

https://www.miataturbo.net/forum/mem...ms/137/921.jpg

Sorry about the less than spectacular image quality.

wow... 99' fuel rails confuse my NA mind... no return lines? wtf voodoo shit is this?! lol
none the less, the rail needs to stay pressurized.

In layman's terms, its pressurized and the fuel stays there until it's used. Instead of the NA systems, which grabs whatever fuel it needs on it's way back to the fuel tank.

No, I don't think the fuel rail is thick enough to create a good thread for sealing, especially at 100psi or whatever it runs at. We worry about our thin oil pans, which are 2-3 times thicker, and those drains supposedly have 0psi going through them.

M-Tuned Miata 94-05 Fuel Rail M-Tuned

:)

Sell it to me for $100 shipped. Call it at dumbass discount.