Fuel rail questions?

[EuroDat]

I am too having injector issues so I ordered 6 new injectors and the pallnet fuel rail. Hopefully I'll get the fuel rail in by the end of this week. It was reasonable priced and I can let you know how the fit and finish it. I also noticed how the FPR mounts on the backside and am not quite sure why or how that works.

Most people change over to the FPR from the ZX models. They have one inlet and one oulet and the return piping is routed around the back of the head. You can use the version fron the 280Z, but you will need to block one of the inlets or pipe it back to the CSV. I think Pallnet supplies his rail with a barb between 2 and 3 injectors for the CSV.

Motorsport has both FPR so you can see the difference.

Motorsport! Fuel Pressure Regulators - The Z Store, Nissan-Datsun 240Z-260Z-280Z-280ZX-300ZX(Z31/Z32)-350Z-370Z Parts

There is another member on Hibridz making fuel rails atm going by the name cockerstar.

Chas

[TomoHawk]

FWIW-

I still have the original fuel rail from my 1978 (with "federal" emmisions.) I believe it's in good working condition and it has no leaks.

[mjr45]

I've got a brand new ZX FPR, but was debating using an adjustable one, just for grins and a cleaner look by attaching it directly to the end of the rail. I like pallnet's rail and may look into that if my attempts to DIY don't turn out well. I'll have to take the -6 rail to a machine shop for drilling and tapping since I don't have a drill press, doing it with a hand held drill just doesn't seem like a good idea.

Edited May 5, 2014 by mjr45

[TomoHawk]

What would you expect t happen if you used an adjustable fuel pressure regulator?

[Zed Head]

He said "a cleaner look". And grins.

The cleanest look would be one of the newer ones with a 14mm o-ring port that plug directly in to the fuel rail. I don't think that you can get them in 2.5 bar though (36.3 psi), they're all 3.0 or more.

[EuroDat]

I've got a brand new ZX FPR, but was debating using an adjustable one.

Just to be clear. An adjustable FPR is actually a static pressure regulator. It will maintain a static 36psi across all engine conditions because it doesn't have the vacuum servo to compensate for vacuum in the inlet manifold. Adjustable being in this case, adjusted to a certain static pressure.

The ECU on the other hand is expecting the FPR to adjust fuel pressure to follow the vacuum in the manifold that way maintaining a 36psi pressure difference across the injector tip.

[Zed Head]

Chas-san. You might be thinking of the old Porsche-VW style early adjustable regulators, with no vacuum port. The newer aftermarket regulators have the vacuum port to the back of the diaphragm. They offer an adjustable start-point, but with retention of the vacuum adjustment via the intake manifold. They're typically smooth and racy looking, with a variety of color choices.

Beware the pressure leak-down of the aftermarket regulator though. They are not precision made pieces and the valve seats often won't hold pressure when the fuel pump turns off.

[FastWoman]

What would you expect t happen if you used an adjustable fuel pressure regulator?

With an adjustable regulator of the vacuum compensated variety (e.g. an Aeromotive unit), you would be able to tweak the fuel/air ratio simply by adjusting pressure. However, as already mentioned, these sorts of FPRs leak down after engine shutoff, which would surely worsen the hot restart issue.

[TomoHawk]

Thanks Sarah,

I was referring to the use of the fuel pressure regulator for performance. The only advantage I could think of is to adjust the air-fuel ratio slightly. More pressure would make it richer. If you really need a lot more fuel, bigger injectors would be a better choice. Other than that, I don't think it makes things any more "cleaner" looking than the stock L28 regulator.

Edited May 5, 2014 by TomoHawk

[mjr45]

Tomohawk, Fastwoman and Zed, I already have serious leak down issues which is part of the reason for changing the fuel rail. The injectors are new, but aren't the FJ707's which seems to be the injector of choice. My fuel pressure drops from around 34psi(with vacuum) to around 20 then down to 10 in about 10 minutes, but so far this spring I haven't had any hot start problems. My engine runs very rich as is even with the AFM calibrated, new FPR, CTS, Thermotine, and check valve. I just kinda don't like the FPR mounted on the firewall, but if thats the best place, thats where it will go.

[FastWoman]

Well, mrj45, it doesn't really have to go on the firewall. If you can direct your eyes to siteunseen's photo just prior to his extraordinarily top-heavy fishing companion with the small, golden bandages tied to her body, you'll notice that the return line comes off of a "T" at the back end of the fuel rail. The hose coming off the driver side of the "T" feeds the cold start valve. An alternative configuration might be to have a hose running from the back of the rail to a "T" near the cold start valve. Then mount a FPR to a bracket in that same area, fed from the "T" and emptying to the hardlines that run around the front of the head. If you want to make it neater, put a barb connector into a 7th hole just behind the #6 injector, so that the return hose drops down beside the line of injectors. Then put a plug in the end hole. Better still, figure out some way to bracket a hard, stainless return line in parallel with the fuel rail. There's something seductive about the plumbing of an engine if done neatly.

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And speaking of "clean," Tomo, those hardlines and your FPR look quite fetching! Do they just polish up like that, or are they chromed?

Edited May 6, 2014 by FastWoman

[siteunseen]

http://www.summitracing.com/parts/msd-2222?seid=srese1&gclid=COGdjrL3lr4CFU4R7AodJSAAAw, I think that's what is on the car in the picture. Or this Bosch,http://www.summitracing.com/parts/bch-0280160001/overview/

I had a lot of sleepless nights thinking about this, not really, boost vs. vacuum and how it would work on my car. Never could find a good enough explanation so I went with the single "IN" FPR for the '78s. Zip tyed to the firewall wasn't my end goal but as you can see from my pictures, looking past Billie Jean Dance, once I got it running right with the coolant sensor tweak I haven't even cleaned the engine bay up. Just driving it and enjoying the rides with my dog, it's funny as hell watching her try to anticipate the shifts. When my hand goes to the shifter she leans forward, then I pin her to the seat until 6,000. If I leave the door open just for a second she's in there, and loves it my PETA friends.

After some coffee and my meds kicking in I think it's the Bosch in the picture. It has to be the Bosch, I don't see any vacuum source.

Edited May 6, 2014 by siteunseen