Bolt on adjustable FPR

[Digitalwave]

Does anybody know of a good adjustable FPR that bolts to the stock M20 fuel rail, without the need to remotely mount it or change line configurations/types?

[ForcedFirebird]

Why are you trying to adjust pressure? Matching your injector size is a much better option as they are intended to run at a specific pressure. Over-pressurizing your injectors makes them spray "fuzzy" and under-pressurizing them makes them "drip".

Anyways, to answer your question...

https://www.lindseyracing.com/LR/Porsche/944-4037.html

The 944 fuel rail has the same fitting as the e30.

[digger]

Best way to adjust fuel is with injector PW assuming injector DC is ok.

[Digitalwave]

Thanks for the replies. I'm not trying to adjust the pressure actually, I'm looking for an "upgrade" over the stock FPR.

My car holds fuel pressure (car off) when it's cold, but when the motor is hot and I turn it off, fuel pressure drops down to 0psi within less than an hour. It drops 15psi or so in the first 20 minutes alone. The injectors (Bosch GenIII 24#, about 85-88% duty cycle), FPR (Bosch OEM 3.0 bar), and fuel pump (Walbro 190lph inside a Radium surge tank) are all brand new.

There is no fuel in the vacuum line for the FPR. I am going to have the injectors tested this week even though they have ~200 miles on them. This same problem occurred with the [new] stock fuel pump in the stock tank (no surge tank), with another set Bosch GenIII injectors (20#, rebuilt), and with the original FPR. I have since replaced all 3 items, and it's still happening.

The fuel rail is in good shape, and all fuel lines on the car are brand new and none are leaking. Fuel filter is brand new. Even though they are all new, I guess it could be: bad FPR, leaking injector(s), bad check valve on the fuel pump.

The only thing else I can think of is that these injectors don't have the slots for the fuel rail clips, but a lot of people seem to run without them on E30s since the fuel rail holds the injectors to the manifold. I was going to dremel slots into the bodies and put the clips back on just in case they are leaking slightly from the rail, although there is NO evidence of fuel around that area at all.

This behavior doesn't seem normal for E30's based on what I've read, but Supra guys running surge tanks seem to think it's 100% normal. Fuel pressure seems fine when the car is on, and the car is running MS2, which primes the pumps before cranking, so it doesn't create any startup issues.

I'm just stabbing in the dark, I guess

[ForcedFirebird]

Very strange. How is your system wired?

[Digitalwave]

A relay, activated by the stock fuel pump signal wire. More details here: https://www.r3vlimited.com/board/sho...&postcount=187

[ForcedFirebird]

I keep forgetting you are kinda local. I need to get back out to some NASA events. I worked for them for 4years, but haven't been to an event since March of last year.

Since it was happening before the surge tank, I would gather it's the stock side of the fuel system that's causing it. I don't see mention of checking things like the stock fuel relay and/or circuit. I've had corroded relay sockets that caused all kinds of funky things. Worth a check.

Try bypassing the stock fuel relay and see if that helps. I just use a fuse holder and a couple male spade connectors to do a simple "full time on" fuel test.

[Digitalwave]

I was at Sebring with NASA at the end of June. Was wondering, I hadn't seen you out there since Spectoberfest 2 years ago I think.

I guess I should have said, the fuel pressure loss is with the car off, not while running. So the always-on test won't help in this case. But I will clean and test my relay anyways, it's always good to do those sorts of things.

The in-tank pump is a brand new OEM Bosch unit. It could have a bad check valve, but it should have been fixed when I put the surge tank in, since that surge pump is the high pressure pump now (and the stock is just a lift pump).

[ForcedFirebird]

I'll be back ***puts on terminator sun glasses***

[digger]

You can add an extra check valve post fuel pump that will remove the pump as a variable.

Mine kind of does the same, when I turn ignition on the pump runs for a few seconds to prime the system

[e30davie]

what is the issue here? I dont think you'd want fuel under pressure for longer than 30mins?

[Digitalwave]

All the information I've seen is that the stock E30 fuel system should be holding pressure at least overnight. I've never experienced anything remotely close to that.

[Kershaw]

what is the issue here? I dont think you'd want fuel under pressure for longer than 30mins?

If it didn't hold pressure it would take an extra few seconds each time to start the car. Not ideal because you're dumping fuel out of the rail via the injectors and trying to build pressure past that via the pump. The pump can do it, but it would be annoying to deal with the delay each start up.

[Digitalwave]

My Megasquirt primes the pumps when you key on, building pressure before you start cranking. So it has not been a large issue, but it still bothers me knowing it's doing it.

[e30davie]

But it doesn't need to be under pressure, the lines just need to be full of fuel. The lines are probably still full of fuel just sitting at ambient pressure.