94touring

Its suppose to be about 35-40psi at idle and its a 1:1 regulator, so one psi for every psi of boost.

Lionheart240

Cool. That's what mine is at after re-installing my Vortech FPR correctly. But the problem is that, as soon as I touch the gas it actually fluxuates/bounces between like 36-42psi. Why is it bouncing? Because of that, I have a weird idle sometimes too that likes to rev itself between 1,500 and 1,700.



I'm running 12 psi on balanced/blue-printed primary injectors, and stock secondaries, walboro 255lph fuel-pump, and I've got some random brand fuel-pressure gauge. 12psi on an S5 shortblock with the intake and everything else S4 including the OMP, is that safe to run? My ECU has an FCD programmed into it, and I haven't experienced any fuel-cut yet thanks to it.

RETed

Where is the vacuum source coming from?

Try to place it where the surge plenum is on the intake manifold. The surge plenum is where the vacuum / boost is most stable. It's sometimes very easy to take a vacuum / boost source off one of the runners, but weird resonances can induce weird things like you describe.



I tend to disagree about when the FPR is required. The reason to get an aftermarket FPR is for better control of the fuel pressure. The stock FPR just plain sucks when you increase *fuel pump flow capacity* over 50% over stock - i.e. stock FC turbo fuel pump versus Walbro 255lph fuel pump. If you have a fuel pressure gauge, you can see the fuel rail pressure increase significantly. Now, this is not going to faze most engines, since the rotary engine likes to run rich and fuel computers or stand-alones EMS' can easily compensate for the added fuel rail pressure. I like to require an aftermarket FPR when you start to break the 400hp mark, as this usually requires a full turbo upgrade. Why risk all that money and then skimp on a $200 FPR? Well, with all the lines and fittings in a full blown parallel conversion can easily break $500, but you've spent several THOUSAND by now...





-Ted

Lionheart240

I believe my brother spliced it into where my boost gauge is hooked up.



On the upper intake manifold, right behind the alternator, there are 3 holes. I believe 1 or 2 of them produce boost and vacuum and the other(s) do nothing, my brother has it spliced into there.



It's weird, the fuel-pressure is almost getting more...consistent, when it bounces.



Now it bounces between like 38-42psi, and it seems like it'll eventually just stop bouncing between any numbers. Is the ECU slowly adjusting itself or something? Oh, but now that I'm at 42psi, my gas mileage sucks even more!! YAY!!!



Ugh...

RETed

My rule of thumb...

1) NEVER splice into the FPR vacuum line.

2) NEVER splice into the BOV vacuum line.



Stock FC turbo pressure sensor - **** em, splice that in where ever you want.

The bitch only does ignition retard, and it's not that important - the other two above are.



Yes, the FC turbo front TB has 3 vacuum fittings in a vertical column. Top and bottom most are after the TB - boost and vacuum. The middle one is boost down to 0; it never sees vacuum - this is prior to the TB.





-Ted

IGY

Plain and simple, there is no HP or boost that requires you to change regulators. The one and only factor in whether a different fpr is needed, is volume. The more volume the pump flows the higher the pressure before the fpr. If you are using a higher volume pump, as long as the fuel pressure is within specs you are ok with the stock fpr. If you have a tuneable ECU you can tune for higher fuel pressure.

Lionheart240

But what about the fact that my fuel-pressure actually bounces/fluxuates?



For some reason it seems to be getting more...consistent...less...bouncy, but nonetheless....42psi seems kinda high don't you think?! Jesus, the gas mileage is EVEN worse now because it's running at a higher psi. Before it would bounce between 31-36psi...now it bounces between like 38-42psi and or, it will sit at 40-42psi at idle...come the hell on, this is absurd, for real !

IGY

Is your vacuum at idle bouncing like the fuel pressure? Are you pulling less vacuum now than when you were running lower fuel pressure? Is the pump making funny noises? Pull the vacuum line off the fpr(fuel pressure should go up), and see if the fuel pressure is steady.

Lionheart240

The vacuum will match the revving of the fuel-pressure at idle if it's doing the self-rev from 1,500-1,700. Otherwise the vacuum is like 16 or so if it's idling correctly. The pump is brand new, I know that's not it. We just hooked up my Vortech FPR back up and that's when the fuel-pressure went up from a fluxuation between 31-36psi to a fluxuation between like 38-42psi, and thanks to that, my gas mileage is even worse. LoL



I've noticed though, the fluxuation has become more consistent though. A couple days ago with the FPR installed, it was bouncing between 36-40psi or so, now it's more consistent at the 38-42psi. It idles at like 40psi

IGY

Is the Vortech fpr adjustable? If it has a bolt in the top of the reg with a locknut, all you have to do is losen the locknut and back the bolt out slowly until you get the desired fuel pressure. It is not uncommon for fuel pressure to be different from one fpr to the next.