Running rich....stock FPR along with RRFPR? Need answer ASAP

[MarkEmark]

Hi, my car's been running pretty rich (back fires, stalls under hard braking), at about 8 psi (only in low RPMs, past 4500, its at like 6 psi). Anyway, does the stock FPR need to be run in series with this Bosch 2.5 bar RRFPR I have, and if so, why? We have a 2.2 liter volvo turbo with just a single RRFPR, at about the same boost, fuel injected, MAF setup, and it doesnt have a second one....could this be why it's running so rich?

So basically, do I need the stock one connected or not? I've been running it connected for a while, but when I first ran it at like 6 psi, it wasn't connected at all and ran fine....Need an answer ASAP

[95_240sx]

I run a stock FPR on my car, granted I have 72lb injectors. And if you have the FPR disconnected, your not going to be restricting any fuel i.e. might as well not even run the FPR then. I dont think that for such a low amount of boost youd need a RRFPR.

Rick

[TrunkMonkey]

So basically, do I need the stock one connected or not? I've been running it connected for a while, but when I first ran it at like 6 psi, it wasn't connected at all and ran fine....

are you using an adjustable rrfpr?Quote »I dont think that for such a low amount of boost youd need a RRFPR.[/quote]RRFPRs are pefect for low boost applications. i'd avoid them for high boost because if your not careful, they can create some insane fuel pressures resulting in injectors locking up.

-demetrius

[C-Kwik]

You do need your stock FPR. The RRFPR is not designed to open up flow as you see vacuum and it only restricts return flow under boost.

Running no stock FPR or no FPR at all, will actually result in getting you less fuel to the motor. With the return line wide open, the pressure in the fuel system will drop.

As far as the backfiring and stalling, check for a boost leak. Are you runnong an open of closed loop BOV? Open BOV's and boost leaks will cause what you are desribing.

[MarkEmark]

Ahh...so just from this post, 95_240sx says I probably don't need one, and C-Kwik says I do need one...I'm running rich, and I'm trying to get rid of that problem, I think it's worth a shot to run it w/o the stock FPR. So wouldn't I get less fuel (not run as rich) with just the bosch RRFPR? After all, cars that come turbocharged stock have only one RRFPR...

And no, the one I'm using isn't adjustable...I already checked for boost leaks numerous times...there aren't many places that it can be leaking (I'm only running alc injection right now, the hotside pipe is one piece steel and pretty straight-forward)....I'm not running a true BOV, I'm running a compressor bypass valve...I'm using the one from an Audi TT...it's a closed loop system, it goes from the hot-side pipe and plumbs back into the turbo inlet...no leaks in the the CBV, I already checked it....

I know RRFPR are not the best way to go, but then again, I don't have an unlimited budget, nor do I ever abuse my car. When I drive it to work, I keep it under vacuum for pretty much the whole way, it doesn't see boost more than 50% of the time when I'm driving, and as I said, past 4500 RPM, it's only at like 6 psi (yeah, the turbo isn't exactly matched that well to the engine). Ideally, I'd do 370cc SR injectors, a hacked MAF and a JWT ECU...but if I had that kind of money, I wouldn't be complaining to you all about problems now! Is there a cheap, safe alternative to what I'm doing right now?

Thanks for the input guys...

[:: orion ::]

No experience with RRFPRs here, but...

I would think that wthout the OEM regulator, the RRFPR would hold at your set base pressure all the time, like as if you disconnected the vacuum line to the stock FPR - i.e. under vacuum the stock FPR regulates it to 34psi, and it raises to 43.5 at 0 vacuum or WOT under N/A conditions.

So with just the RRFPR, it's probably running at 43.5psi all the time, vacuum or not (unless you're boosting), so you're getting way too much fuel out of the injectors all the time.

I think C-Kwik would be correct if there were no FPR, but the RRFPR is setting the base (again, should be 43.5) but will only increase under boost, but decrease with vacuum as it should.

So you need to put it back.

Later - Brian

[95_240sx]

Is it running rich and back firing under boost or when in vaccum?

Rick

[MarkEmark]

I never disconnected the OEM FPR, so there's nothing to put back in

I can't tell exactly when it's running rich...but my exhaust confirms that it's rich, as well as the backfiring....I've only noticed it to backfire under vacuum, when I'm braking...and it stalls when I brake too hard....

Arrrr