Runing lean at 37psi fuel pressure. Why?

[DROPthatCLUTCH]

Just installed my AFPR and set the fuel pressure to 37psi with the vacuum line off and plugged. When i put the vacuum line back on it drops about 7 psi.
It's running around 17:1 AFR at 37psi and around 15 at 43psi.

This is with all SAFC settings zero'd out, if that helps at all.. And it's just a stock re-wired fuel pump at the moment, wally should be here this week coming up.

 

[tenn-gsx]

Most injectors are rated at 43 psi. So your running bigger injectors right? If so then this might be why. Considering the car idles at pretty much the correct afr when set to 43 psi. What kind of afpr is it? Do you have a boost gauge to look at vacuum and calculate what your fp drop shoud be when you attach the boost source to the afpr?

 

[pneumo]

The pressure is supposed to drop to around 28 psi when the line is plugged in, not 7psi.

 

[DROPthatCLUTCH]

It is for a 2g..

QUOTE]

You said 2g..That's why I said above 42 psi..

Is it an auto or manual.

Auto 42psi 390cc injectors,manual 36-38psi 450 injectors....

Manual

The pressure is supposed to drop to around 28 psi when the line is plugged in, not 7psi.

Sorry i didn't word that very good. It sits at 37, then drops down 7psi to about 30. I didn't mean that it drops to 7 I'm pretty sure the engine wouldn't be running at that point.

 

[DROPthatCLUTCH]

Just had a thought. When I was threading the gauge in, I was an idiot and spun it in by the gauge itself, rather than using a wrench... It got tough to spin at one point because of the teflon tape and something slipped......
FML So I most likely fkd up the calibration of the gauge. COOL!

 

[DROPthatCLUTCH]

Nope, gauge is fine...
Well I'm confused. Only thing I could think of, is the afpr is restricting fuel or something. Wasn't leaning out at all with stock fpr.
Any ideas guys? Any input is appreciated.

 

[gofer]

Go SET your base fuel pressure to 37psi (vacuum line removed AND plugged) while the car is idling, then push the line back on and it should drop to about 30psi (+/- 1).

If it drops significantly when you reconnect the vacuum line then you need to replace your fuel filter, if it still does it you might be switching to the walbro pump sooner than you thought.

From what it sounds like, it drops 7psi (not TO 7psi) which is what its suppose to do and this thread never needed to exist?

 

[DROPthatCLUTCH]

Yes, it does that. And I'm aware of how to set base fuel pressure. Drops to about 30 psi. But what I'm saying is it's running lean. Between 17 and 18:1 AFR.
Its with stock 450's stock re-wired pump.
If I turn low throttle 1000 rpm setting to +22, then it sits at 14.7:1...
Just seems weird to me... Was running perfect before the AFPR with safc settings zero'd out...

 

[Car Cannibal]

Could be an air leak around the Wideband sensor and it will go really lean like that at idle.

 

[DROPthatCLUTCH]

Ya, could be.. I was thinking of taking my sensor out to recalibrate it anyways, even though I just installed it 2 weekends ago, and drove it once. And it has been working right until after the afpr.
But it still runs lean at higher revs, not just idle.

 

[tenn-gsx]

I would bump it to 42-43 and see how it acts under a load in comparison. Do you have a KNOWN good gauge you can swap? Just because its new and a quality brand does not make it immune to imperfection.

 

[DROPthatCLUTCH]

I did bump it to 43, like I said up there^ and it runs a little bit better, around high 15 AFR.

No I don't have a spare gauge around right now, I could buy one if I really have to but I don't think the gauge is the problem, I took it off, held it with a wrench and tried to spin it to figure out what had slipped earlier, and it was just the face that slid around, no internals were moved whatsoever. And it's reading correct pressure with vacuum disconnected and plugged, and with vacuum hooked up.

 

[tenn-gsx]

OK I didn't realize you drove the car with the fuel pressure bumped up. I thought you were saying you only idled it.
You changed NOTHING else? Just to check. Have you done a BLT and pre turbo post maf check? If you have something leaking before the turbo it will cause you to run lean. Im sure your aware but just reminding ya.

 

[DROPthatCLUTCH]

I didn't drive it, too lean for me. Just held some revs around to see.

Nope, changed nothing else. Had the car running a day or 2 before the installation, installed, then started it up and noticed it was lean.

BLT came out good, just as it was before the install.

Haven't checked for any intake pipe leaks, but don't think thats the problem.. Haven't taken the intake pipe off for a while. I BLT from the LICP.

 

[tenn-gsx]

Well I guess put the stock FPR back on and see if things go back to normal then.

 

[TsiJohn333]

Did you bring your car up to operating temp first or did you just try to set it on a cold start? This might have an effect on your problem.

 

[gofer]

Yes, it does that. And I'm aware of how to set base fuel pressure. Drops to about 30 psi. But what I'm saying is it's running lean. Between 17 and 18:1 AFR.
Its with stock 450's stock re-wired pump.
If I turn low throttle 1000 rpm setting to +22, then it sits at 14.7:1...
Just seems weird to me... Was running perfect before the AFPR with safc settings zero'd out...

Here is what I'm reading.

"I'm running a 16g on stock 450cc injectors and a stock rewired fuel pump and my WB goes lean at WOT."​

The car wasn't going lean before you installed your new afpr because the stock 20 year old fpr was bad so your fuel pressure was high. You installed a working fuel pressure regulator and set it for 37psi base and now its going lean, thats what its supposed to do when you put on a bigger turbo and leave your fuel setup stock. Your SAFC can't ADD fuel to the mix, it can only pull fuel by altering the MAF reading to ECU so you can run bigger injectors. By increasing your base fuel pressure to 43psi you're stretching your injectors even further since they were rated at to 450cc @ 37psi. Keep turning up the fuel pressure and you'll see the same results you did with the stock bad fpr...

Bottom line, get bigger injectors and a bigger fuel pump. Topic RESOLVED, if you've got tuning questions post them in our Tuning/Engine Management forum please.

/CLOSED