Bad AFR at low boost, correct at full

[sylquebec]

Hi, i have some problem with my AFR.
When my boost is set to the lowest setting(9psi). The car run lean(13-15) at Wide open throttle. But when i set it to 15psi, the AFR look correct around 10.5
I have an apexi neo but there is no setting related to boost.
Anyone can help me?

My setup is: 7mgte,560cc,lexus maf,ct26 57trim,walbro,afpr

 

[ForcedTorque]

First question is WHY if it is so far out at low boost, would you crank up the boost??

Then, on the runs at full boost, is it still lean on the climb to a certain point, and then richens up? You know, like if you are set for 15lbs, are you still lean as you pass 9lbs? Sounds like you could add fuel up to the RPM range where it richens up.

 

[IJ.]

My "guess" would be fuel pressure reg..

 

[Supracentral]

My setup is: 7mgte,560cc,lexus maf,ct26 57trim,walbro,afpr

What kind of AFPR? 1:1 rising rate?

 

[sylquebec]

First question is WHY if it is so far out at low boost, would you crank up the boost??

Then, on the runs at full boost, is it still lean on the climb to a certain point, and then richens up? You know, like if you are set for 15lbs, are you still lean as you pass 9lbs? Sounds like you could add fuel up to the RPM range where it richens up.

1st question answer : I tune my car at 15psi with my neo and my AEM uego wideband. Then realise with setting the boost controler to the minimum the wideband show 14-15 when i'm at wot. It was at first under 10 at 15psi, i lean it a little witn my neo to 10.5. I'm not driving my car really often at wot with the boost set to low...you know?

Second question answer : At 9 psi, it became leaner while climbing RPM.

 

[sylquebec]

My "guess" would be fuel pressure reg..

Could you explain why please? Are you talking about a defective one or a bad setting on it? MY AFPR is set to 30-35 psi at idle.
I bought it from driftmotion : Aeromotive AFPR kit

 

[IJ.]

Could you explain why please? Are you talking about a defective one or a bad setting on it? MY AFPR is set to 30-35 psi at idle.
I bought it from driftmotion : Aeromotive AFPR kit

If the diaphram has a leak it will do what you describe, one thing you didn't mention is the J tube still on the car?

 

[sylquebec]

No more J tube, straight from fuel hard line to afpr then to fuel rail.
Everything from driftmotion
12volt mod for the walbro + no more fuel resistor

 

[IJ.]

I'd try bumping the base pressure to 43psi with the Vacc hose blocked while setting it and see how it behaves.

 

[Turbo Habanero]

One quick question maybe related may not be related but believe it or not i had a similar problem and it was due to a tiny exhaust leak before my wideband sensor.

A exhaust leak before the sensor will sometimes show lean on the gauge.

 

[sylquebec]

Ok so i do more test and i still have that problem.
I tune my NEO to 11.0 AFR for Hi throttle setting. I boost to 16 PSI with a good AFR.
But when i put the boost controller to the minimum, it still super lean. So much lean than when i'm in 4 gear on the highway and i WOT at low boost i see - - on my AEM wideband. Like more lean than the gauge could read. A little scarry... I try upping the fuel pressure but my next step will be to change the AFPR like IJ says...

 

[Dub537h]

*Subscribed to this thread to learn about AFR's and how to tune them*

 

[sylquebec]

Update : I just install my AEM water / meth kit.
It is supposed to richen up by approx. 1.0 :1 but instead of this, its leaning out by .5 :1
I was tune to approx 11.0-11.5 before and i'm know at 11.7-12.0 ??? With the same boost, nothing change.
Could it be related to my first problem of running lean when in low boost? I think there is something strange...

 

[IndigoMKII]

Update : I just install my AEM water / meth kit.
It is supposed to richen up by approx. 1.0 :1 but instead of this, its leaning out by .5 :1
I was tune to approx 11.0-11.5 before and i'm know at 11.7-12.0 ??? With the same boost, nothing change.
Could it be related to my first problem of running lean when in low boost? I think there is something strange...

Flow test your injectors, bet you have some pissing at lower duty..

 

[Backlash2032]

Check for exhaust leaks before the o2 sensor. At that lean you definitely would've melted a piston or 6 by now.

Sent from my HTC Rezound using Tapatalk

 

[sylquebec]

Check for exhaust leaks before the o2 sensor. At that lean you definitely would've melted a piston or 6 by now.

Sent from my HTC Rezound using Tapatalk

Ok, i just finish to helicoil the 2 last hole for the exhaust manifold. There was a small leak i could ear only under the hood when focusing on the exaust manifold. Now there is NO noticable leak to the ear. It doesn't change anything at all. I did not melt anything since i never really push it in low boost. Its like having a geo metro motor in my car. It almost accelerate faster if i don't put the pedal to the floor(I'm talking about low boost setting here) There is a real lack of fuel.
Everything is ok at full boost, except for the water/meth not riching up the AFR... I made 344 whp / 454 lbs at 19 psi 2 weeks ago( before meth)

 

[sylquebec]

Flow test your injectors, bet you have some pissing at lower duty..

explain please, because i dont really see how it could affect the AFR between different level of boost...

 

[Orion ZyGarian]

Some of your injectors might be working just fine, whereas others are under-performing or leaking at 30-40% duty for instance. There's plenty of places you can ship your injectors of to that will "rebuild" them, clean them, and make sure they're all putting out the same and correct amount of fuel. I'm not sure of any by you, but Kirk with the MkIV (some of you might know of him) runs "Boost Lab" locally that does it. I highly recommend this, as anyone that doesnt have new injectors might have crap for injectors.

 

[sylquebec]

If the diaphram has a leak it will do what you describe, one thing you didn't mention is the J tube still on the car?

How to check for a leak? Fuel in the vaccum line? Because there is nothing in it. Fuel pressure climb when i disconnect it. Is the AFPR should retain the fuel pressure after shutting off the car?

 

[sylquebec]

My aeromotive AFPR fall to ZERO 2-3 second after shutting the car off. Isn't suppose to retain the fuel pressure??
I just order a new AFPR and will see what happen. Oh and i read somewhere that using teflon tape is a no no. why?? I did it, thinking it was the way to do it correctly. Teflon could get trap in the fuel system?