1g MAF Overrun and A/F Ratio? Help...

[talonPOWER58]

Mods:

Boost Control
- TurboSmart Manual Boost Controller set at 18PSI

Intake
- New MHI EVO III Big 16g Turbo
- Front Mount Intercooler w/2.5” Ceramic Coated Short Route Pipes
- Greddy Type RS BOV w/Recirculation Fitting
- 3” Hard Intake Pipe w/K & N Filter

Exhaust
- 3” Turboback Piping to an Apexi N1 Turbo Exhaust (cats removed)
- New EVO III Exhaust Manifold (Unported)
- New 2.5” XS Power o2 External Dump

Fuel
- Walbro 190 lph Fuel Pump
- FIC 650cc Injectors

Tuning
- Pocketlogger Software on a Palm IIIc
- Apexi SAFC NEO
- AEM Wideband

PROBLEM:
My car is tuned pretty well overall, it does run rich at A/F ratio of 10.0:1 from idle to 5.5k rpm. The reason being is it is already at -40 in certain rpm ranges. If I minus out anymore I get additional knock. My problem that I noticed is that after 5,000rpm until redline my A/F ratio will jump from 10.0:1 to 12.0:1 to 17.0:1. As soon as this happens, I let off. My assumption is that it is 1g MAF overrun because my air flow in HZ does not even go up to 1606 HZ and it fluctuates at WOT (I can get some logs up soon). I also noticed that my IPW goes up and down as well at WOT. The end result for now, I lowered my boost to 16psi and my A/F ratio doesn’t go as high but it still goes to 15.0:1. You will also notice I richened up the top end a lot but nothing has helped my air fuel ratio.

My question is this 1g MAF overrun? If so, will purchasing a 3.0” GM MAF and MAF translator eliminate this problem? I really want to utilize the full capacity of my turbo. Any input would be greatly appreciated.

Here is my AFC settings:

RPM 750 1000 1500 2000 2500 3000 3500
Hi Thr -22 -22 -24 -28 -29 -30 -32
Lo Thr -22 -22 -30 -30 -30 -30 -32

4000 4500 5000 5500 6000 6500 7000 7500 8000
-39 -40 -30 +15 +15 +15 +15 +15 0
-38 -40 -30 3 5 3 3 3 0

I usually tune from 3rd gear; however, I noticed that when I go WOT from first gear I get lots of knock between shifts. Anyway to get rid of this?

 

[assault187]

what is your knock level? 10.1.1 @ idle is extremly rich! Where is your front 02, do you have one? You want your AFR's to drop as boost rises. You should site around 14.1 - 16.1at idle and by the time you hit full boost you want to sit around 11.1 - 11.5 for a safe tune.

As far as your dangerously lean AFR's @ high rpm, This happened to me when my FPR boost reference line (vacuum line) popped off the manifold...have you checked this recently? as well as you fuel pressure? Im not familiar with the 1g MAF but if you were to swap it out, why not pick up a 2g maf....cheaper and easier to tune with in my opinion.

 

[talonPOWER58]

sorry at idle my car is at 14.7:1. When I get on WOT it usually stays around 10.0:1, it's hard to lean it out because I have the 650cc injectors and it is already at -40 in certain rpms. I will however check the FPR boost reference line. Thanks for the help. I will let you know. Thanks assault187.

 

[dsm-onster]

I *believe* that your logger won't log hz counts over 1600hz. It's been a while since I've used a logger like that. . .

Regardless. You can be assured that you are overruning your maf. I did w/ similar setup at a similar boost level w/ a small 16g. . . Which performs about the same as an evo3 16g at 18 psi. My maf was hacked to push back overrun.

You'll have to really hack your maf good and TRY to tune it back straight again. Or, you can upgrade to a 2g maf fairly affordably.