Needing advise with tuning

[davenoscott]

I recently put a supercharger on my 91 fox and I'm trying to get it tuned. It's a 331 with a procharger with intercooler. I have 42 lb injectors with a calibrated 76 mm c&l maf. The problem is that it starts off great but at about 4500 or so rpm the A/F ratio goes lean. I checked the voltage on the maf and its about 4.7 Volts at that rpm. Any help would be greatly appreciated. It's getting about 10 lbs of boost at that rpm.

[jestang]

Sounds like you may be pegging the maf though I find that unlikely if you are running a 76 mm C&L calibrated for 42 lb injectors .... which tube do you have in the C&L maf?? ... what fuel pump are you running? What is your fuel pressure at the rpm it starts to go lean? I assume you are running 93? what kind of power are you looking to make? Has your car been tuned?

Edit:
Below is the stock mass air curve in the ecu. You can see in the stock curve, any voltage above 4.76 volts is treated as the same amount of air flow. So unless your car is tuned, the stock ecu is going to try to give the car the same amount of fuel for any voltage above 4.76 even though you are flowing more air and start to go lean. Also the maximum voltage for the maf in the stock tune is 4.9 volts so you are very close to that.

Volts Flow
16.000 857.027
4.768 857.027
4.443 713.186
4.177 611.166
3.886 512.632
3.544 409.345
3.355 356.434
3.149 303.207
2.910 249.663
2.694 206.890
2.582 187.247
2.450 165.386
2.316 146.059
2.154 123.247
1.989 102.653
1.890 92.515
1.803 84.277
1.691 74.772
1.574 64.000
1.468 55.445
1.321 45.940
1.182 37.703
1.091 33.584
.884 24.396
.750 19.327
.571 13.941
.000 13.941

[Silver91Hatch]

First off what are you using to measure your A/F ratio?