Originally posted by bxd20:
DemonSVT, would appreciate your opinion on this.
My first unit had this data:
Set point 650, actual 645.2, set point 450, actual 451.9, set point 200, actual 199.9.
Second unit:
Set point 650, actual 632.1, set point 450, actual 454.4, set point 200, actual 199.3.
(I only gave some data points to keep this short)



Actually the second MAF looks to be calibrated to make the engine run leaner up top, richer in the middle, and the same at lower rpm.
Well at least it appears to be as you only gave half the data required. You did not post any voltage levels for that flow data! Also you don't say if that was from the Meter's function chart or it's calibration chart.

The lower the actual/calibrated flow per the same voltage level the less fuel the PCM commands.

In order to get a real reading on how your MAF was calibrated you would need to post both bench, actual, and voltage and need to post both charts.

There are actually two different information charts on the flow data sheet.
#1 is actual flow vs rated flow.
#2 is rated flow vs calibrated flow.
Both are very important.

For instance my Pro-M's transfer function reads at ~4.7v an actual flow of 847 kg/hr at a 850 kg/hr bench rating. (VERY accurate & efficient - 99.7%) This is the least accurate of any of the useable data points too!

Now the calibration for my Pro-M (which is based off the stock MAF transfer function in the PCM) reads at ~4.7v an calculated flow of 789.4 kg/hr at a 847 kg/hr actual rating. In other words at that specific MAF voltage it is leaning out the mixture vs actual flow about 6.8%.
This is were you make the bulk of your power gains from this mod. It's also why the calibration being off even a hair is such a problem!

This calibration can be and normally is different through the entire MAF voltage range.

If brief my MAF is calibrated through the useable range at -3.1%, -3.7% -5% -6.4% -7.6% -6.8%

Those don't really corelate directly to rpm but a very rough translation would be a 2000 to 8000rpm range.

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.