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For those who care 77.33 millimeters = 3.04448819 inches. In other words their MAF tapers down to 3" from 3.12".
I hate to say it, but this rules out using a 99+ 540 MAF. They measure 83mm which is 3.268 inches. The software would not be calibrated properly and you'd get a lean condition.

Additional issues this raises:

1) How much effect/benefit is the taper?

2) If you decide to fab up your own Mafs, what inside diameter should you use? 3.044, 3.12 or something in the middle? In other words....

3) What is the inside tubing diameter at the sensor?

Hmmmmm....
 

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I hate to say it, but this rules out using a 99+ 540 MAF. They measure 83mm which is 3.268 inches. The software would not be calibrated properly and you'd get a lean condition.
True, but minor, although you are not getting the most out of the bigger MAF's.

When I added mine, without changing software, my AFR went from 12.2 to 12.5. Not a big deal.
Regards,
Jerry
 

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True, but minor, although you are not getting the most out of the bigger MAF's.

When I added mine, without changing software, my AFR went from 12.2 to 12.5. Not a big deal.
Regards,
Jerry
Ah, real world experience on this...thank you.

Was this with the dinan software that accounts for their MAF or stock-sized maf software?
 

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who cares about the slight taper, i bet that it does little to nothing. plus you can always neck down the piping after the hfm to get the same effect.
 

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True, but minor, although you are not getting the most out of the bigger MAF's.

When I added mine, without changing software, my AFR went from 12.2 to 12.5. Not a big deal.
Regards,
Jerry
Hate to be a jerk about this, but could you post pictures of your AFR?
 

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Ah, real world experience on this...thank you.

Was this with the dinan software that accounts for their MAF or stock-sized maf software?

No, PC software that accounts for the CAI and the headers.:thumbsup:
Regards,
Jerry
 

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Has anyone looked at the size for other cars?

I am sure one of the housings that bosch makes will be closer to the 3.125 to 3 measurement.

I just checked my 2002 discovery series II. The sensor mount is the same, but the MAF is also the same size as the M5's. I am guessing that a V6 car with approximately 250 BHp would have a similar MAF.
 

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I am sure one of the housings that bosch makes will be closer to the 3.125 to 3 measurement.

I just checked my 2002 discovery series II. The sensor mount is the same, but the MAF is also the same size as the M5's. I am guessing that a V6 car with approximately 250 BHp would have a similar MAF.
The MAFs are useless w/o software. From what I remember...the 540i/4.4/4.6 MAF is bigger.
 

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Discussion Starter #98
i installed the 540 ones today and the car wouldnt run right. guess i need software.
So what software are you going to use? And where did you get the 540 MAF housing? I can only find it with the sensor.
 
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