[darkpuppet]

naz,May 18 2004, 08:24 PM Wrote:flofocus.. you said you bought a 70mm MAF.. on that sheet it says they are testing a 65mm MAF... did you double check this? are they saying that the 65mm and 70mm are pretty much the same thing, did someone have fat fingers in data entry, or is this just the wrong sheet?

i'm just speculationg here... but i think for the transfer function you make the assumption that its linear in the range you are using it, so 9 points should be enough to interpolate the rest of the curve

if its easily explainable, could someone pls share the tech of how to go from that flow bench sheet to the transfer function ?

or better yet... title to a book please ?

to use that flow sheet, you would convert the kg/h of air into lbs/min, and the voltage into analog/digital converter 'counts' (multiply the voltage by 205).

Then you enter in the counts with their respective air lbs/min measurements into the MAF transfer function.

The only problem is with only 9 points, you will have to extrapolate the other 21 data points... and while MAFs follow a polynomial function curve, not all the values follow it exactly, so tweaking would be required after the initial tune. (back to the scanner/datalogger).

a sample MAF transfer function (this being the stock SVT MAF I believe) would look like the following:
<a href='http://www.darkpuppet.com/images/maf_transfer.jpg'></a>

note that blue values are less than stock values, and orange are greater than stock. You'll notice towards the bottom that the graphs for different MAFs can cross each other at different points, illustrating that MAF's don't follow a perfect scalar from each other...

you should see the goofiness of some of the old cobra MAFs....

I think it's safest to make sure you have all the datapoints you can get (my 65mm calibrated MAF will come with a 37 point flow sheet), and then go from there with your datalogger.