Just curious if there is a practical limit of minimum period / maximum frequency that the Ford slot style MAF sensors can report?
The PCM has a "minimum period" setting, but it looks to be mislabeled and really a maximum period / minimum frequency.
Just curious if there is a practical limit of minimum period / maximum frequency that the Ford slot style MAF sensors can report?
The PCM has a "minimum period" setting, but it looks to be mislabeled and really a maximum period / minimum frequency.
it varies depending on the floating voltage and noise threshold of the thermister but lowest ive seen is 79 and highest of 90
A good maf screen should let you get to that lower end.
decipha @ EFIDynoTuning
http://www.efidynotuning.com/
Originally Posted by decipha
Thanks!
The Stock GT500 calibration takes it down to 93. I was curious how much further you could rescale before either losing accuracy or causing an error condition.
on all the digital maf ecus I always take them down to 83 when i simplify the maf points regardless
decipha @ EFIDynoTuning
http://www.efidynotuning.com/
That buys a bunch of headroom. The MAF curve is steep up there!
I looked a bit closer at my MAF rate and period signals, near the top end, and noticed something interesting.
Basically, the slope of the MAF curve near the top does become very important, regardless of whether it is fairly linear and easy to interpolate without much error.
This is because the sensor itself only seems to report integer period values. Because of this, you get a staircase effect. Each of these airflow steps represents ~3% change in flow.
I don't think densifying points in this area would help at all, if the sensor just clicks off integer values. Really, the only way to combat it is to reduce the slope of the transfer function, which would mean getting a larger MAF housing.
MAF REsolution.jpg
I've seen it dip below 80 without a problem. Usually I put the last point 10us lower than my max flow and distribute the points about 5us apart around wot flow. Even though its a steep slope it will let you dial in certain high hp areas without disturbing others.
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