High Flow MAF revisited - (Porsche 928 voltage MAF)

[David Cooley]

Going on my 3rd week in a hotel here, and browsing thru 1000+ messages so 
I'm a little ogled with all the info... will try my best to stay coherent 
here...



At 09:46 AM 1/16/00 -0800, you wrote:
>Regarding installing a larger MAF sensor. Bruce is right, there is more to
>it than just installing a larger MAF.  The code only recognizes up to 255
>grams/sec.  So even if you get a maf that will read 500 grams/sec the ecm
>won't.  There are probably some people on this list who could write a patch
>to make the ecm recognize 510 grams/sec but I am not one of them and it
>would take a tremendous amount of time.


The MAF doesn't send out a data stream that reads 255g/s  It sends out a 
freq for it's output.
I haven't played with MAF's much, but I would ASSUME that a maf that is 
scaled to 500G/S would have the same max freq as one that is scaled for say 
300G/s.  That being said, the ECM would still think (and fuel accordingly) 
to the old MAF flow values... except instead of 300g/s being maxed out, 
300g/s is being seen in the ECM as say 200g/s.
Same if it's a DC output... they only read 0-5 volts regardless of the max 
flow capability so you have to reprogram the ECM tables to reflect what the 
true flow is at each voltage.


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David Cooley N5XMT Internet: N5XMT at bellsouth.net
Packet: N5XMT at KQ4LO.#INT.NC.USA.NA T.A.P.R. Member #7068
We are Borg... Prepare to be assimilated!
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