What has the lambda sensor got to do with a 3 wire AFM? It may be called a "lambda" AFM but it's not dependant on the lambda, you could just as well connect to the 3 AFM pins on a 4 wire non-lambda AFM. What has the iacv and cold start got to do with air flow? Without them engine will just be a bit of pain to start and keep running until warm. If you are going racing it's not needed, Sunday and track days only it's not needed, daily driver utter PITA whatever air flow measure you use.
A 3 wire AFM is all you need to measure the air flow. The the Nissan ECU may not like having the TPS removed as the alpha-n signal is used to check the AFM is sensible (fail this check and it goes to limp home mode) but other ECU's are possibly less fussed. AFM = 3 wires.
If you use a map sensor then you are using air density x volume to estimate the air flow. Volume is from engine speed x VE map. Density requires both pressure and temperature. 5 wires.
http://www.lightner.net/obd2guru/IMAP_AFcalc.html
Originally Posted by skyshack
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