MAF Clamp Settings


The MAF Clamp function is probably the slickest yet most under-used function in the application.  To illustrate the potential, one of our customers has run a 9-second quarter mile pass on a bone stock 2G DSM MAF using MAF Clamp (previously called Fake MAF for reference).  That's pretty cool.

MAF Clamp is basically a switch over to pseudo speed density just before the point where you might not trust the real MAF signal.   You run on a nice, smooth factory MAF most of the time with a switch over to speed density only when necessary.  The ECU takes care of extrapolating airflow for you based on the VE table you define for your car.  This function can also be useful even when running a GM MAF.  It can help to smooth out the relatively choppy signal produced by a GM MAF under high boost.

A more detailed explanation of how the ECMLink ECU code runs through airflow calculation can be found on the MAF Comp page.  The results of the MAF clamp function can be datalogged as MAFSD.  This is true whether the Enable MAF Clamp function checkbox is checked or not.  The ECU always calculates MAFSD even if it's not going to use it.  This is intended to help dial in the VE table without actually running on the VE table.

To calculate a more customized VE table for your particular setup, first make sure you�re running a boost level low enough to keep MAF Hz below your target clamp point (probably around 2700hz on a 2G or EVO8 MAF and 2100hz on a 1G MAF). Then deselect the Enable MAF Clamp function checkbox, drop the Clamp switchover to a relatively low value like 1500hz, and log both MAFComp and MAFSD. MAFComp is the MAF sensor reading after compensations have been applied to it from the MAF Comp table. MAFSD is MAFComp after VE adjustments have been applied (as well as factoring in pressure if you have Use manifold pressure checkbox selected). Both of these are calculated even when they�re not being used. Adjust the VE table until MAFSD replicates MAFComp.