what needs to be dissabled from the stock ecu for it to controle only spark withought the airflow meter?

 

disabled ? ALthough I haven't done it, id guess that you'd bypass your injectors on the main harness and run them via the megasquirt. you'll also need to be able to actvate your fuel pump since the fuel pump relay circuit goes through the air flow meter. I'm sure Ken will add anything I've missed.

Sean.

 

I'm fairly certain that the stock MAF provides the load signal to the stock ECU for spark calcs. No MAF = limp mode = fixed timing that will at best get you home. The stock ECU would need dummy injectors (resistors should work) placed on it's injector outputs to keep that from throwing a CEL.

-Mike

 

A few years back (2002??) I ran MS in piggyback mode on an S4. It was basically bone-stock at the time, and I left the AFM in place. I basically unplugged the injectors, wired a resistor across the stock ecu pins to simulate warm engine, and swapped the TPS (added full-span), O2 and CT sensor wires over to MS. It worked fine, and was my daily driver year-round for almost 2 yrs. I did some brief testing with AFM unplugged, and I could notice no difference. Some checking with timing light didn't indicate any timing changes with AFM connected or disconnected. I never went beyond those simple checks, though. If you remove the AFM, you'll need to wire up the fuel pump relay to MS as West-se says, but that's simple enough.

Others have said the stock ecu goes into 'limp-home' mode, retarding timing to some when the AFM is missing. This may be true, but I was never able to validate that claim on my S4.

 

hm... interesting. also, ive been looking at the 1st gen forum and ive notice that they are using some 2nd gen coilpacksa for primary ignition. i was wondering if this could be controled via the megasquirt??
like for example i know that the leadings are ran by the coil packs and the trailing is ran by the distributor. is there a way to read this rpm signal from the distributor, and also be able to controle the leading coils?

 

From all my messing around all these years, I dont think the S4 has a limp mode. I could be wrong though