I know this has probably been beaten around heaps but anyway.

I have seen many people describe that you want say 25 degrees spark advance at idle for a certain engine. So in the PROM you would have 19 deg at idle RPM + the 6 BTDC = 25degrees. correct?

Or when people speak on here about having so & so much timing at a certain point are they just talking about the pure value in the Main Spark advance or usually spark advance + intial timing?


I also notice that the PROM has a max value of spark advance. Usually around the 41 deg mark. Now the ARAP BIN in the main spark advance has upwards of 45 degrees advance. Does this mean that the ECM will not give more advance because of the limit of 41 set in the constants?

 

Up in the Tuning Guide book sticky, under the '8063/8746/7747 ECMs there is a spark control post. Forget the name, may even state 'spark only ECM' or some such. There is a write up that describes the ins and outs of how the spark timing terms work. It is nearly universal across the range of 3rd gen ECMs.

RBob.

 

Is it called SA Logic? I read the topic and it suggests some changes to make to control the spark better. Really good read.

Thanks,
Mike

 

Yes, that is the one. Some differences: the $6E MAF code doesn't have the SA slope or the warm bias values.

RBob.

 

Sweet I was wondering about those hehehe..