mats

So it is a feedback loop at idle.

Dave_N

Well, I was talking about the Delco EST distributor (since that is what this thread is about) and, call it "limp mode" if you like, but when running in Distributor Module Mode the engine is running on the Ignition Module's internal advance curve. The timing is not "stuck" anywhere.

What I was suggesting was that base timing is set to achieve proper total advance when running on the Ignition Module's advance curve. Otherwise it might make more sense to use 0 as base.

Dave

mats

Well, going back to the subject, I think that you have a point. But then again you can question why the ignition module has to assume an 8 degree basetiming. It would just be to throw in other numbers in the program. One thing I have thought about is that in the distributor, the gap that has to be jumped by the spark increases with the advance over (and below) the base timing. If the rotor is right in front of the , say, no 1 plug terminal at base timing, it would be 22 crankshaft degrees off at WOT, corresponding to 11 cam/distributor degrees off. If you went for zero base timing it would be 30/2=15 and it quickly becomes quite a gap to jump. If you have a base timing that is somewhere in the middle of the advance dynamic range the distance becomes smaller, otherwise you will need quite an ignition coil to make it. Just a thought

mats

Continuing ón the previous post; 15 cam/distributor degrees would correspond to almost half an inch gap to jump at 30 degrees advance, with zero base timing. If I remember it correctly from school that would take almost 35.000 Volts just to pass that gap, and you still want some Volts left for the plug. I read somewhere that the ignition coil on the 502 MPI delivers some 45.000 Volts, so you would definitely need a more powerful coil to have decent spark at WOT if you were to go for Zero degrees base timing.