Using ECU to advance / retard timing - physical limitations?

[fordfanboi]

It's been a few years since I messed with my Megasquirt - just moved from CO to TX and need to adjust for elevation. I'm a bit rusty.

I have a Ford 351w based motor and Mallory Unilite dizzy ( IIRC, I'm bypassing the optical sensor ). Since the rotor must line up with each boss on the distributor cap, what problems can I see with having the Unilite modify timing? Is there a way I need to set it up to minimize this potential problem?

I'm having serious overheating problems at idle and there really shouldn't be an issue ( had the same problems in CO ). I have a large aluminum radiator and high flow electric fan and the wideband says I'm idling rich ( 12.8 - 13.0 ). I'm starting to think the timing is retarded and this made me think that maybe my adjustments in the Megasquirt have reached a threshold where they don't do anything. =\

[trakkies]

It can be tricky to phase the rotor arm if you lock the centrifugal advance - more so the more cylinders you have. You could, of course, leave the centrifugal advance active, but trigger from the crankshaft. The distributor then only switching the spark to the correct plug.

[fordfanboi]

Thanks for the reply!

What do I do when the ECU says spark, but the rotor isn't close enough yet and I end up with a shortened spark pulse. Or vice versa where I'm trying to retard timing and the rotor is almost leaving the post and gives it very little spark duration. Or is that period of time so large that I don't need to worry.

Thanks again!

[355vette]

I had a similar problem when I locked out on my BBC. I thought about it and being as there are 8 stators/reluctors and 13 teeth on the dist shaft I figured it might be helpful to move the dist shaft around. I set the motor to 30 BTDC as I reconded that was the mid point of the advance movement and then I started moving the dist shaft one tooth at a time until a reluctor was right on the vr trigger and the rotor was pointing directly to a cap post. I then made that my #1 and put the wires in order from there. Prior to that I couldn't get it to run below 25 degrees advance and the timing mark with a light was erratic. Now I can run as low as 10 degrees advance (dual efi tunnel ram ) and the timing mark is steady. I have my static and my offset at 16 and the megasquirt runs the timing after start. I know some think that wouldn't help but I have now moved on to tuning which I couldn't do before so it might be something for you to think about. To your original question, I think the ECU could move the timing 90 degrees and then it needs to move to the next cylinder.