Erratic timing at idle using MSII/3.0

[agrump]

Greetings,

I have been running MSII/v3 as fuel only for awhile and have decided to add timing control using direct coil control. I have been able to get everything hooked up and get the engine running but I am having a problem at idle speeds. The timing as shown with a timing light is jumping all over the place even though the timing adv signal from MS is rock solid at 12 degrees btdc. As RPM’s increase the timing stops jumping around and matches what MS is sending. I also noticed that the dwell reading from my meter is extremely low at idle but picks up as the rpm’s increase.

I am using a locked distributor with a pertronix ignition module. The pertronix is supplying the tach signal. The logs does not show any spiking, it looks good. Before hooking up the MS ignition stuff, I set the locked distributor up at 10 degrees BTDC, it did not show any erratic behavior with the timing light.

My settings are:

Trigger Offset 11.50
Skip pulses 3
Predictor Algorithm 1st high rpm, 2nd low

Cranking % 50
After start ^% 70
Normal Running % 25

Ign input capture – Falling Edge
Crank trigger – Trigger rise
Coli Charging Scheme – Standard coil charge
Spark Output – going high (inverted)
Max spark duration – 2

Any ideas?

[CantConfirmOrDeny]

Had the same issue with my 914. Take a look at the msq attached to my success story...my timing looks very stable now. Got other things to work on, but stable timing is no longer an issue for me.

What size pullup resistor on your Pertronix? If too small, Pertornix heats up and signal gets weak & noisy. If too large, signal is weak and noisy all the time. It's a very fine line there.

-pmb-