Another Trigger Offset Question

[obxer]

I'm running wasted spark on an inline 4 cylinder. I'm running dual spark single crank wheel only mode, with a 30-2 wheel, and delay teeth set at 9. (I can easily adjust my trigger wheel relative to the crank - making changes is no problem at all.)

Currently my trigger offset is set at negative 1 in MT. I've read that the trigger offset should be a *large* negative number. When I try changing it to -359, I only get occasional coil firing when cranking - something is definitely not working right - though my cranking RPM shows a good 350 RPM in MT. If I change the offset back to -1.00 it fires right up. Do I need to figure out what is going on here and make adjustments so I have a *large* negative number for offset instead of -1.00? Am I going to have trouble later at higher RPM? I've attached my current msq- maybe there's something I'm missing and I'm compensating with the -1.00 offset?

TIA for responses.

[obxer]

Comments? Anyone?

I need to start working on my spark map but I'd really like to get the offset question figured out first.

[grippo]

The -1 deg setting should work assuming the resulting spark timing on your timing light is where you want it. See the following image to understand what is going on. In dual spark mode the processor sets up to fire spark 2 tach intervals ahead. The figure shows a 2 cylinder, but just substitute 180 deg (15 teeth) bet ween tach pulses for 4 cyl rather than the 360 deg for 2 cyl COP. Since with a -1 deg the tdc is very close to when the tach pulse comes in, then assuming a max advance of 50 deg, you have about 309 deg for dwell.

http://www.microsquirt.info/2cylCOP.gif

[obxer]

Thanks Al!