SE Ignition Modules - Dual and Single Fire

[deejay-2k]

I currently have an SE Ignition module (32655-98) and a dual fire SE coil on my 1993 FLHS.
Once when I throttled hard from a stopped position, I had a 'pop' which to me sounded like a possible detonation problem.
It didn't look like the 32655-98 module had any adjustability, so I purchased the SE Selectable Curve Module (32655-98).
I also liked it because it has an adjustable rev limiter where the 32655-98 module has a scary 8000rpm limit.
The Selectable Curve module also has the capability of using a single fire coil.

Now the questions... 1) Do single fire setups have less detonation problems compared to dual fire setups?
I am questioning whether I should use the dual fire SE coil or purchase a single fire coil.
2) Will the selectable curve module adjusted properly have any advantage(s) over the old module?

deejay-2k

1993 FLHS, 1340 Evo w/ SE Baisley Heads
SE 10.5:1 forged pistons, Woods W6H cam
Mikuni HSR42, SuperTrapp True Dual Slip-ons

[Mike]

The pop could be an acclerator pump issue or incorrect ign. advance for the sudden manifold pressure drop. Your 93 is not equiped with a MAP sensor so the later is hard wired as the VOES toggles between on and off and the two associated ignition tables. Yes the 8k rev limit is scarey and was originally for racing applications where a homologated system was required to meet certain rules.
In theory the single fire system should reduce detonation by reducing the possibility of the motor momentarily backing up on the opposite cylinder firing on the wasted spark while on the exhaust stroke. Another theory says the wasted spark may burn some leftover unburned contaminants in the dead cylinder, reducing these mixing with the incoming charge and thus reducing the chance for detonation (this does not hold much water since SF has lower emissions). In practice we have not seen SF systems to have much affect on detonation when the motor is properly tuned, with correct fuel vs. compression and is in a good state of health (rings, cylinders, carbon buildup, good valve seals, etc.). What the SF system does do is give a little better fuel milage, little better starting, lower emissions and slightly less vibration (the backing up thing). Most of these are so small as to be hard to measure. The selectable curve will allow better optimization of your package from a tuning standpoint. Daytona Twin Tech's web site has a very good explaination of the pros and cons of SF vs wasted spark and their systems are very good. Regards, Mike