How do we improve the existing 930’s ignition.
I am thinking the following methods might be worth considering.
MSD, fully programmable:
MSD-6AL-2 Ignition Control - 6421
I suspect can we not only get more ideal timing using a programmable ignition system, MSD offers a unique advantage in that at low rpm its higher intensity and ability to generate multiple sparks will be more effective at burning a lean air-fuel mix that is typical with a boost-enrichment WUR that dose not have acceleration enrichment capability. This is one of the prim advantages of twin-plugging a CIS Turbo.
Thus, it would be a double win!
Because of emissions goals and limitations of using a “weights & springs” mechanical advance with a vacuum canister, we should be able to make improvements in the following areas.
Of idle: We are at about +1 deg at idle jumping to about -8 off idle when we blip the throttle. I suspect we should be closer to -15 at idle and to about -22 by 1500rpm. This should increase throttle response off idle, get us to boost onset faster, and even lower the boost onset point. It will also make for a cooler running motor at idle.
Cruse: If we time our cars to run on US fuel with the stock system we are going to be at about -25 or -26 at curse. Our low compression motors when under the low demand of cruse I suspect can benefit from being at about -36 and read of one built turbo running at -42 on the freeway. This should help efficiency /fuel economy significantly as much or more that 5%. Fortunately, running less than ideal advance at cruse dose not effect the ability to make power.
Boost-Retard: The stock system goes to full retard at about 5 PSI. Thus, it is kind of an all or nothing. This might be less than ideal. If so pulling back boost in a more progressive manner might add some power to the spool part of our operating range. Spool being that point between boost onset and full boost. Further, with the stock 930, Boost-Retard is a fixed position. If one runs .8 bar and wants to jack boost to 1 bar from time to time, one would have to compromise on the side of safety and run less advance at the lower boost level. With a programmable system we can better fit the boost timing to the actual boost level. Additionally, as a motor is more sensitive to detonation near Torque-Peak, a programmable system should allow us to bend the advance curve around TQ peak and thus make more HP later in the rpm range with more ideal advance.
With this system I believe we lock out the existing mechanical advance and set timing to about -16 and eliminate the retard-can. We then use the stock trigger signal and plumb in GM MAP to the intake manifold for load.
Thus, combining fully programmable MSD with CIS could be a powerful combination and improvement.