MSD Timing Control; Programmable Timing Computer MSD8981
Timing Computer-Fixed Curve – Part# 8980 -The MSD Timing Computer has a pre-programmed timing curve that eliminates the need for a mechanical advance.
When you start the car, the Timing Computer retards the timing 20° from the set mechanical timing. This provides easy starting and smooth idle. The timing begins to advance when the engine speed reaches 1,000 rpm and continues until 3,000 rpm when the total timing is reached.
The Timing Computer also has a separate high speed retard circuit. This allows you to activate a retard amount via a switch to retard the timing during times of nitrous or high rpm. The retard amount is adjustable with plug-in modules and 2°, 3° and 4° modules are supplied. Page 90 has a full selection of modules and selectors.
Programmable Timing Computer – Part# 8981 – The MSD Programmable Timing Computer has several features in common with the pre-programmed PN 8980 Timing Computer. Both are adjustable for 4, 6 and 8-cylinder operation and both models have a High Speed Retard function.
The difference between the two models is that the PN 8981 Programmable Timing Computer has an adjustable timing curve whereas the PN 8980 is fixed. The Programmable Computer allows you to adjust the start point, rate and total amount of the advance curve to fit your application.
First, the idle or initial timing must be set with the Initial Timing potentiometer. This can be adjusted up to 20° from full advance (total timing). Second, the rpm level where the timing will begin advancing needs to be set. This can be set from 1,000 to 3,000 rpm. The last adjustment is the slope or how fast you want the timing to advance. The range of adjustment for this feature is from 1/2° per 1,000 rpm to 20° per 1,000 rpm. All of these timing adjustments are made with locking potentiometers located on the side of the unit.
