SM4 Manual
by
MRM-Racing
V3.0
119
The coil’s charge time determinates from the coil –Ve signal. When the coil switches on,
voltage at the coil negative terminal drops to zero. As the coil charges, the voltage rises
slightly, until a sharp rise where the ignition module current limits. Leaving the coil
switched any longer will not increase the energy in the coil or the spark.
When ignition firing frequency is high, there will not be enough time to charge the coil
completely. After firing the spark, the SM4 will wait a short period and then switch the coil
on again, regaining much of the lost energy in ringing. This break time is normally 0.7 to
1.5 ms long. See figure below
Direct Fire CDI Autronic 500R
The Autronic CDI has four channels; these can be used in any order. To save any confusion
during wiring it is best to keep the CDI input and sequence 1, 2, 3, 4 and the output sequence
the engine firing order.
A good way to do this is to write down the SM4 Ign O/P sequence, CDI trigger I/P and engine
firing order on a piece of paper before wiring.
Example:- 4 cylinder engine four coils with a firing order 1, 3, 4, 2.
SM4 Ign O/P sequence 1, 2, 3, 4
CDI Trigger I/P sequence 1, 2, 3, 4
Ignition coil number 1, 3, 4, 2
Example:- 4 cylinder engine four coils (wasted spark) with a firing order 1, 3, 4, 2.
SM4 Ign O/P sequence 1 2
CDI Trigger I/P sequence 1 2
Ignition coil number 1 & 4 3 & 2
