Pictures
Here is the circuit diagram (schematic) of aquascooter CDI ignition. Have fun! :-)
First of all lets we see that the bottom side of ignition coil (right side coil) has two functions.
One is that it is the primary coil of ignition transformer (the upper side is the secondary).
Second function is the sensor coil for spark point. Working of the circuit is the following.
The left coil charges the 1uF capacitor to about 150-200V.
At the ignition point the tiristor start to conducts and enables to flow the capacitor charge
to the primary ignition coil. The pulse will be increased by the transformer according to
transmission ratio of the transformer and creates the spark.
The time point of spark is controlled by also the primary coil. Since the gate pin of tiristor
is connected to ground, therfore the tiristor will be switched on when the anode pin of tiristor
has enough negative voltage potential to start to conduct. This potential is due to inducated sinus
voltage of primary coil.
After we have analyzed the circuit it seems for us that this circuit automatic implements the
increased pre-ignition depending on engine rpm. The way how to do this is that the tiristor anode
potential is not only depends on the chrankshaft position but also depends on the rpm, because on
higher rpm the same voltage potential will be reached earlier due to larger amplitude of inducated
voltage. Therefore the spark will be done earlier concerning to chrankshaft position. Briliant! :-)
Homage to designer!
