Can anyone hazard a guess as to why a resistor is being used in a CDI system?

 

Can anyone hazard a guess as to why a resistor is being used in a CDI system?

It's only a guess and others may soon chime in. My guess is that it's to drain any residule charge in the ignition coil after it fires.

 

My guess is that it is a high value to discharge the capacitor when the circuit is switched off to make it safe to touch.

 

Maybe to damp oscillations?

 

Maybe to damp oscillations?

One full cycle of oscillation is part of the design, so returning any unused energy to the capacitor.

 

It looks like a bleed resistor , to discharge the capacitor when the ignition is turned off, this is a motorcycle ignition.

 

L+C makes resonant tank. Serial resonant tank makes Voltage Multiplication with factor of Q what may stand between 50 and 1000. Then, primary voltage may get close to 10 kilovolts what sure will knock out the thyristor. Thus resistor is diminishing systemic Quality Factor to be safe low.

 

There are a number of possible reasons for that resistor, including most of those already given.
BUT with the rest of the circuit not shown, an accurate analysis is not possible.
An automotive CD ignition system is fairly complex, and consider that the SCR must switch off quite rapidly to avoid damping the oscillations in the coil and to get ready for the next spark, the resistor may be serving a number of purposes. Without the rest of the circuit we can only guess.