Twin-spark ignition is essentially a means of doing away with the distributor cap and the rotor arm.
It should be noted that whilst this is a relatively simple alteration a few points need to be noted to ensure long service.
- IF using the coil off a 126 (or one specified at 1.5 ohms) then the use of the resistor wire (block) is essential.
- IF using a twin coil at around 3 ohms then you Don’t need a resistor wire.
Very useful videos of the coil theory can be found here:
THE CIRCUIT (assuming use of resistor wire)
The circuit wiring for the twin spark ignition system:
- From the Battery
- Through the Ignition switch
- Through the resistive wire
- On to terminal +B on the ignition coil
- Then from terminal –1 on the ignition coil to the distributor body
HOW TO FIT THE IGNITION SYSTEM
- Remove the existing coil, the distributor cap, the rotor arm and existing HT lead set
- IF using a round coil then this will fit the same mounting bolts, if using the square coil then fit as appropriate
- The resistor block needs to be placed in a suitable position, often above and behind the coil. NOTE: On a 126, Fiat fitted it in the bonnet under the opening catch lever!! If you do this then you will have to run the +ve (positive) all the way from the front of the car.
- Connect the old coil +ve wire (Blue) to the resistor and then connect a new wire from the resistor to the +ve terminal on the new coil.
If not using a resistor just connect the blue wire to the +ve terminal in the usual way.
- Connect the old wire (often black) from the distributor body to the –ve (negative) terminal of the new coil
- Connect new HT leads from the coil to the spark plugs
- Note the mechanical points and condenser are still being used.
The contact breaker points should be set at the following settings. Metric 0.47mm to 0.53mm, Imperial 0.018 in to 0.021 in
- Replace the distributor cap with a blank plate that can be purchased OR the existing cap could be used as preferred