Quote:
Originally Posted by YorkshireDave
Question.
Why not fit an aftermarket 'electronic' ignition? Not only do you virtually eradicate points wear as you're only switching low voltage & low current, but the quality of spark is infinitely better across the range and interference is also virtually eliminated too.
Just a thought ...
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If you are referring to the modules such as the Pertronix that just replace the ignition points, be aware that there is a potential down side to these modules. The modules appear to use a darlington pair power transistor to switch the ignition coil primary current. With ignition points, when the points are closed the voltage across the points is close to 0 volts. Because of the use of the darlington pair, when the transistor is switched on (equivalent of points closed) the voltage across the transistor is approximately 2 volts (transistors are imperfect switches). This voltage is called Vce-sat and is a fact of life for bi polar transistors.
The 2 volt drop across the module reduces the voltage available to drive the coil dwell current which generates the spark. If your electrical system is in good shape and the running voltage is around 13.8 - 14.2 volts, the 2 volt reduction in voltage applied to the coil primary will not have a material effect on the spark energy within a B20's normal rev limit of 6000 RPM. However, the 2 volt drop across the module can have a material effect during starting. During cranking of the starter motor (particularly if you have the original non permanent magnet starter) the terminal voltage of the battery will drop from 12 volts to 10 volts (or less). This is further reduced by the decrepitude of the wiring in most vintage Volvos so that the voltage at the coil + terminal can be significantly less than 10 volts during operation of the starter motor. This means that during starting the voltage across the ignition coil can be significantly less than 8 volts. This will have a material effect on the energy of the spark that the coil is able to generate.
If you have to start your car in cold weather and your battery and vehicle wiring are in less than perfect shape the ignition modules will reduce the spark energy potentially making the car harder to start.