R80 electronic ignition issue

[barryh]

Points will work with any coil short of the contacts welding together through switching grossly excessive current. They won't last as long though.

All of the BMW coils intended for electronic ignition have a primary resistance that is no more than half of a points coil therefore the current being switched by the points will be at least double what it should be be so the points contacts are going to suffer.

The other consideration is whether the coil can stand up to sustained primary current without burning out. A points coil will draw approx. 4 amps with the ignition on and engine not running if the points happen to be closed. With a coil designed for electronic ignition that could be 8 amps or more and the coil may not be able to dissipate the heat. This isn't a problem with electronic ignition where some form of dwell control or auto switch off is built in to protect the coil.

[Rob Frankham]

For what it's worth, the stock BMW ignition unit through stock (ish) Bosch (equivalent) coils draws about 4-4.5 volts when the unit is switched on with a line voltage of 12.7 volts. The unit then switches off, less than a second after switch on to protect coils and unit (and battery).

Rob