1071 S wrote:
Quote:
Ignition is about 5 Amps
60 watts ??? seems a lot - am i missing something??
Cheers, Ian
Its not too hard to figure out if the coil Ohms (Rcoil) on the primary winding is anywhere from 0.7 to 3.2 Ohms. Higher ohms for points ignition, and lower for transistorized ignitions.
After that, Icoil=Vdc/Rcoil which will be between 17.4 and 3.5 Amperes because of the differing coil resistances. Most Minis will be at the 3 to 5 amp end as they use a higher Ohm coil because of their points ignitions limitations (points melt with lower ohm coils, like the Bosch GT40R coils for example).
There's a little more to it. The current through the coil pulses with the duty cycle. The coil is charging for around 60 percent of the ignition cycle per plug. So the current will be 60 % of what we have calculated here. However, countering this is Vdc which is actually around 13.7 volts, which increases the actual coil consumptions.
But for all intents and purposes, you can see how we arrive at a rough calculation at 5 Amps(ish).
