Discussion
Does anyone know what the average power rating for an ignition coil on a passenger car is???!!!
If not does anyone have any idea where I could find out?
I have some calculations to finish for my degree courswork and it's driving me around the bend!
Thought some of you clever chaps might be able to help.
Cheers
If not does anyone have any idea where I could find out?
I have some calculations to finish for my degree courswork and it's driving me around the bend!
Thought some of you clever chaps might be able to help.
Cheers
Most 12V coils have a DC resistance of about 4 ohms, so they draw a maximum current of 3 amps.
The current must increase from zero to 3 amps in comfortably less than 5 milliseconds to avoid misfires at 6000rpm. This gives an inductance of around 1 millihenry, which at 3 amps gives a stored energy of 9 millijoules. Repeated at 200 times per second this gives a power output of 1.8 watts, ignoring losses.
The system is very inefficient. The input power at this speed is very roughly 18 watts and it gets higher at lower rpm. It also gets higher if you try and get a more powerful spark. Capacitive discharge systems do not suffer from this drawback.
The current must increase from zero to 3 amps in comfortably less than 5 milliseconds to avoid misfires at 6000rpm. This gives an inductance of around 1 millihenry, which at 3 amps gives a stored energy of 9 millijoules. Repeated at 200 times per second this gives a power output of 1.8 watts, ignoring losses.
The system is very inefficient. The input power at this speed is very roughly 18 watts and it gets higher at lower rpm. It also gets higher if you try and get a more powerful spark. Capacitive discharge systems do not suffer from this drawback.
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