×

Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Ignition coil assumption of 5A, fuse design

Practical Motorsport Wiring - Club Level

Relevant Module: Practical Wiring Harness Design Skills > Power Supply Design

Forum Posts

Courses

Blog

Tech Articles

Discussion and questions related to the course Practical Motorsport Wiring - Club Level

= Resolved threads

Author
219 Views

Can you explain briefly, how the current drawn by the ignition coils can be considered as 5amps, is not very Cleary from the documentation is mentioning 19A.

And regarding fuses, does the fuses chosen based on the assumption that the current drawn maximum is 5A for ignition coil, so choose 5A fuse

I do not have a coil on my tester at the moment, nor screen captures that I can easily share to show this visually. The 19A (presuming that this is an IGN-1A coil by that draw) is a peak value that the coil ramps up to over the period of the dwell time that has been programmed into the dwell curve in the ECU. This peak is only reached at the end of the charge cycle, and for less than 1millisecond (ms). Over the whole of the dwell time, which depending on the coil in use and the voltage of the system will range between ~1ms and 15ms for older coils, the average current drawn is much lower. When you look at the amount of time that a coil is dwelling for in the entire engine cycle, the average current draw becomes even lower. This is how multiple coils drawing a peak of 19A can be supplied through a 5A fuse without issues.

My coil testing process uses a 5A power supply and a 1K farad capacitor, 22G wiring and a 3mm spark gap. The feed into the coil has a 5A fuse on it that i have never popped, and I have tested hundreds of coils in the last decade plus that I have been doing this. I will run the coil as a single coil on a distributor equipped V8 at 10K RPM for a minute as a test of the calibration, whilst varying the voltage from 8V to 18V, this has never caused the power supply or coil to struggle.

We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?