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How to use an Oscilloscope to detemine the optimum dwell time

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I get some customers with OEM coils but can't find data on dwell time. I need help on how to use the Oscilloscope to get the optimum dwell time for a particular coil.

I can't get the article from this link http://www.extraefi.co.uk/dwell.htm

This isn't something I've personally done although if you know the rated current for the coil then yes, you can use a scope to measure the required dwell time. The problem is finding the rated current for the coil you're using. Check out the information on this link from Megasquirt:

http://www.useasydocs.com/theory/setdwell.htm

Just use a low amp clamp on either the supply or drive side of the coil. You'll see where the ramp starts to nose over, and can measure from the on point to where it's pretty much saturated. That's the max dwell you should use, as any more than that just goes to heating the coil, and not stored energy. If you were to decide that you only want the coil to reach 5 amps, you would measure from the on point until the current ramp hits 5 amps, and that will be the dwell.

Good article here with a lot of back ground information...

http://dtec.net.au/Ignition%20Coil%20Dwell%20Calibration.htm

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