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Old 05-21-2008, 10:40 PM   #1
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Default COP coil on plug Dwell Question

I am about to install my COP system (Toyota COPs) on my 99 Miata. In reading the various COP threads here I have seen a recommendation for setting dwell at “3.5 ms cranking and 2.5 ms at 12 Volts” and another thread which said that they couldn’t get the COPs to fire "with less than 5.0 ms." My Hydra system has the following dwell values versus system voltage for the stock coil packs:

10.0 V = 7.88 ms
10.3 V = 7.60 ms
10.7 V = 7.16 ms
11.0 V = 6.68 ms
11.3 V = 6.20 ms
11.7 V = 5.76 ms
12.0 V = 5.40 ms
12.3 V = 5.28 ms
12.6 V = 5.24 ms
13.0 V = 5.08 ms
13.3 V = 4.76 ms
13.6 V = 4.52 ms
14.0 V = 4.28 ms
14.3 V = 4.08 ms
14.6 V = 3.92 ms
15.0 V = 3.08 ms

Anyone have a recommended curve for running the COPs and what is the basis for your recommendation. Also, under normal conditions the system is running at about 14.5 V at the ECU.


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Old 05-21-2008, 11:01 PM   #2
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Use 2.5 ms running dwell and see how well it works. The guy running 5.0 ms because it didn't work right otherwise has a unique problem.
We have found the stock miata wiring to be insufficient to power the COPs without a capacitor installed, it seems to help greatly. That is something to consider when installing your COPs.
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Old 05-21-2008, 11:51 PM   #3
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With 6600uf worth of cap between +12 and GND in the COP harness, I'm running with no problems at 12v = 2.5ms, cranking = 3.5ms.

Try it and see. If you get misfires at higher MAPs, then you may need slightly more. If not, you don't.
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