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Mix different types of coils

Old Sep 30, 2019 | 05:42 AM
  #1  
manuRx8's Avatar
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From: Asturias
Mix different types of coils

I have finished installing the new MKII coils of Ryan Rotary Performance and the truth is that the sensations are very good, there is an evident improvement in softness and I think that also in acceleration from below.
In addition, in my case it is more significant since before I had OEM coils, type C, in perfect condition and with only 19800 miles, that is, I do not compare them with old or damaged coils.

I changed them in the hope of improving consumption somewhat, although I am very sad to discard the previous coils, since they worked very well and still had a lot of life ahead (they had no white spot, uniform black background)

And this leads me to ask a question:

What do you think about mixing the new MKII coils with the original OEM-Type C?

Since they both share the same Dwell table, I thought it would be reasonable to put the new MKII in the Lead positions and leave the OEMs on the Trail (since they are the auxiliary ones and suffer less).

Has anyone done a test like this?

This would allow me to take advantage of the 2 pairs of OEM coils at least another 20,000 miles (10,000 with each pair) and once those miles were completed, I would put the used MKII in the Trail position and put the unused MKII coils in the Lead position. I think that way I would have coils for life.

The only question would be whether the use of OEM coils in the Trail position would greatly reduce the advantages over using the four MKII.

What is your opinion?

Last edited by manuRx8; Sep 30, 2019 at 05:45 AM.
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Old Sep 30, 2019 | 01:39 PM
  #2  
NotAPreppie's Avatar
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From: 2017 Miata RF Launch Edition
Spark is spark. As long as you're getting enough spark, everything will be fine.

So, the question is... Are you getting enough spark?
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Old Oct 1, 2019 | 02:23 AM
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manuRx8's Avatar
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Originally Posted by NotAPreppie
Spark is spark. As long as you're getting enough spark, everything will be fine.

So, the question is... Are you getting enough spark?
I do not agree with that statement. One of the problems that rotary engines have, derived from the elongated shape of their combustion chamber, is the spread of the flame, that's why they have put 2 spark plugs (and even 3 in some competition engines). Therefore it is not sought to have enough spark, if not "the more the better".

Stock coils with a Dwell of 3.5 ms (at 2000 rpm) and 14V provide 45 mJ of energy and a spark of 1.8 ms. However, the MKII provide 96 mJ of energy and a 2.4 ms spark: I think there is a big difference!

My question was given by the assumption that Trail spark plugs were auxiliary and therefore, even if they were inferior in performance they would not affect much. However, some comments from colleagues in other forums and a more detailed reading of technical documentation have convinced me that I was wrong.

Trail spark plugs, when going more hidden and firing through a smaller hole will always have more difficulty than the Lead to ignite the mixture, so it is interesting that the coils are as powerful as possible.

On the other hand, a failure in the Trail coils would be more difficult to perceive than if this happened in the Lead (since it would affect more consumption than power) so you could be circulating a long time with a bad combustion, without realizing it. Unburned fuel would destroy the cat and therefore the engine.

I think I answered myself, and that is why I am going to leave the four MKII coils, which will guarantee twice the power in the 4 spark plugs.

Last edited by manuRx8; Oct 1, 2019 at 02:28 AM.
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Old Oct 1, 2019 | 08:23 AM
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From: 2017 Miata RF Launch Edition
You're overthinking this.
Spark is spark.

If you have enough spark to get over the activation energy of gasoline combustion, ignition will happen. If you don't, you get misfires.
When the stock coils are working, they provide more than enough energy to make a stock engine run. More energy won't actually help (though it probably won't hurt).

If you're concerned, buy a $20 HEI coil tester and check. If one it bad, you replace it and get on with your life.
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