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I asked because those dwell numbers sound really high for LS2 coils or even stock ones, which I knew he didn't have. High dwell can cause coils to heat up and produce less spark. Mounting them in a hot location can sometimes be a problem, too.
The dwell is high even for the coils or is there some leeway? I have these coils, just not installed since I cannot figure out how to mount them on a VVT cover. So no first hand experience.
(Edit) Copy/Paste from DIY:
Coil specs:
Minimum voltage output (no load, at recommended dwell): 40,000 volts
Output energy: 103 mJ Spark duration: 2.9 ms
Primary resistance: 0.5 ohms (not directly measurable)
Primary inductance: 4.8 mH (not directly measurable)
Secondary resistance: 8,500 ohms
Secondary inductance: 22.5 H
Turns ratio: 71.1
Maximum current: 19 amps
Maximum battery voltage: 17 volts Nominal dwell: 3.0 ms
About the coils. I believe there is some benefit up to 8ms dwell, because of these.
I did reduce the dwell today to 4.5, thinking perhaps overheating as six said. Not sure yet, it's really difficult to reproduce off track. I made changes last week and was like, oh yeah, all good to 315kpa. Nope, pop pop pop down the strip.
As I mentioned to Vlad and Lars, I am just too broke to drop a few grand on my toy car right now. I agree that MS2 is the problem, and it would be nice to make more power on 20psi. But not at this time.
I don't understand -- what about those charts suggests that 8ms is useful for dwell? To me it looks like 3 ms on the first and 2 ms on the second is all there is? Am I missing something?
I have tested the IGN1A's from 1ms to 9ms. Up to 9ms, more dwell = more spark energy delivered to sparkplug. It climbs pretty linear up to 6, then tapers some but still is gaining energy up to 9ms.
I would run the iridiums at .016 gap, bet that fixes your misfire. With 7670/GT45 combo at 35 PSI, 9ms dwell and .015" gap misfired on copper plugs above about 28 PSI. Pulls clean at 35 PSI with the iridiums at .016" and the coils at 6ms dwell. At .020" it misfires terribly.
I'm going to design a CDI Ignition for the car to truly "fix" this at some point. Then I can run .060" gap and all off it no problem. It's on the list, lol.
Ahhh, OK, I understand now. I assumed this was showing the input current to the coil, rather than the output.
If you measure input it winds up looking like this:
We're using a scope to look at current by way of measuring voltage drop across a low value resistor -- I forget exactly how it all works (I'm a software guy, not a EE -- a friend of mine who's more into the electrical side of things was driving this) but the curve flattens out on top and that tells you where it's stopped charging and is just dumping all of the current into heat.
New plugs were better but not perfect. Finally got my elimination skills back though, I would have won semi finals if my friend hadn't cut an almost perfect light. The new Miata runs 14.8.
05-10-2018, 09:34 AM
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