I don't know what the dwell tables in your Link look like (I understand that they're hard coded in the firmware), but I do have extensive experience with LSx coils. They need more dwell than what a stock Miata ECU commands. I can only ASSUME that a Link (again, ASSUMING FM Miata Link, not something newer like a G3) runs dwell similar to a stock Miata ECU. Therefor, I would conclude that this would not be a good fit.

That being said, I wouldn't suggest going for the type of power that would blow out spark with a Miata Link. I admit I may be biased, but I've also replaced Miata Links and picked up tons of power and drivability.

 

LS coils require longer dwell than you can get with wasted spark at high RPM.

 

Are LS coils not good for wasted spark and stockish redline? I've never known this. I've always planned on upgrading from my Toyota COPs in the far far distant future.

 

Someone doesn't Math very well do they?

With a 8500rpm red line in wasted spark each coil will fire 8500 times a min or 142 times a second. That's every 7 milliseconds. With a 1 millisecond discharge rate you still have 6 milliseconds left for dwell. General rule I have heard is that due to over dwell protection built into the D585 coil you shouldn't dwell them over 4.7 milliseconds. So I see 1.3 milliseconds left.

You could theoretically spin a motor 10,526 RPM with D585 coils in wasted spark. In reality, if you factor in their maximum 80% intermittent duty cycle....you would be more than fine...In the real world....With D585s, in wasted spark, up to 8500rpm.

 

I'm ready for some lsx coils

 

I'd be interested with just the bracket. I already have the LS truck coils. FYI...I don't have a coolant reroute if that matters.

 

What you're missing is that *I* was the one that FM asked to measure dwell on some *actual* LS coils a few years back, and that the required dwell can go > 6 ms.

You will never win at math against me. I work in an engineering group and I'm often the go-to guy for sticky math problems. <evil laugh>

 

I have 3 degrees. One of which is in Mathematics. I used to tutor Engineering students. They were so cute thinking Matrix Algebra was hard.

There are only about 4 different variants of LS coils. The most powerful being the D585s which conversely require the least amount of dwell and are shown to become unstable and over saturated when dwelled longer than 5.5 ms. I run a set of D585s, in wasted spark, on a 11:1 motor with 25 PSI crammed on it and I spin it well beyond the factory reline. I dwell them according to the GM dwell table and run a very healthy spark gap. To say they "require" 6 ms of dwell is simply not accurate.

 

You guys are both right.

I have seen D585 coils that will eat as much dwell as you can give them. I don't think I saved any scope traces, but the coils on my car loved 7 ms of dwell. I've seen others that would trigger themselves while being dwelled somewhere in the 5 or 6 ms range.

I'm sure there are multiple revisions and manufacturers of GM coils. Frankly a coil that fires itself while being dwelled and current limiting is FRAKING STUPID. Save the coil but possibly lose an engine? Engineering at its worst.

Also, there is an elephant in the room that has not been addressed. Dwell is a function of voltage. I want to say that my voltage at coil primary, measured by oscilloscope, was 14VDC. Honestly I set that about 5 years ago and haven't touched or looked at it since.

 

Agreed on stupidity.
The popular Toyota COPs will fire themselves at 80 ms if V>10.5 and 330 ms if V<10.5.
They should have designed them to reduce the current to zero over a millisecond or so instead of firing.
I didn't see that same behavior on the LSx coils FM sent me for testing.

+1 on > 7 ms at low battery voltages for max secondary current, on said coils. Additionally, waste spark may overheat them at continuous high RPM operation, but I didn't test this specifically.

 

FAB9, do you have any updates on this product??