I've tested 5 different brands of d585 coils (8 units per brand) on an oscilloscope, and each had significantly less power and more variance coil-to-coil than used OEM. I would have far preferred to find a good new supplier, but we ended up having to do way more work to source, test and refurbish used ones. Granted I haven't tested NGK, but my understanding is that my experience is common across all brands, and that there are just a couple manufacturers in China producing all the new coils available.

PS, we reject about 5% of used coils because they don't match the typical scope profile. Most of those produce a spark, but are just out of spec from the years of abuse.

Damn, that's a shame.

The fact you're refurbishing used coils I presume means that even brand new GM ones aren't meeting spec? (or at least are cost prohibitive)

They are cost prohibitive from reliable providers ($100+ each) and if you buy from Amazon or eBay there's a very high chance you get a faux-EM.

Back 5 or 6 years ago at least that is about what I found. I tried probably half a dozen different off brand new LS coils. I never found any that worked as well as OEM. So now I just go to the local pick and pull and grab coils off trucks. Generally it costs $50 for a set of 4 with wiring harnesses. I haven't had any issues at all with any from the junk yard.

Looks like we should all just move on to IGN-1A smart coils...

I did and made more power and dont even think about the ignition system anymore.

I mean I have 5+ years on my $50 junkyard set of coils. I am still into my LS coil swap for less then 2 IGN-1A coils. I don't think they are a bad coil, and probably better then the LS coils, but we have always been price sensitive on mt.net.


I am also lazy and don't want to make a bracket for IGN-1A coils.

I made some changes over the winter that would have moved the curve "up" but shouldn't have changed the shape of the curve.....other than a stronger ignition system.. The shape of the curve in the upper range is the result of a strong robust spark replacing one that struggled to ignite the mixture at RPM.

that said, properly set up D585s are making tons of power on a lot of setups...but with new coils being "hit or miss" and used coils being just that.....used wear items.....if you a worried about ultimate reliability, reach out to Ben at DIY and get a set of smart coils and never look back.

https://cimg2.ibsrv.net/gimg/www.mia...ba783b8ba5.jpg