Recommendations for EVO Upgrades
Seasoned HDF Member
Joined: Mar 2010
Posts: 21,092
Likes: 7,614
From: Poolville
The dual vs single fire is a topic I dont think Ive ever seen a thread discuss. It would be interesting to hear opinions
even better see some kinda measurable results. I especially miss the sound of Dual fire with Shovelheads
too me it glorifies the Po-Ta-Toe sound just a tad more lol.
My personal reasoning is coil saturation under a load.. Im trying VERY HARD to not let my advice go full race track at every comment lol but its where Ive spent a lot of time doing comparisons because I wanted proof that being said maybe it doesnt matter. My reasoning was when I did lots and lots of passes comparing coils my proof was in what coil would not cut out above 6000rpm under a full throttle load. I would test 2-3 coils of even the same brand and model number. Believe it or not there is always a clear winner. Out of 3-4 one will always consistently shine. Then Id return the others. I use to like the over counter Harley late model softail coils best (1990s) with a Dyna S ignition (still one of the very best ignitions) these days Im buying 3-4 Drag specialties high output single coils and then returning what I deem as inferior. When I compared dual vs single I felt the dual coil itself got hotter and performed less well above 6K after a long day. I felt plug faul increased when using dual. But that was many years ago. And things change. I also dont remember how many duals I used to compare. In truth Im pretty sure it was only a few. I dont remember if I revisited it either.
My personal reasoning is coil saturation under a load.. Im trying VERY HARD to not let my advice go full race track at every comment lol but its where Ive spent a lot of time doing comparisons because I wanted proof that being said maybe it doesnt matter. My reasoning was when I did lots and lots of passes comparing coils my proof was in what coil would not cut out above 6000rpm under a full throttle load. I would test 2-3 coils of even the same brand and model number. Believe it or not there is always a clear winner. Out of 3-4 one will always consistently shine. Then Id return the others. I use to like the over counter Harley late model softail coils best (1990s) with a Dyna S ignition (still one of the very best ignitions) these days Im buying 3-4 Drag specialties high output single coils and then returning what I deem as inferior. When I compared dual vs single I felt the dual coil itself got hotter and performed less well above 6K after a long day. I felt plug faul increased when using dual. But that was many years ago. And things change. I also dont remember how many duals I used to compare. In truth Im pretty sure it was only a few. I dont remember if I revisited it either.
Grand HDF Member
Joined: Sep 2022
Posts: 4,418
Likes: 3,823
From: Florida
yeah, even back in the day with the dealer. Just put it back in the box careful and don’t scratch of mark it. I literally would install carefully make 6 passes and move to the next. With Drag I recently bought 3. I compared all three and exchanged one just telling them it cut out on top.. and it did. Then I compared the replacement with my good one.. my good one was still my good one, so I returned the second for a refund. The last one that I compared was also decent, I kept it as a spare. It’s now on my King and I just ordered two more.. I’ll compare those any stinkers I’ll return and exchange, if they are good I’ll keep them as spares.
Back in the late 90’s early 2000’s I tried Mallory, Accell, Crane.. a bunch. The stock late model (90’s) coils, then the single fire truly outperformed the high dollar ones. Here;s the trick… if you test the high dollar after market they usually made a bigger spark… but then they couldn’t keep up over a load after a few passes. The stock ones I could gap plugs clear up to 55 thou with no break up through the traps… to me that was proof they were better.
It’s not dishonest… if they sell me a product that can;t perform why wouldn’t I return it?
Back in the late 90’s early 2000’s I tried Mallory, Accell, Crane.. a bunch. The stock late model (90’s) coils, then the single fire truly outperformed the high dollar ones. Here;s the trick… if you test the high dollar after market they usually made a bigger spark… but then they couldn’t keep up over a load after a few passes. The stock ones I could gap plugs clear up to 55 thou with no break up through the traps… to me that was proof they were better.
It’s not dishonest… if they sell me a product that can;t perform why wouldn’t I return it?
Last edited by Rains2much; Mar 18, 2026 at 07:55 AM.
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