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Old 06-21-2010, 08:13 PM   #1 (permalink)
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Thumbs up dual fire to single fire conversion impressions....

Bike is a 97 FXSTC with decently jetted CV carb, Thunderheader, and Screamin' Eagle high flow air cleaner.

Several months ago I bought a used programmable Screamin' Eagle ignition module and a Screamin' Eagle single fire coil (BOTH for a paltry $100) from a fellow forum member. Until this past Saturday, I had used only the ignition module and held off on converting to the single fire coil setup.

Reason being, I had read almost as many conflicting opinions about this swap, as I have read conflicting motor oil debates, LOL...Just kidding, there's many, MANY more oil debates.

Anyway, finally did the swap to single fire and am glad I did. I'll list the PRO's and CON's for anyone debating this swap.

PRO's:
Seems to start easier
Definitely idles smoother
Seems to rev smoother while riding
Definitely has better throttle response
Decel backfiring that everyone claims was either intake or exhaust leak, is all but gone
Easy swap with just a need to solder three wires.

CON's:
Stock chrome coil cover had to be modified to fit the bigger coil
That's about the only CON I can think of and it was easily rectified with a small angle grinder...
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Last edited by rel3rd; 06-21-2010 at 08:16 PM.
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Old 06-21-2010, 11:13 PM   #2 (permalink)
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motorheads5 is reading this now saying WTF is this?
Interesting thank's for sharing, it seem's like a no brainer after the result's you have experienced
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Old 06-22-2010, 05:04 AM   #3 (permalink)
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I once converted a stroked Shovel and honestly never noticed any difference.Not all motors are created equal.
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Old 06-22-2010, 09:49 AM   #4 (permalink)
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I also converted an Evo to Dynatek single fire and had so much trouble with it that I threw it all in the trash at the shop and had all my stock parts re-installed, so there are both sides of the single fire story.
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Old 06-22-2010, 12:54 PM   #5 (permalink)
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To do a true comparision you would have to run tests in both single and dual fire with the exact same timing and advance curve. Most tuners I have talked to have seen only 1 to 2 horse difference at high rpm, which may be due to coil saturation issues at high rpm.

In theory, if you get a clean burn there is nothing left in the cylinder to burn on the next revolution, so the wasted spark does not pose a problem in most conditions. During cold starting, you could certainly argue that there is not a clean burn and residual air/fuel is there to ignite on the next revolution.

That being said, I do run in single fire mode. Since my daytona twin tech module does both single & dual fire and I already have the single fire coil, why not do single? Whether you run single or dual, the biggest advantage is really having a module that you can set an optimal timing curve for your engine setup.

If you are short on mony and want to use your old factory module as a plug-in backup, buy just a new module, find the right curve and go dual.
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Old 06-22-2010, 01:18 PM   #6 (permalink)
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I've got single fire on both the obsolete EVO and the Shovel.

Both run fine so I'm happy.
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Old 06-22-2010, 02:55 PM   #7 (permalink)
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Smile

Quote:
Originally Posted by dog155 View Post
I once converted a stroked Shovel and honestly never noticed any difference.Not all motors are created equal.
Quote:
Originally Posted by qtrracer View Post
I also converted an Evo to Dynatek single fire and had so much trouble with it that I threw it all in the trash at the shop and had all my stock parts re-installed, so there are both sides of the single fire story.
Quote:
Originally Posted by RidingJerry View Post
I've got single fire on both the obsolete EVO and the Shovel.

Both run fine so I'm happy.
Somehow, I agree with all 3 of you.

Obviously, your results may vary. In my case, I already had everything needed for the swap, already knew the adjustable curve module worked well with the stock coil, and had the spare time to finally do the swap...with good results.


Quote:
Originally Posted by rcsoftail View Post
To do a true comparision you would have to run tests in both single and dual fire with the exact same timing and advance curve. Most tuners I have talked to have seen only 1 to 2 horse difference at high rpm, which may be due to coil saturation issues at high rpm.

In theory, if you get a clean burn there is nothing left in the cylinder to burn on the next revolution, so the wasted spark does not pose a problem in most conditions. During cold starting, you could certainly argue that there is not a clean burn and residual air/fuel is there to ignite on the next revolution.

That being said, I do run in single fire mode. Since my daytona twin tech module does both single & dual fire and I already have the single fire coil, why not do single? Whether you run single or dual, the biggest advantage is really having a module that you can set an optimal timing curve for your engine setup.

If you are short on mony and want to use your old factory module as a plug-in backup, buy just a new module, find the right curve and go dual.
I actually did do a "true comparison" from what you are saying...I already had the adjustable curve module (Curve 1 which is what bike likes), and never touched anything else at all. Just swapped coils, soldered a few wires, and flipped the DIP switch on the back of the module from dual to single fire, then fired it up and put 100 miles behind me.

Like you, I also had the single fire coil, sitting in the shed, and had already spent several hundred miles trying out all of the advance curves built into the module, so why not try it (the single fire coil) and see what results I would get from changing that one item?

Being a crossover from the fast car scene, I'm not one that's concerned about dyno numbers, but more into all around driveability, or in this case...ride-ability.

MY
bike feels much better, all around, so this swap was definitely a positive thing.
I surely understand that some may do this swap and never notice a thing. For that reason alone, I am 100% happy that I bought this setup used for a great price, as opposed to new and "hoping" it worked like it did for me.

Supposedly, and this is just what I have heard & read, the single fire setup tames/helps an aftermarket cam's low rpm/idle characteristics, which I hope to find out soon enough for myself.
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Last edited by rel3rd; 06-22-2010 at 02:57 PM.
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Old 06-22-2010, 09:27 PM   #8 (permalink)
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rel3rd, let me know when you want to do the cam swap. I've got a SE 11 I'll make you a good deal on. I knew you would like the coil, even though it's huge!! The SE cam has 500 miles on it. Look up the specs & shoot me a PM. Glad you finally used the coil.
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Old 06-22-2010, 11:00 PM   #9 (permalink)
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rel3rd, good information! You are right, drivability is what's important.
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Old 06-23-2010, 08:21 AM   #10 (permalink)
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I should have added that my swap was done 35 yrs ago when a very basic single fire was first offered.Not a very good comparison.Both my big inch machines Evo and TwinCam have Single Fire ignitions,it just seems to make sense.
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Old 06-23-2010, 02:05 PM   #11 (permalink)
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Thumbs up

Quote:
Originally Posted by kennyflhr View Post
rel3rd, let me know when you want to do the cam swap. I've got a SE 11 I'll make you a good deal on. I knew you would like the coil, even though it's huge!! The SE cam has 500 miles on it. Look up the specs & shoot me a PM. Glad you finally used the coil.
Thanks Kenny, and sorry I couldn't remember who I got this stuff from. I'll let you know about the cam.
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SuperTrapp SuperMeg, & some duct tape just in case


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Old 06-23-2010, 04:49 PM   #12 (permalink)
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Quote:
I had used only the ignition module and held off on converting to the single fire coil setup.

Reason being, I had read almost as many conflicting opinions about this swap, as I have read conflicting motor oil debates
You do know that single fire ignition works better with Harley Syn 20w-50 in the engine.
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Old 06-24-2010, 05:02 PM   #13 (permalink)
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Quote:
Originally Posted by 1997bagger View Post
You do know that single fire ignition works better with Harley Syn 20w-50 in the engine.
Awwww, CRAP! I have some 15w40 Diesel Oil in it...















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SuperTrapp SuperMeg, & some duct tape just in case


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