Well, frankly the more I dig into this the more I question the worth of the whole exercise. Here's some stuff I've found that's not really negative but it, as I said, questions the thinking and the functional worth of the functions and capabilities of most aftermarket ignitions. And these guys and their sources aren't selling anything, by the way.
Single fire vs. Dual fire Ignition Systems
http://www.nightrider.com/biketech/hdignitionmodules.htm[The nightrider website ( a great source of info for Evo stuff) won't let me copy directly, but you can read it for yourself. He basically questions the worth of single-fire over dual-fire.]
Here, nightrider specifically praises the SE module, which is what I already have, among several aftermarket units tested:
Screamin’ Eagle ignition modules
http://www.nightrider.com/biketech/hdseignition.htmA quote: “We highly recommend the use of this module on stock and mildly modified bikes. The cost of this module is low and the performance is excellent.”
And fiinally from the book
101 Harley Davidson Performance Projects For Evolution Big Twins and Sportsters I copied these passages verbatim as it explains timing in Evolution engines. It lends credence to keeping the standard advance curves and explains why even aftermarket curves are pretty much the same as stock HD. It also points out the negative side of running hotter timing for extended periods (heat).
“Ignition advance generally starts at some small amount, say 5 to 10 degrees, then increases with engine speed, the idea being that as turbulence in the combustion chamber increase with speed, it affects the amount of time available for burning the fuel-air charge. At some speed, generally 2500-3000 rpm in an Evo engine, this turbulence offsets the burn time.
At that point, the spark advance required becomes nearly constant, up to the highest engine speed.”
“Proper timing helps ensure optimum fuel mileage and a lack of fuel ‘fussiness’ and it’s attendant pinging and dieseling, and last but not least, the engine runs cooler and therefore lasts longer.
It’s almost an axiom that an advance in timing may help power a little, but it will increase heat a whole lot, which is not a great tradeoff in an air-cooled engine. Wouldn’t you trade a tenth or two at the strip for 20,000 more miles on the road?”
“Even aftermarket ignitions with adjustable curves tend to go along with the factory recommendation for maximum ignition timing.”
Another chapter in this same book deals with selecting a high performance factory ignition module. I had no idea that HD made so many over the years--there's a whole chart by part number, advance curve by letter designation and part numbr. I have the Screaming Eagle module 32630-96 with a "P" curve. According to the book "No graph is available for this latest module (formerly HDI). [HDI is HD International]. Harley's position on this is pretty clear from this statement dated 4/16/97: 'That information is considered to be confidential. Although it may have been given out in the past, we have since taken a new position of protectiing that in formation' That said, the new module, fitted to 1996 and newer 1340 models, worked better than the earlier stock module."
I have no idea what to make of the alleged HD refusal to state the curve (EPA trouble maybe?), but the writers seem to believe it works better than stock.
Moving on in the book to the next chapter dealing with aftermarket ignition systems, the author first sums up the stock system and says that the first priority upgrade would be going to a 40,000 volt coil in dual-fire mode. [I've already got a SE 40,000 volt coil.] Reading on, he talks about single-fire:
"The biggest performance advantage to single-fire is probably not the fact that each cylinder gets its own individual spark, so much as the ability to set the timing optimally for each cylinder....easier starting, crisper throttle response.....Whether or not there is a power increase accompanying these benefits is subject to some debate. If there is, you can be it comes from proper ignition timing."
I can set the timing with a strobe and get it dead on the factory mark. Rear cylinder? Who knows? Maybe it varies by a few degrees. Sure does run fine, regardless.
So, to this point, I'm having more and more trouble thinking this project is worth doing, to me anyway. Obviously there are those who are happy with the results and that's fine. But for the the type of cruising I do, with the occasional burst of hot rodding, I just don't see the positives outweighing the cost and the negatives.
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Topic: Aftermarket ignition systems (Read 35566 times)