The ignition coil cult

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mikenixon
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The ignition coil cult

#1

Post by mikenixon »

There is much that is misunderstood about motorcycle ignition coils, largely because the Internet engenders one-dimensional thinking -- you know, focusing on one thing to the detriment of several other more important things. For example, all the fuss about engine oil brand and weight when the real, critical issues of JASO and maintaining oil level are ignored. Or fuel's ethanol content when other aspects of gasoline are far more important and of more practical concern. We're all like 10 year olds with no attention span, latching onto the first thing to loom large on our consciousnesses, and captive to the powersports media's amusement-park-like preoccupation with the sensational at the cost of the practical. 1

I sigh inwardly each time someone refers to a coil's primary resistance. You should know that no career tech ever measures primary resistance. It's not on his radar. It is immaterial. A coil is not properly tested that way, for one thing, and despite all the buzz about it in aftermarket literature, primary resistance is far from the most important aspect of an ignition coil.

Limiting ourselves to just the conventional ignition coils and not special-purpose or CDI system coils, the coil aftermarket communicates about their products in terms of three different primary resistances: 2-ohm, 3-ohm and 5-ohm. Let's take these in reverse order. The 5-ohm ignition coils are what many vintage points ignition Hondas (CB550, CB750) came with. The 3-ohm coils coincide with later electronic ignition Hondas (CB900). And the 2-ohm coils represent the historic, earliest available motorcycle high performance coils, usually reserved in the literature for points bikes. What is missed in the discussion of coil primary resistances is the fact that any of these three coils can be used in any of the three target bikes with no ill consequence. Mix 'em up, it just doesn't matter. The theory is that higher resistance primaries are to protect the electronic ignitions, and conversely that lower resistance is for points bikes. However, the stock 5-ohm coils on 70s SOHC fours belies this. Similarly, the 2-ohm coils are said to be incompatible with electronic ignitions, yet many have fitted them to DOHC fours with no ill results. Clearly, an ignition coil's primary resistance isn't as important as many think. 2

It is hopefully not a secret that the reason for the different primary resistances in high performance coils is that originally, during the points era, high performance parts companies made only the lower resistance variety, because all that existed were points bikes and points accept higher than stock current levels that the hi-po coils' lower resistance generates with surprising grace. Doesn't phase 'em. The reason the aftermarket coils were lower resistance than stock was that a higher output ignition coil is one with a higher primary to secondary winding turns ratio. It's cheaper and easier to reduce the primary winding count than to increase the secondary, naturally. Then when electronic ignition emerged in the 1980s, high performance coil manufacturers felt they had to hedge their bets and protect these new electronics by leaving the primaries alone and increasing the secondary winding counts instead to get those higher-than-stock turn ratios. Time however has shown that their worries were unfounded.

Much of this I have already written about, but here is one important fact. If your bike is running properly, you have little to gain by going to a high performance ignition coil. Yes, you can widen your plug gap and yes, this has the potential to improve combustion. But the real-world result, especially if you have kept up on your bike's maintenance, is so small you may never notice it. The folks that *do* notice it are those whose bikes suffer from significant tuning deficiencies, and fixing those is what should be done instead and which would net the same result. In a way the high performance ignition coil market, while not causing indifference to proper maintenance, surely has promoted it, "enabling" it as it were, and that is too bad. Misunderstanding prevails. Exhaust all the nuances of the stock tuning before gravitating to modifications that merely cover up your negligence. 3

If you *do* get a noticeable benefit from high output coils -- and you very well might -- do you know what really has happened? Where the benefit comes from? Carburetion. W-what? Yup. While obviously not literally affecting the carburetors, the effect of better ignition does in fact cause fueling to be less critical. Makes carburetion shine. In effect, richens it. Less than perfect carburetion suddenly is super carburetion. Back to that 60/40 rule I dealt with in a previous article. Ignition and carburetion are symbiotic. When either is weak, they both appear weak. Conversely, when one is strong, they both appear strong. Specifically, better spark compensates for imperfect carburetion. And visa-versa: exquisitely dialed-in carburetion makes ignition's role easier, makes fewer demands on it. This is why a thorough engine tune has such great benefit. It is also why all modern bikes now have really wimpy, coil-over-plug ignition coils. You think those coils are stronger than the old type, or even as strong? They're not. They are far lower voltage and get by with that because of their bikes' fuel injection. Fuel injection's superior atomization makes ignition's job much easier. That 60/40 rule again. 4

Focus on the practical. If a points bike, spend 90 percent of your resourses of both time and money on getting the proper superior-quality OEM points assemblies in there, and time them right, and carefully. Check for cracks in the ignition coils. Make all the connections clean and tight. This includes the harness connectors and the engine kill switch, both of which are exposed to the elements on vintage Hondas and which directly and dramatically affect coil voltage. If a later electronic ignition model watch for eventual pulser failure. Confirm a failing pulser by narrowing its air gap. Subsequent improved ignition performance spells the need for pulser replacement. The spark (transistor) boxes also eventually go. Test them by testing around them (pulsers and coils). Make your spark boxes last longer by avoiding starting attempts when the battery is low, which burns out the boxes. As for ignition coils, they actually fail the least often of the three main electronic ignition parts and are easily tested in place without needing tools, not even a meter. Make sure your plug wires are real wire and are tight at both ends, and have no unseen breaks inside the insulation. Change out the resistor caps when they exceed 5K ohms. If you have ignition wiring mods or repairs that include crimp connectors, humble yourself and make that stuff right. Replace your spark plugs frequently.

Don't be a low-performance mechanic. That is, one trying to do so-called high-performance things that actually result in *less* than stock performance. Too many do this and don't realize it. I have had two CBXs in the shop so far this year that were festooned with all sorts of "high performance" add-ons, chrome plating where it wasn't before, and had only a quart of oil in their 5 1/2-quart crankcases. Be a high-performance mechanic. Focus on intelligent, optimum stock performance that will result in high performance outcomes. Make sense?

Notes:
1 I hardly hear from anyone these days when ethanol doesn't come into the conversation, yet these same folks completely ignore cylinder compression, valve adjustment, and correct carburetor tuning.

2 There is also of course the supposed effect of different primary resistances on coil dwell saturation time and other esoteric ignition function considerations. But no one has proved this to be of any practical consequence. More a propeller-head's oscilloscope daydreams than anything, the much-debated primary resistance's effect on coil current eddies and such, thus engine performance, is not something that is noticed in actually riding the machine. No real-world difference is to be detected.

3 I roll my eyes each time I see the phrase "Dyna coils" in a forum member's list of "modifications", or when a customer includes it in the same way in a conversation. The powersports community has "bought the goods" for sure.

4 A high performance ignition coil improves performance -- when it actually does so -- by improving carburetion.
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Re: The ignition coil cult

#2

Post by gltriker »

I just have to Know something, Mike. :oldies

Respectfully, How long does it take you to compose these lectures? ;)
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Re: The ignition coil cult

#3

Post by mikenixon »

Hi, gltriker!

Writing is a hobby. I'm constantly working on twenty or more articles at a time, not just on technical topics but on other areas as well. I probably spend five hours cumulatively on average per technical article, occasionally more. :)
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Re: The ignition coil cult

#4

Post by desertrefugee »

I've said it before that a compilation (and publishing) would be appropriate. It'd be nice to have one nice tidy Nixon package.

Now, about this installment. Another gem. But, I would like to offer up a comment on aftermarket coils. My '78 came to me with a Dyna S ignition and OEM coils. It had a nagging ignition issue (intermittent bucking/spitting/cutting out) that had me stumped. I installed Dyna green coils since it already had Dyna ignition bits. Yeah, any old coils might have worked, but these bolted right up and allowed me to run solid copper core <gasp> automotive wire. Overpriced? Sure. But, for me there's something to be said for plug and play convenience.

Funny thing was that in the course of the install, while removing the ballast resister, I found the likely suspect was a badly frayed wire tying in one side of the resister. Like two strands. Installed the coils anyway as my originals had the ubiquitous cracks on both units.
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Re: The ignition coil cult

#5

Post by Rednaxs60 »

I'm liking these articles. That Mike will take the time to expound on his knowledge and experience is very appreciated. Always nice to have a different opinion/thought on a subject.

As Mike mentions, there is a lot of information available to you and one must put it all together, come up with their own understanding and what works for them.

This is another great article that will fit nicely into my binder of technical articles.

A Bravo Zulu to Mike.

Cheers
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Re: The ignition coil cult

#6

Post by mikenixon »

Thank you desert dweller and red. Much appreciated. I enjoy doing it, hope it shows. :)

Darrell, it sounds like you may have experienced one of the maxims of my world...it is not always the part the fixed the problem but rather often the installation (i.e. the work performed around the part). True in electrical work (your world, I remember) and possibly even more in engine work. For example, big bore installations and camshaft upgrades. More often than not, simply having correct piston clearance dimensions, whatever the bore size, makes all the difference. Same with cams. As I mentioned in a previous article, high performance cams are often attibuted performance gains that actually came from just simply replacing the worn out original.
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Re: The ignition coil cult

#7

Post by 5speed »

desertrefugee wrote:I've said it before that a compilation (and publishing) would be appropriate. It'd be nice to have one nice tidy Nixon package.
I've hinted at it several times as well.. :mrgreen:
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Re: The ignition coil cult

#8

Post by mikenixon »

You guys are very kind.
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Re: The ignition coil cult

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Post by flyday58 »

I think a big part of the aftermarket coil/ electronic ignition/ filter pod scene is driven by people like me: those of us who weren't around these bikes when they were new. When I bought my first CB two years ago at age 60 I basically entered a time warp in reverse: 1981 came to live in 2018. I'm Marty McFly trying to understand the place I ended up in and going to forums for the answers. These guys SOUND like they're authorities so they must be, right? What I REALLY need is a Doc Brown, someone who knows the truth of things and who quietly goes about his business, and doesn't pontificate unless pressed for it. Thanks for being Doc Brown, Mike. Another great article for OUTTATIME guys like me!
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Re: The ignition coil cult

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Post by mikenixon »

:-D
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Re: The ignition coil cult

#11

Post by HOTT »

...More a propeller-head's oscilloscope daydreams than anything...
A quote I will surely use 3 times by this time next week.

"Dyna Green coils..." I still have the set I bought 10yrs. ago in the box, never installed for the '76 (the Condor).
Just did a 1100mi. long weekend recently. Points and all.

Not saying I haven't used after market products on scratch builds. I just don't go looking for "ADD 5% MORE POWER AND CURE MALE PATTERN BALDNESS..." type fixes from a motor that gets it's best performance from a good ol' fashion good tune up. IMHO.


Again thanks Mike you always cut through a lot of smoke. Always enjoy your stuff. action1

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Re: The ignition coil cult

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Post by Chris in TN »

Mike,

Thanks for another good article and one that got my old 2 cycle weed wacker brain going which I suspect is why you write them. I completely agree that adding aftermarket coils expecting better power from an other wise stock and well maintained bike is misguided. So, was I a chump for doing the Dyna S and green Dyna coil mod to my Suzuki GS1000S? I don't think so. What I expected to get from that mod was less maintenance and better reliability than I was getting from the stock points and coils. I would agree that setting points and timing with the stock setup is simple. Yet, that's one maintenance task I haven't even thought of in the last 25 years. As to the coils, the original Suzy coils were starting to suffer from mechanical problems like cracked insulation and broken wires where the connections flexed. Again, replacing them with good after market units is essentially a "fix and forget" solution. Further, with the ignition system sorted I could concentrate on getting the carbs right for the slight mods I did to the bike and that seemed to work out just fine. As you wrote, good ignition lets the carbs shine. So, for me, going to better ignition system components makes sense in a preventive maintenance way. It's sort of like the logic behind double plugging a BMW twin. Horsepower gains? In theory, yes...in reality no, not particularly. The real world benefits are easier starting on cold winter mornings and a bit of a gain in gas mileage. So, as with any contemplated mod, a rider should do their due diligence research to figure out what the real world benefits might be and then either go for it or decide to spend their resources in time and money somewhere else. Their call. Your good article aptly points out that letting the Internet hive mind make that decision for them is foolish.

Thanks again for the fine article.

Chris
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Re: The ignition coil cult

#13

Post by mikenixon »

:)
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Re: The ignition coil cult

#14

Post by Shadowjack »

Sometime in the '70s, Cycle Magazine ran a coil comparison article (I suppose it was written by Phil Schilling). It was a simple test rig with a couple of electrodes on a fixture where they could vary the distance; the greater the gap the spark could jump, the better. They tried various stock motorcycle coils, various "high-performance" motorcycle coils, and just for kicks, a universal automotive replacement they bought from K-Mart for 6 bucks.
All of the MC coils were crap compared to the K-Mart coil. The problem, though, was the K-Mart coil was too big to fit where the MC coils went, you couldn't use it on a dual-lead wasted-spark system, and it drew a huge amount of current. It really just showed how bad the electrical systems were: just enough generation capacity to get the plugs to fire (barely) and run the lights (part of the time) and have some left over to charge the battery (if the lights were off).
Electronic ignition was put on cars because old-style points systems couldn't carry the primary current necessary to ignite the lean fuel mixtures mandated by the government, without eating the points. They also don't degrade like points so emissions would remain at the expected level as the vehicle aged.

Wanna start another discussion? Explain the purpose of a ballast resistor: to protect the coil, or the points?
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Re: The ignition coil cult

#15

Post by mikenixon »

Appreciate the comment. I hope we can disagree amicably, but I'm afraid I *have* to disagree with several points you've made. I am familiar with that (3- or 4- part) article series also. (I can still see in my mind's eye the RD350 with the big 'ol coils hanging off the front of the frame.) By "crap" I suppose you're referring to the fact that bike coils could not be loaded down and still fire as much as the oil-filled canister type car coil could. While the length of a test gap is a decent indicator of strength, voltage is not directly proportional to performance. There are other variables, and I have explained those in earlier posts. Beyond the voltage needed under the most extreme conditions, plus the surplus that ensures a good margin, more is superfluous. Magic sparks is a myth.

The point I have made in this article and in several others is that the bikes they used in the experiment, and any bike that gets a simple higher than stock ignition coil installed on it, ran/run better because they effectively carbureted better, the coils compensated for carburetion shortcomings (carburetors by definition are compromises, and then add real issues and carburetion can ultimately always be improved), not because the car coils' overcame any ignition deficiency. I don't at all consider OEM Honda point or TPI (electronic) ignitions to be marginal performers. Given components in good health, these ignitions actually work quite well in their intended environment, even when stressed by certain special adjustments geared toward performance (such as high dwell settings on points systems and larger than normal plug gaps on either type). Don't forget that the first season of Honda's 1025 superbikes used completely stock ignition systems, and that back in the day these were new bikes and when magazines put them through the ringer, ignition shortcomings were not heard about. They did not exist.

It is a common theme on some vintage Honda forums that the electrical systems on these bikes are marginal. Seems to be a favorite bogeyman of many. I have preached against this fallacy for many years now. Granted, 240 watts is virtually nothing compared with the over 1000 watts available on many bikes today, but no one stops to think that it was unheard of for anyone to complain about batteries going dead in those days. Yet, today, we have people on forums telling others, "better not put a quartz headlight on your 550, it'll drain the battery", and "it's normal for old Hondas to run their batteries down while riding in town." What nonsense! What utter and complete foolishness! As if some physics laws had changed over the last 40+ years. I am really not interested in trying very hard, but if I had to come up with reasons folks genuinely think these things, I would offer the following. First, really crappy (quality) batteries. A ton of these out there. No one seems to realize how very poor quality low-priced motorcycle batteries can be. Second, equally crappy aftermarket charging system replacement parts. A load of this stuff too, and most forum folks seem to not think twice about using Taiwanese stators and field coils, or of modifying or substituting parts whose function they don't even understand. Third, all 40+ year old bikes suffer from the neglect of their electrical connectors, and this undoubtedly takes its toll on electrical system performance, don't doubt it. Fourth and possibly most significant, there is a riding ethic today among the owners of vintage Hondas that would be totally foreign to those of us who owned these bikes in the 70s, that is, an insistance on operating these machies as if they were pushrod twins, i.e. at less than 4,000 rpm. That just doesn't work, and everyone back then understood it. And of course folks go down the same "this stuff is junk" path with ignition too. Maintained stock systems are marvels of efficiency.

Finally, the advent of electronic ignition. Your comment here is mostly sound, so I will add only that electronic ignition replaced point ignition for one reason only: the five-year clause in the then-new emissions warranty. And even that wouldn't have done it except the feds went one step further and arbitrarily assembled a parts list on which the points were listed as emissions parts. It was not because of their performance, whether in pre-emissions engines or post-emissions ones. There is no performance advantage in any electronic ignition that is simply a transistor-replaces-the-points type. Both are Kettering, with all the same characteristics, strengths and weaknesses.
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