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Discussion Starter #1
They always say that when you gain one thing you lose another or the other way around. If coils that have less ohms charge faster, than why not run 1.5 instead of 3.5? I'm just curious, I have to run a different coil. I found out that the coil I've been running is not the 3.5 that was on the box but 4.8. The reason why I ask is cause I have a 2.8 but don't know a lot about coils to know if that's a good idea or a bad idea.

Aaron
 

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Aaron--you're just trying to find out if jB is alone tonite, right? You know he'll be all over this query. i look forward to it.

I, for one, would be very interested (oops, my technical writing professor said never use that word "very") in the basics of coils &c. and their characteristics and how the guy that invented it figured it out . . . {from a motor cyclsits point of view. I mean when the first combustion engine was made, how did they get spark? I know I know, all I have to do is google it.
s
 

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you want the lowest resistance you can use to accomplish burning the gas for the time period desired. anything more is probably a waste or inefficient. the lower the number, the less resistance so the more draw on the battery. the higher the number, or resistance, the less draw on the battery. that equates to how much (primary/battery??) voltage youre using. lower number, the battery gets used more. there is a formula you could use to calculate, with measurements, exactly what you need im sure. based on rpm, elapsed time, etc... so that way you could get exactly what you need, then leave room for a bit. the other important thing i remember about it is induction ratings. and i remember thats a big part of the eqation. how it all works, i cant exactly remember. im going to see ron today, he'll know exactly what's up with it all. it seems like youd be able to work it all out wiht those basics though. my question is, why not pvl???


jb??


jc
 

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i should also add, that i think you want to use the lowest resistance becasue it provides the best spark.


j
 

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2.8 ohms would be fine unless you are running a four cylinder at 25,000 rpm.

3.5 ohms is fine for our twins.

Lower resistance for the most part only means faster charge time on the coil. Output voltage is not a function of resistance, it's a function of input voltage and the ratio of windings between the primary and secondary windings.

Lower resistance provides quicker charging but it draws the battery down to a lower voltage, the lower voltage to the primary winding causes lower voltage output to the secondary windings.

A 5 ohm coil consumes about 28 watts, a 3.5 ohm about 40 watts. In general I always opt for the highest resistance with that will charge in the appropriate amount of time. Other wise you are just using up more battery power that get's wasted heating up the coils and sending more current to the plugs, which you don't want, you want voltage.

Lower resistance only provides more voltage in a situation where a higher resistance coil doesn't have enough time to fully charge. 2.8 ohm would work, just might use a little more juice. 5 ohm is too high for our twins. 3.5 is just about right, kind like the Three Bears story.
JohnnyB
 

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but thats if the coils are the same. primary resistance and secondary resistance can change too right?? also, things like plug wires and coil induction make a difference no?? i asked, but he was no help. unless he can take everything and set it up and personallt test each piece, he cant tell me anything. lower resistance does mean a higher voltage spark though. but you do sacrifice battery life.


good luck

jc
 

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What lower resistance does is allow the coil to more fully charge than would a higher resistance coil. The net effect CAN be more voltage. But if you took a 5ohm coil and a 3 ohm coil, both with the same winding ratios, and fully charged them the lower resistance coil would send no higher voltage to the plug.
But seeing as very few OEM coils are choosen to be fully charged between each discharge you can cheat by using a lower resistance coil, faster charge time, stronger magnetic field to collapse, more voltage. But there is a limit to that.

Performance coils use a lower resistance to drive a higher winding ratio. To simplify it, if your primary coil has 100 turns and your secondary has 10 turns and you pump 12 volts into the primary you get 120 out of the secondary (or maybe it's the reverse). To boost output voltage you have to increase the number of primary turns, more primary turns takes longer to charge up, so they use a larger wire with less resistance which allows more current to flow into the primary faster.

The higher voltage output of a low resistance coil is not a function of the low resistance, it's a function of the winding ratio. Which REQUIRES a low resistance to provide an adequately low charging time.

However...the reverse is NOT true, a lower resistance coil does not by promise a higher voltage to the plug, unless the coil is designed to produce a higher voltage. That's why coils are usually rated by both primary resistance AND output voltage. You can have a 3 ohm coil that makes 30,000 volts, or a 3 ohm coil that make 50,000 volts. Depends on the winding ratio, wire gauge, core material etc.

But for the most part, you can be pretty sure, like JC suggests, that an aftermarket performance coil with low resistance is going to send more voltage to the plug.

But remember...an OEM coil with no markings that reads low primary resistance has probably just got some shorted windings in it. Which of course show a low resistance but don't do shit for output voltage.

I learned all this by watching Spiderman 2 tonight. It was that good.
JohnnyB
 

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i know that inductance has something to do with it and henrys. i read up on all of this a long long time ago but only remember bits and pieces. depending on how its wound depends on henrys output or something like that. so more important than ohms, is how the coil is wound. and i think thats what ron was getting at. anyway, apparently if you want a better answer, you'll need to provide more specifics. and im agreeing with jb here.

im geeked out for the night


jc
 

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I know impedence always gets me screwed up. I have no idea how it works with electricity.
I do know what when Aaron is in front of me...he's usually impeding my progress, but I'm not sure if it means the same thing.

And yeah, it's way more complicated than ohms and volts, windings do all kinds of strange shit that I don't understand. I don't even think about it, I just go out and buy a freakin coil that's a bright color...almost all the ones that are bright colors work great on racey things.
JohnnyB
 

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eh, even though aaron asks a question and it sets off a 6 page diatribe, i think its still worth while. i dont take anything anyone tells me as gospel. its great to have a few opinions to make your own decision. im sure just saying to buy a yellow or red one made him cringe. probably because he knows thats what id really do. id like to hear what other people think on most of this. i like seeing opposing opinions that are presented in a non confrontational way. i''ll let mark and marcus have the confrontations. and, i'll have a cinnamon scone with that.


jc
 

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I want to have a set of leathers done up just like a Spiderman suit...with matching helmet...whadda ya think of that?

Ohm <<<<--- technical content.

JohnnyB
 

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Discussion Starter #17
I went away this weekend but had a feeling when I got back I'd have to sift through Joes blah, blah, blah to get my answer.

Is anyone one racing Mid-O or Carolina Motorsports Park?

Aaron
 

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we kicked around nelson and decided to save for nhis. id love to do cmp, but i dont think its in the budget for this month. (i hate paying car insurance!) especially the week before nhis. i'll probably do nhis, summit, and vir for the rest of the year. its probably going to kill me as far as points go for not showing at cmp, but i just dont think i can do it. have you ever been there aaron??? i hear it sucks as a drive. typical s.c. highways.


so, buy the yellow one wasnt a good enough answer??? we need more to go on than just the info you gave.


blah blah blah....


that was just for you.

jc
 

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Discussion Starter #19
Actually Joe I gave just right amount of info cause I knew Johnny would cover all the rest of what I was looking for. I know how coils work, I just wanted to know of all the draw backs to low ohms. Also why don't you prduce a none stock motor and race bike that's reliable and then speak of how you do it, you know like from experience.

I've never been to CMP.

Aaron
 
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