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I have a '96 RC EFI that i just installed Screamin eagle plug wires on and noticed that the resistance was around 40K for the shorter wire and 65K for the longer one. The manual says they should be around 4K and 8K which is what the stock wires were. I only changed the wires because i liked the looks of the yellow wires better. I would have upgraded the coil except Harley and a few aftermarket products don't list one for a EFI bike. My bike is mostly stock except for exhaust, intake and a EFO. My question is are these wires with the much higher resistance going cause problems with the stock coil and or performance problems. My second thought is maybe with the increased voltage output of a high performance coil the higher resistance wire would be less of a issue. ???

thanks
 

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WOW - I can't be the first to add SE plug wires with the stock coil!

no has an opion about the resistance difference?
 

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ohm meter setting

-2$en#e- Are you sure your ohm meter is on the correct setting? I am checking my stock wires just as a basis of comparison. In the past I have had the same situation with automobile wires.
 

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my meter has auto-range. Also I had my old set and new set setting side by side on the bench as i was measuring them. Also from my electronics memory I think same voltage out - more resistance = less current = less spark. Am i right or wrong?
 

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If my memory serves me correctly resistence is just that resistence to flow and conductivity is the measure of flow. That being said if two points are connected in a circuit by a wire and have no resistence there will be no flow. So if I am correct with what I remember, the higher the resistence the more flow.Interesting ,I am going to have to check that out as its been a few since I have had to use that part of my mind.
BC:hmmm:
 

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E=IxR with E=Voltage, I=Current, R=Resistance
If you increase the resistance and the current remains the same you will have a higher voltage. Better spark?
 

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bcnasty said:
If my memory serves me correctly resistence is just that resistence to flow and conductivity is the measure of flow. That being said if two points are connected in a circuit by a wire and have no resistence there will be no flow. So if I am correct with what I remember, the higher the resistence the more flow.Interesting ,I am going to have to check that out as its been a few since I have had to use that part of my mind.
BC:hmmm:

Hey BC, you've got it mixed up a bit - Yes, resistance is resistance to flow, but Current or amperage is the measure of flow. As resistance increases, current or amperage decreases. If you connect a wire with no resistance across a battery, you will have maximum available currrent from that battery. As resistance increases, current decreases, so laying a poor conductor across a battery will not cause much current to flow (or any current if it's an insulator).

I used to know more about this stuff but my memory doesn't seem to hold this stuff as long as I would like!!! Luckily I still use ohms law once in a while.
 

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The typical ignition system with a coil is designed to deliver approximately 55,000 volts (V) and 1 Amp (I) to the spark plug.

Let assume the resistance 4,500 ohms (R) of your original wires...

The formula of V=IxR in this case is measuring voltage drop.

V=4,500 x 1 equals 4,500 volts lost against the resistance of the wire.

4,500 ohms is typical for OEM plug wires. High performance wires SHOULD have resistance values lower than OEM. Something is not right with the values you have on the Screaming Eagle wires.

Less resistance means more energy is delivered to the plugs which helps burn the fuel mixture more complete and complete combustion means more power.
 

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Discussion Starter #11
well you seem to agree with what i'm thinking. The only reason i can think of for the higher resistance wire is there made to go to with a high out coil hence higher votage coil + higher resistance wires = aprox. stock current to plugs.

right???

why doesn't anybody make a high out coil for EFI bikes???
 

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Heck, this is got me even more confused. If wire length is directly proportionate to resistance and doubling the length will increse the resistance by two, yet double the width decreases the resistance by half does that mean the conducter in s.e. wires are half the size of stock ?
I went to www.nightrider.com and there is an interesting read on spark plug wires. Now you got my attention and I am on a mission as this is kicking me arse. :wacko:
BC
 

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Discussion Starter #13
I just ran across this post in the Electrical forum,

Harleys plug wire resistance spec is 250~582 ohms per inch-in the past their ignition modules were prone to damage from any plug wires not meeting this spec

it doesn't get anymore specfic - if this applies to all models carbed or EFI ? This range of resistence per inch is very close to the tolorences that the Harley service manual spec out for the stock wires.
 

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I'll Bite

On the last cup of joe (out of this pot) and enjoying a nice warm breezy morning out on the patio. Browsing the forum. Ol's out, & I got the place to myself.

I do believe that increased resistance will decrease amps if voltage remains constant.

Point to ponder... As long as the spark ignites the mixture at the correct time, does is really matter how many watts were delivered?

Suck Push Bang Blow



.
 

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scg said:
I have a '96 RC EFI that i just installed Screamin eagle plug wires on and noticed that the resistance was around 40K for the shorter wire and 65K for the longer one. The manual says they should be around 4K and 8K which is what the stock wires were. I only changed the wires because i liked the looks of the yellow wires better. I would have upgraded the coil except Harley and a few aftermarket products don't list one for a EFI bike. My bike is mostly stock except for exhaust, intake and a EFO. My question is are these wires with the much higher resistance going cause problems with the stock coil and or performance problems. My second thought is maybe with the increased voltage output of a high performance coil the higher resistance wire would be less of a issue. ???

thanks
You ought to check out magnacor.com they're high quality plug wires. I just bought a pair, and they're quaranteed for life.
 

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To throw in another twist to this, what effect does changing plug wires to ones with different resistance, have on the ion sensing for the spark retard system in the later EFI's?
The later (and maybe the earlier ones too, I don't know) EFI models sense detonation through the wires. Does changing them affect how well this system works?
 

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DesertRat said:
E=IxR with E=Voltage, I=Current, R=Resistance
If you increase the resistance and the current remains the same you will have a higher voltage. Better spark?
You formula is correct, but the predicted outcome is not. If you have a higher resistance wire, the E dropped across it will be higher, thus attenuating the voltage at the plug to jump the gap, thus a weaker spark.

The reason for a resistance in the wire is to reduce radio interference.

More than you probably want to know on the subject here.
 

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The only thing I can figure as a benefit to s.e. wires is the type of material used inside to deliver the voltage. from the article I mentioned reading on www.nightrider.com, the factory wires are prone to break down with heat where the type of wire the s.e.are do not. So maybe cold readings show the stock to be better but hot readings are different. Don't shoot, I am not saying this is fact , just what I read. I have to remember to check the wires resistence when I get home because this entire thing makes absolutely no sense.
BC:hmmm:
 

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It's all about the current (I)

if (V) voltage = (I) current x (R) resistance then:

(I) = (V) ÷ (R)

as resistance goes up current goes down

less current = less spark
 
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