Do I need inline resistors for the short COPs?

[AMechEng]

I bought a set of short COPs off a 05 GSXR 1000. I am ready to wire it up but I am wondering if I need some inline resistors. My bike is an 86.
The COPs are reading 10ohms across the primary connections and 13.5Kohms across the secondary connections.
Thanks!

 

[ninjaneer]

There's a couple school's of thought: 1) nah, 2) yes. lol. but seriously, some of the earlier pioneers don't run with resistors and haven't had an issue. i personally spliced in some. by not putting in resistors, as slim to none as the risk may or not be, the possibility of frying your ignition unit looms. by putting in resistors, even if the risk is slim to none, the risk is absolutely nullified. If you have a dynatech ignition unit, then you absolutely MUST put in some. just a point of context, garret fabs-in the resistors in the plug and play harnesses that he sells. putting them in doesn't hurt anything, you don't lose performance, whether or not you believe your ignition unit is in jeopardy because of the lower load that it sees. if i remember correctly, you basically want a set of resistors that make the ignition unit see a 3 ohm load. putting resistors is pennies to the dollar compared to being down and hunting for a replacement ignition unit. just my two cents. i prefer to err on the safe side.

 

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I'm pretty sure the dyna ignitions AND the 85-89 OEM ignitions had a higher failure rate if not installed with resistors. 90+ oem ignitions seem to work ok without them but it doesn't hurt as Greg says.

 

[wildweasel_pt]

Like Mike said earlier TCIs are known to need resistors and later ones are known to be more current friendly... Those readings on the primary winding are wrong. You should be getting something close to 1-1.5 Ohm or close by.

 

[AMechEng]

Ya I realized they seemed too high and I re-checked with a different multimeter and read different values. I hate when the batteries start to go on a multimeter. The new values are 2 ohms for the COPs and 3.2 for the OEM coils. So I need 1 ohm power resistors in series. I was doing some math trying to figure out what power rating is needed.
12v / 3ohm = 4 A
4A^2 * 1 ohm = 16 watts for the power resistor
4A^2 * 2 ohm = 32 watts for the COPs

BUT

At 10000 RPM (worst case scenario)
10000 RPM * (60 s/m) = 167 RPS
167 RPS * [(2 sparks/cycle) / (4 rotations/cycle)] = 83 sparks per second
83 sparks/sec * .001 second spark duration = .083 or spark 8% of the time
This makes the assumption that spark duration is 1 ms.

So 16 watts * .083 = 1.3 watts of effective power dissipation.

Let me know if I am way off. I am just thinking that about any power resistor with a 1 ohm resistance will work.

 

[ninjaneer]

i'm thinking your off with the power ratings. the pioneers have already figured it out--satariel666 to be exact if memory serves me well. i want to say 10W or 25W, but let me hunt down the thread to know for sure.

 

[ninjaneer]

here's a post where prez summarizes his analysis that he performed 1-2 years earlier: http://www.vmaxforum.net/showpost.php?p=151777&postcount=22. a couple posts later in the thread he states the use of 30W as ultrasafe and some other thread altogether he states 10W is "pushing it". i wish i could find he original analysis. it was quite humorous following him and another member fighting over the proper technique for finding the correct resistance, power rating, resistor technology.

 

[Redbone]

i'm thinking your off with the power ratings. the pioneers have already figured it out--satariel666 to be exact if memory serves me well. i want to say 10W or 25W, but let me hunt down the thread to know for sure.

Yes, it was Prez who was working with Mark's (Birdofprey) original setup. I don't think Mark ever saw the need for the resistors but we should all be thankful to him for bring COP's to our attention. I bought a early set from him and they worked great on my '92 with some '04 R6 COP's I purchased off of Ebay.
Gannon (88vmx12) the maker of our current resistor COP's (w/ input from Prez once again) took the wiring harness to the next level with the proper connectors and addition of the resistors. I bought a set of his harness's in anticipation of running a Dyna 3000 which I will employ on the upgraded 2013 version of Redbone.
Both versions, the original non resistor setup from Mark and Gannon's set w/ resistors have worked flawlessly on Redbone for 4 years. I'm happy with my COP experiences and judging from others responses it a wholly successful mod for the Vmax.

 

[naughtyG]

I ran a set of long COPs with my '86 while in FL and did a few thousand miles without any problems - no resistors.

From memory the ones burning out were the Dyna ignition boxes, Yamaha TCIs seemed ok. There was a difference in current though, as the COPs I used were between 1/2 and 2/3 of the resistance of OEM coils.

 

[88vmx12]

I ran a set of long COPs with my '86 while in FL and did a few thousand miles without any problems - no resistors.

From memory the ones burning out were the Dyna ignition boxes, Yamaha TCIs seemed ok. There was a difference in current though, as the COPs I used were between 1/2 and 2/3 of the resistance of OEM coils.

And early CDI's burn up!:bang head:

G

 

[Bill Seward]

I guess I'm one of the "pioneers" with this whole COPS mod. I made up a set a few years ago - bought all the parts I needed off Ebay, and after a bit of soldering - was in business.

The setup is working fine. Didn't add resistors, because nobody ever thought about adding them at the time I made up my set.

That being said - if I were to do it over again, I'd spend the money and add the resistors.
(even though I don't think they can help fix a problem I never had...)

 

[AMechEng]

I'm guessing that if a CDI is weak having the extra current may help put it over the edge. I'm going to add some one ohm resistors.

 

[wildweasel_pt]

Tell me if you find some small cylindrical ones please... 20w suits me fine. Anything with more power will make them be bigger and bulkier.

 

[fogman62]

would you show an installation diagram on where to put the resistors.,

Thanks,
Gary

 

[wildweasel_pt]

Just put them inline in either wire...

 

[AMechEng]

Ya they go in series. I'm guess that they have to be attached to the frame of something else to sink the heat from them.

 

[ninjaneer]

AMechEng, you are correct if you are using resistor blocks that require bolting into a heat sink in order to achieve the claim dissipation numbers.

 

[wildweasel_pt]

Ya they go in series. I'm guess that they have to be attached to the frame of something else to sink the heat from them.

It depends on which resistor you use. Some of them are rated for being on open air and have ratings for 25?C open air and no heat sink plate.