Birdoprey
Well-Known Member
Oops! Ya beat me to it Danny!
Birdoprey's COP (Coils Over Plugs) Mod
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Fargo, did you remove the front coils? I told Birdoprey I left them in cause I figured a little extra front end weight would be a good thing with all that increased acceleration! :biglaugh: :biglaugh: :biglaugh: Yeah, right!!
Not surprised about the mpg improvement- it just had to be!! Thanks for letting us know.
It keeps drizzling here and the roads are salty so I can't check mine, but will ASAP!
Done a lot of reading on this tonight (it's not like I'm working at work, please). Sounds like a fantastic mod for the money, and once it's done if you have a coil fail you don't need to rip the whole bike apart, just toss in a new stick.
Got a couple sets on the way already. Since the one thing I'm good at is electrical tinkering, I'll see if I can come up with a bulletproof install for these and post it. Thanks for all the info folks.
Got a couple sets on the way already. Since the one thing I'm good at is electrical tinkering, I'll see if I can come up with a bulletproof install for these and post it. Thanks for all the info folks.
I found this post on another Vmax list. Thoughts?
Okay... IF you are going to use COP (I was) check the resistace of the coils, most COP has to low resistance and will fry the CDI, TCI or if you have a Dyna 3000. Thas why I don't run with my COP....
I checked BEFORE fitting, and I checked with the technichians at Dyna... the COP must be modified in order to work.... and the COP has limited power on waste spark engine. But they would have saved some space.
- Johan
Okay... IF you are going to use COP (I was) check the resistace of the coils, most COP has to low resistance and will fry the CDI, TCI or if you have a Dyna 3000. Thas why I don't run with my COP....
I checked BEFORE fitting, and I checked with the technichians at Dyna... the COP must be modified in order to work.... and the COP has limited power on waste spark engine. But they would have saved some space.
- Johan
naughtyG
Well-Known Member
Well I guess the first thing to do is to compare the resistance of a set of COPs to the resistance of a set of OEM coils with hot wire and boot attached.
If there's a major discrepancy, then we might be slightly worried, but only time will tell.
It's kinda weird that the COPs seem to work so much better than the OEMs if they are so wrong, but electrically it would make sense to get a better spark from the same input if there's less resistance. It would also mean a higher current and so more load on the CDI - all this can be calculated accurately once we have the resistance values.
I still wonder how it would 'fry' the CDI, though.. :ummm: I mean, we've seen quite a few maxes with dodgy cracked coils running like shite for quite a while, but no dead CDIs yet, right?
naughtyG
Well-Known Member
Ok so today I measured the resistance of the rear OEM coils on the input connectors, with the hot wire and boot connected (but not attached to spark plug). Result = 3.1 ohm.
Also today, I received my first set of COPs - these are from an '01 Honda CBR 929 RR.
I measured all four of these using the same multimeter. Result = 1.4 to 1.6 ohm.
So it looks like the COPs have about half the resistance of the OEM coils. This would explain the stronger spark, meaning easier start and better performance. (a bit like the claims of those multi-electrode semi-precious metal spark plugs)
It would also sustain the claim made by that Johan character Mark mentioned that the COPs could fry the CDI.
OTOH, this guy also said that the COPs must be modified. While this isn't strictly true, there is a very easy way around this: all that needs to be done is to mount a 1.5 ohm resistor in series with the COP. This would add to the COP's 1.5ish ohm resistance, and bring it up to the same 3.1 ohm resistance of the OEM items. Dead easy to do - just cut the hot wire going to the COP and solder the resistor there. Remember the resistor will heat up a little under load and mount it accordingly.
It is possible that this will negate the bonuses of the COPs over the original coils in terms of easier starting, better grunt, better MPG etc, but if it means full reliability on the CDI side then it's a must. Also, we will still benefit from the weight loss and the space created by removing the old coils, as well as the ease of coils replacement, especially considering how prone to cracking and failure the OEM items are. The COPS are also WAY cheaper than the OEMs.
Finally, with a little tweaking and some experimentation, we might find that a happy medium can be reached by reducing the resistor's value to anything between 0 and 1.5 ohm, giving back the COPs full advantages but not frying the CDI. Right now, all we can do is wait to see if a CDI does actually get fried (Birdoprey, u gonna risk it?) or start adding the resistors to be on the safe side.:confused2:
I'm also expecting a set of COPs form an '05 GSXR 600 - I will measure those as soon as they turn up and report. Birdoprey, can you measure all the ones you have to see if they change from brand to brand or model?
Also today, I received my first set of COPs - these are from an '01 Honda CBR 929 RR.
I measured all four of these using the same multimeter. Result = 1.4 to 1.6 ohm.
So it looks like the COPs have about half the resistance of the OEM coils. This would explain the stronger spark, meaning easier start and better performance. (a bit like the claims of those multi-electrode semi-precious metal spark plugs)
It would also sustain the claim made by that Johan character Mark mentioned that the COPs could fry the CDI.
OTOH, this guy also said that the COPs must be modified. While this isn't strictly true, there is a very easy way around this: all that needs to be done is to mount a 1.5 ohm resistor in series with the COP. This would add to the COP's 1.5ish ohm resistance, and bring it up to the same 3.1 ohm resistance of the OEM items. Dead easy to do - just cut the hot wire going to the COP and solder the resistor there. Remember the resistor will heat up a little under load and mount it accordingly.
It is possible that this will negate the bonuses of the COPs over the original coils in terms of easier starting, better grunt, better MPG etc, but if it means full reliability on the CDI side then it's a must. Also, we will still benefit from the weight loss and the space created by removing the old coils, as well as the ease of coils replacement, especially considering how prone to cracking and failure the OEM items are. The COPS are also WAY cheaper than the OEMs.
Finally, with a little tweaking and some experimentation, we might find that a happy medium can be reached by reducing the resistor's value to anything between 0 and 1.5 ohm, giving back the COPs full advantages but not frying the CDI. Right now, all we can do is wait to see if a CDI does actually get fried (Birdoprey, u gonna risk it?) or start adding the resistors to be on the safe side.:confused2:
I'm also expecting a set of COPs form an '05 GSXR 600 - I will measure those as soon as they turn up and report. Birdoprey, can you measure all the ones you have to see if they change from brand to brand or model?
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Birdoprey
Well-Known Member
NG, I figured the exact same thing, just was unable to hit autoparts store to pickup the resistors like i planned yesterday. Got lots going on right now, so my testing is gonna have to wait a bit. My thought was to get to 2.5 Ohms total or so. According to a Hayabusa service manual i have, the COP's resistance range is .8-1.2 Ohms. I would think the stk coils would have a simmilar range. This tells me that the TCU can handle a certain range w/o problems. Your not gonna find ALL coils with the exact same resistance. What that range is, i dunno. I've put about 175mi on the COP setup, but they were in 30-40mi stints. Seen no issues, but that does'nt mean there is'nt one. Hard to tell with the TCU.
All the Denso COP units i've checked were 1.0-1.4Ohm.
All the Denso COP units i've checked were 1.0-1.4Ohm.
Thevmaxrider
Well-Known Member
Stock coils are 2.7 ohms +/- 10% at 68F. You will want to get as close to that range as possible I would think. Also, we need to figure out the wattage of resistor necessary, otherwise they will burn out and strand someone alongside the road.
Vinmax
Well-Known Member
Hey Guys,
Here's the problem with just adding a resistor in series with the coil pack,,,,, In Ohm's Law, in a series circuit, the total voltage will be 'dropped' amongst the various resistances of the circuit. The total current will be cut down and can be calculated by adding up the various resistances of the circuit.
In other words, if the current is too high with the lower resistance of the COP, then adding a resistor in series WILL cut the total current flowing in the circuit. BUT, it will also cause a 'voltage drop' across that resistor and another voltage drop across the other resistor,,,,,, namely the COP.
So if you have a COP with 1.5 ohms and use a resistor in series that is also rated at 1.5 ohms, then the total current of the circuit will be cut in half, but each component (one COP and one resistor) will only see half the voltage each. So in effect, you'll be running your COP on 6 volts, and you'll be running that resistor you put in on 6 volts.
That's why we always try to keep connectors clean on our bikes, because the increased resistance, and with it the various voltage drops, leads to NOT getting the full 12 volts to where ever the current is headed. Like a headlight NOT getting the full 12 volts or the charging system NOT getting the full charging voltage to the battery due to dirty connections.
Vinnie
Here's the problem with just adding a resistor in series with the coil pack,,,,, In Ohm's Law, in a series circuit, the total voltage will be 'dropped' amongst the various resistances of the circuit. The total current will be cut down and can be calculated by adding up the various resistances of the circuit.
In other words, if the current is too high with the lower resistance of the COP, then adding a resistor in series WILL cut the total current flowing in the circuit. BUT, it will also cause a 'voltage drop' across that resistor and another voltage drop across the other resistor,,,,,, namely the COP.
So if you have a COP with 1.5 ohms and use a resistor in series that is also rated at 1.5 ohms, then the total current of the circuit will be cut in half, but each component (one COP and one resistor) will only see half the voltage each. So in effect, you'll be running your COP on 6 volts, and you'll be running that resistor you put in on 6 volts.
That's why we always try to keep connectors clean on our bikes, because the increased resistance, and with it the various voltage drops, leads to NOT getting the full 12 volts to where ever the current is headed. Like a headlight NOT getting the full 12 volts or the charging system NOT getting the full charging voltage to the battery due to dirty connections.
Vinnie
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Birdoprey
Well-Known Member
Now i don't pretend to competely understand resisters/capaciters etc, etc. I ran across this:
http://www.hot-spark.com/HS13BR.htm
This is a 1.3Ohm ballast resister, and it mentions only less than a 2v drop(at 4000rpm) and .5watt. Also, do the stk coils have just 12v or does it go up when the bike is running due to the charging system?
http://www.hot-spark.com/HS13BR.htm
This is a 1.3Ohm ballast resister, and it mentions only less than a 2v drop(at 4000rpm) and .5watt. Also, do the stk coils have just 12v or does it go up when the bike is running due to the charging system?
naughtyG
Well-Known Member
That thing looks cool to me. And it's made exactly for what we need!
I would have thought there was only exactly 12V at the coils' input as that is the job of the R/R.
I'm still researching my old electrical lessons (20+ years ago lol) to remind myself of all the formulas to calculate exactly what the deal is with volts, amps, wattage and coil circuit resistance. Till then..
I would have thought there was only exactly 12V at the coils' input as that is the job of the R/R.
I'm still researching my old electrical lessons (20+ years ago lol) to remind myself of all the formulas to calculate exactly what the deal is with volts, amps, wattage and coil circuit resistance. Till then..
There should be 12 volts input to primary coil windings.
Vinmax
Well-Known Member
In electronics, Ohm's Law states that E=I x R. That means Voltage is equal to Current (measured in amps) multiplied by Resistance (measured in ohms). So, if you have an exact 12 volts going to the circuit, and you want the total resistance to equal the original 3 ohms, then what you wind up with is a total current of 4amps. You get that from 12v divided by 3ohms, and that gives you 4 amps of current.
Now, you take the 4amps current and figure what it would take to have the COP drop 10 volts and the unknown resistor drop 2 volts. That gives you 10 volts divided by the 4 amps current, which equals 2.5 ohms needed for the COP (but we can't do that because the resistance is already designed into it and can't be changed correctly by adding a resistor outside it) and .5 ohms needed by the other resistor to drop the remaining 2 volts.
With the ballast resistors sold by that website mentioned above, it just doesn't figure out in our application. You would still have a voltage drop of about 6 volts for the COP and 6 volts for the ballast resistor.
The reason being is, that website is saying that the voltage will drop from 14 volts to 12 because the automotive coil will have a resistance of 7.79ohms.
I got that from taking a 14 volt circuit, then dividing the 2 volt drop for the ballast by it's 1.3 ohms resistance. That gives 1.54 amps that must be traveling in that circuit. Now you take the 12 volt remaining in that circuit and then divide it by the 1.54 amps that we already figured out in that circuit. That figures out to 7.79ohms for the automobile's coil.
The thing is, the COP we're using has a set resistance of 1.5ohms. If we want to keep the total resistance of the circuit at 3ohms, then we wind up with a 4 amp circuit. To add enough resistance to the circuit to retain the 3ohms total resistance and the 4 amp total current, then the coil is going to be running on a very low voltage, namely 6 volts if we're feeding it exactly 12 volts from the TCI.
Vinnie
Now, you take the 4amps current and figure what it would take to have the COP drop 10 volts and the unknown resistor drop 2 volts. That gives you 10 volts divided by the 4 amps current, which equals 2.5 ohms needed for the COP (but we can't do that because the resistance is already designed into it and can't be changed correctly by adding a resistor outside it) and .5 ohms needed by the other resistor to drop the remaining 2 volts.
With the ballast resistors sold by that website mentioned above, it just doesn't figure out in our application. You would still have a voltage drop of about 6 volts for the COP and 6 volts for the ballast resistor.
The reason being is, that website is saying that the voltage will drop from 14 volts to 12 because the automotive coil will have a resistance of 7.79ohms.
I got that from taking a 14 volt circuit, then dividing the 2 volt drop for the ballast by it's 1.3 ohms resistance. That gives 1.54 amps that must be traveling in that circuit. Now you take the 12 volt remaining in that circuit and then divide it by the 1.54 amps that we already figured out in that circuit. That figures out to 7.79ohms for the automobile's coil.
The thing is, the COP we're using has a set resistance of 1.5ohms. If we want to keep the total resistance of the circuit at 3ohms, then we wind up with a 4 amp circuit. To add enough resistance to the circuit to retain the 3ohms total resistance and the 4 amp total current, then the coil is going to be running on a very low voltage, namely 6 volts if we're feeding it exactly 12 volts from the TCI.
Vinnie
I don't have a diagram of the ignition circuit so I'll stick to a couple of general statements.
Vin is correct in that adding another resistor is not the way to go here. The voltage drop caused before the COP in the circuit will diminish output on both the COP, and subsequently the plug secondary V provided for the spark will be lower, causing a weak spark.
Without knowing the specs on the stock CDI unit, I'm unable to say whether or not the COP mod will kill it off the top of my head. We can say that the mod should provide a longer spark (you guys running this can probably gap up a little)
I'm going to go snoop around the internet for some specs / schems and figure it out, then it's sunday night with the inlaws (yay?) Will get back with ya tomorrow.
EDI: heh, apparently Vinnie and I were typing at the same time there, but yeah, extra resistor = bad.
Vin is correct in that adding another resistor is not the way to go here. The voltage drop caused before the COP in the circuit will diminish output on both the COP, and subsequently the plug secondary V provided for the spark will be lower, causing a weak spark.
Without knowing the specs on the stock CDI unit, I'm unable to say whether or not the COP mod will kill it off the top of my head. We can say that the mod should provide a longer spark (you guys running this can probably gap up a little)
I'm going to go snoop around the internet for some specs / schems and figure it out, then it's sunday night with the inlaws (yay?) Will get back with ya tomorrow.
EDI: heh, apparently Vinnie and I were typing at the same time there, but yeah, extra resistor = bad.
Birdoprey
Well-Known Member
I wonder how hard it would be to add heat sinks to the stk TCU? Would'nt that do it? May be too much trouble or cost. Dunno.
Dunno how to find out what the stk TCU can handle. Guess i could just see how long it lasts...might not be fun being stranded in the middle of West Texas though! Working on a sinus infection this weekend, can't think clearly...!
Dunno how to find out what the stk TCU can handle. Guess i could just see how long it lasts...might not be fun being stranded in the middle of West Texas though! Working on a sinus infection this weekend, can't think clearly...!
blvdblaster1200
Well-Known Member
this is why i asked for the resistance specs before .the busa cop's were very close to the stock max coils i believe you stated?and 1 question,is this resistance spec you guys are chasing primary or secondary resistance?if its secondary it can be fixed by adding a resistor in the plug boot assuming this model comes off-most car cop's do but i dont have one of these in my hand.im guessing its in the primary though.
RagingMain
Well-Known Member
I used the R1 COP and harness.
RagingMain
Well-Known Member
Danny,
Nope didnt remove the front coils. Didnt feel like going into it, I was lazy. The wiring harness is so easy to get to. Plus from reading the rest of the post I might be going back to my original set up when I fry my TCI from running my COPS.
So far I have put on over 300 miles on COPs with one trip being close to 100 miles and no problems. Keep your fingers crossed for me.
So basically what all you electrical inganers are saying is we need a way to keep keep the amperage the same on the TCI??? So how do we do that???? Could we do anything with a parallel circuit??? Just wondering. Definately need to keep the voltage at the primary coil 12 volts.
Cheers
Thevmaxrider
Well-Known Member
You are correct it is the primary that we are discussing. Understanding that if I lower the resistance the current flow will increase, but in a 12V system and a 1 ohm difference we are not talking a lot of current here. I am wondering if this is assumption on someones part or did anyone out there have a CDI box burn up on them from running COPs?
naughtyG
Well-Known Member
What we found so far is that the OEM coil's primary circuit has a resistance of 3.1 ohms. (mine anyway - 1986 Vmax)
The COPs I tested ('01 CBR929RR) were 1.4 (3 of them) and 1.6 (one of them).
This means they are about half the resistance. Taking the formula I=V/R, where I is the intensity (in amps), V = 12 volts and R being the resistance, we get this:
OEM
12/3.1 = 3.87 amps
COP
12/1.4 = 8.57 amps
So in theory, the COPs are drawing about twice as much current from the circuitry. However, due to the very ephemeral nature of an ignition circuit, I'm still not quite sure how much it matters. I also wonder if it would affect earlier ignitions (like mine) differently than later ones. (Yamaha changed them in the 90's, right?)
I'm also not really clear on how much a small voltage drop would affect the coil's performance, but assuming that an automotive coil has a winding of about 1/100, every volt counts in making a good strong spark.
I guess the next best thing for those running COPs (and I am still considering it too) would be to get a spare CDI just in case, and really only time will tell if there is indeed a problem, or not. :ummm:
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