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Its an old story. A 98 ZR 600 EFI stator burns the ignition coils. So what!!! Well I decided that I was not going to be content with just getting my stator rewound just like the one that burned up. Obviously there is a problem with these stators because of the number of posts that we all see about them being burned up. Kev and Blaine have begun rewinding them for people with better quality materials but the same gauge wire and that seems to be working for most.
The problem is heat and what Kev and Blaine are doing is using materials with better heat resistance. But where does the heat come from? Obviously the heat comes from a number of sources. The engine gives off heat and also the coils themselves create their own heat because the current they are making has to pass through the coil wires. Not much can be done about the engine's heat other than to do things that others have done like shimming the recoil or drilling holes in the stator housing. these are good things to help, but as I see it the biggest problem is the heat generated by the coil itself.
So how do you reduce the heat from the coil itself? Just like any other current carrying wire, increasing the size of the wire in the coils will increase the amount of current that can be carried, or it will reduce how hot the wire gets if the current doesn't change.
We don't want to change the amount of current that the coils produce so increasing the wire size will reduce the amount of heat produced by the coil. How do we insure that thee same current is produced? Well, the flywheel magnets aren't being changed and the engine rpm range isn't being changed, so from Faraday's law nothing will change if we keep the number of turns of wire the same as the original.
The original high and low speed coils were wound with 36 and 32 gauge wire respectively. The next larger gauge wires would be 34 and 30 gauge respectively. How do you know how much wire was on the original coils. Well we have specs that say the resistance of the original coils is 450 ohms and 45 ohms respectively and the resistance of those gauge wires is 414.8 and 162 ohms per foot respectively. That means there is 1085 and 278 feet of wire on each of the respective coils. Now the larger wire resistance per foot is 261.3 and 103.7 ohms per foot. From that I calculated that the same lengths of the larger wire would have 283 and 28.8 ohms of resistance. Those are the numbers I used ffor my coil rewinds using the larger gauge wire.
The question is whether you can get enough of the larger wire on the spools. Well I wound them tonight and as expected it was no problem to get enough wire on the high speed coil with about 278 feet of wire. The low speed coil with the 1085 feet of wire was the real question. Well I got it wound and it is very close but I made it. Below are some pictures of the wound coils. You can see that the high speed coil wasn't a problem, but the low speed is FAT.
The next step is to install them into the stator and give it a try. I am confident that it will work. In another thread there was some concern that changing the wire gauge would change the impedance of the coil. The impedance will change, but IMO the change due to the resistance of the wire will be small when compared to the impedance from the magnetic inductance of the coil. The later is much more dominant especially in the light of the fact that there are 6 magnets in the flywheel. This means that the frequency of the magnetic flux change will be large and the inductance from magnetic reactance is dependent on this frequency. To shorten this lengthy dissertation, I have considered this and don't feel it is a big concern.
As I said, below are some pictures of the wound coils as well as winding setup I used. Enjoy.
The problem is heat and what Kev and Blaine are doing is using materials with better heat resistance. But where does the heat come from? Obviously the heat comes from a number of sources. The engine gives off heat and also the coils themselves create their own heat because the current they are making has to pass through the coil wires. Not much can be done about the engine's heat other than to do things that others have done like shimming the recoil or drilling holes in the stator housing. these are good things to help, but as I see it the biggest problem is the heat generated by the coil itself.
So how do you reduce the heat from the coil itself? Just like any other current carrying wire, increasing the size of the wire in the coils will increase the amount of current that can be carried, or it will reduce how hot the wire gets if the current doesn't change.
We don't want to change the amount of current that the coils produce so increasing the wire size will reduce the amount of heat produced by the coil. How do we insure that thee same current is produced? Well, the flywheel magnets aren't being changed and the engine rpm range isn't being changed, so from Faraday's law nothing will change if we keep the number of turns of wire the same as the original.
The original high and low speed coils were wound with 36 and 32 gauge wire respectively. The next larger gauge wires would be 34 and 30 gauge respectively. How do you know how much wire was on the original coils. Well we have specs that say the resistance of the original coils is 450 ohms and 45 ohms respectively and the resistance of those gauge wires is 414.8 and 162 ohms per foot respectively. That means there is 1085 and 278 feet of wire on each of the respective coils. Now the larger wire resistance per foot is 261.3 and 103.7 ohms per foot. From that I calculated that the same lengths of the larger wire would have 283 and 28.8 ohms of resistance. Those are the numbers I used ffor my coil rewinds using the larger gauge wire.
The question is whether you can get enough of the larger wire on the spools. Well I wound them tonight and as expected it was no problem to get enough wire on the high speed coil with about 278 feet of wire. The low speed coil with the 1085 feet of wire was the real question. Well I got it wound and it is very close but I made it. Below are some pictures of the wound coils. You can see that the high speed coil wasn't a problem, but the low speed is FAT.
The next step is to install them into the stator and give it a try. I am confident that it will work. In another thread there was some concern that changing the wire gauge would change the impedance of the coil. The impedance will change, but IMO the change due to the resistance of the wire will be small when compared to the impedance from the magnetic inductance of the coil. The later is much more dominant especially in the light of the fact that there are 6 magnets in the flywheel. This means that the frequency of the magnetic flux change will be large and the inductance from magnetic reactance is dependent on this frequency. To shorten this lengthy dissertation, I have considered this and don't feel it is a big concern.
As I said, below are some pictures of the wound coils as well as winding setup I used. Enjoy.
