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4th gen Coil on Plug mod (split thread)


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Youll be sinking alot more current is the problem. Your going from around 3 ohms to less than half of that.

But is it really a problem? And that's just the primary resistance. We don't know what the impedance value is for either of the coils.

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But is it really a problem?

Maybe, maybe not. But as I mentioned before CDI coils have a different step up compared to TCI coils. DCI coils have a lower step up and need a couple hundred volts on the primary coil to get the 30-50kV on the secondary required to get a spark. The primary coil of a TCI coil is charged with regular 13.8V.

I think it is highly unlikely you will get a spark (or one that has enough energy for ignition) out of a CDI coil charged by a TCI box.

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None of the coils being talked about here (as far as i can tell, f4i, 600rr, busa) are cdi. Almost all stick coils are gonna be tci.

Also, for the 3rd gen/4th gen the busa coils might be the way to go, due to them being the shortest. I just ordered some, we'll see if they fit better.

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Well, thats probably cdi. But i know the mentioned ones are tci. From what i read about the aem coils (and they may be different) you can use them as tci OR cdi.

Back to square one then, the RC crowd has already proved this works on their bikes. 1 coil per plug on those bikes, swapped to 1 cop per plug.

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Ok, if someone can tell me how to wire this up in plain english, I'll buy the coils and wiring harness, and be the guinea pig. I just need to know how to make the changes...

I may be able to accommodate... I could take my F4i harness and coils and modify them so that you can plug them in on your bike and test them. If you don't explode and die, and nothing fails on your bike, then you can replace my parts.

Since we're starting with 4 coils and using 4 cops, we could just plug them in directly like the oem stuff. Changing from that is the part of this mod that I don't fully understand and as such am hesitant about.

That's what I was thinking, but I don't know too much about this stuff either to be completely honest. I know the RC-51's are fuel injected, and our 750's are carb'd, but I have no idea on if their ECU is CDI or TCI, I'm not even sure what CDI and TCI mean...There's gotta be a way to make this work, as many people on here have done much more complicated mods!!! Weight savings would be nice, but I just want a less complicated wire harness, and to avoid the issue that popped up on the way to and from Mugello that had to do with a coil that wasn't properly re-installed, was too close to my exahsut, overheated, built up too much resistance, and stopped working, thereby shutting the bike down!!!

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Well, thats probably cdi. But i know the mentioned ones are tci. From what i read about the aem coils (and they may be different) you can use them as tci OR cdi.

Back to square one then, the RC crowd has already proved this works on their bikes. 1 coil per plug on those bikes, swapped to 1 cop per plug.

And they're using the 2 wire cops as well, so there has gotta be some similarities...

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If you look at the superhawk wire harness (which is another bike that people swap straight to cop's) there is a box called a "converter" that actually fires the coils from a module similar in appearance to ours. Perhaps if we had two of those modules to wire into our harnesses they wouldbproperly control the coils without the need for other current limiters. Also fyi, the F4i coils i have measure 1.09 ohms on ourlow resistance ohmmeter here at work. So if the vfr coils measure 3 ohms we could put a 2 ohm 60w resistor inline on a heat sink similar to this one http://parts.digikey.com/1/parts/763471-resistor-2-00-ohm-60w-1-220-mp2060-2-00-1.html we might be ok.

Secondary resistance figures stated here, not primary***

Edited by flyguyeddy
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Likely a low voltage (5V-12V) pulse/signal to a high (200V-400V) voltage pulse.

Isn't that the coil's job? I don't see them passing all that voltage through the tiny 18-20ga wires to the coils? Is it possible that it's a rev limiter?

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No, that is one of the differences between CDI (Capacitive Discharge Ignition) and TCI (Transistorised Coil Ignition). CDI uses a charged capacitor (charged by an inverter) that is being discharged over the primary coil. A 'CDI spark' lasts not as long as a "TCI spark' but is more powerful, and is more suitable for high rpm engines. A TCI coil is charged by charging it with a current. It takes some time to charge the primary coil due to impedance, this is called dwell time. It also takes longer to discharge: the spark lasts longer.

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Those two boxes would be easier to hide than coils and wires. And you get a better spark in return, which is why vtr1000 owners swap to cbr coils in the first place. And yestwo boxes for our needs.

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