Pinned Coil On Plug conversions - COP

I figure there is enough interest on this topic to have a dedicated thread for it.

Some good links to read:

http://www.v4spark.com/V4-COP.htm

http://www.sportdevices.com/ignition/ignition.htm

http://www.dtec.net.au/Ignition Coil Dwell Calibration.htm

https://spdispark.com/pages/frequently-asked-questions-dwell.html

http://www.jetav8r.com/Vision/IgnitionFAQ.html

There are a few reasons why you would want to do this mod. You will be replacing your old coils with newer ones (they can and do go faulty, as well as degrade with age). You eliminate the spark plug caps and high tension leads as failure points. If you have a coil on plug unit fail they are easier to replace, as you only need access to the plugs, whereas the old coils are usually bolted to the frame somewhere. Generally the new coils are lighter, so you save a small amount of weight as well.

If you run an aftermarket programmable ignition unit, you open up options for using direct fire instead of wasted spark, as well as programming dwell time and ignition advance.

For the record, our 4cyl 250cc grey import shiteboxes use TCI - Transistorised Coil Ignition and not CDI - Capacitor Discharge Ignition. What's the difference? Look in the links above.

When selecting which coils to use, there are a few things to consider:

Resistance of the standard coils vs. coil on plug units is the main concern. For example on the ZXR250C, one coil (firing two plugs) has a resistance range of 2.3-3.5 ohms on the primary side. Therefore, the primary resistance of the coil on plug unit (firing one plug) must be half of this, so 1.15-1.75 ohms is the range you would need.

If you use coils with too low a resistance, you stand at risk of overheating the bike's standard wiring, damaging the coils, and damaging the TCI unit. You will not gain anything by running low impedance coils.

You also have to consider the physical dimensions of the new coils. They have to be the right height, and the seal up near the connector has to match the diamater of the of the old spark plug cap. On bikes with exposed plugs like the FZR250, you don't have to worry about this.

OK, so you've selected some coils and now you need to wire them up. How do you do that? With a standard TCI unit, it has to be done so to work with wasted spark. @my67xr made a nice picture so I will use it:






The only thing I would change here is leaving some wire untaped from the connectors, so if you go for a dyno run it makes it easier to get the engine RPM signal off the spark lead.

Will get some pictures of my conversion with the ZXR as it takes place in the next few weeks.

 

After playing around with the 12790-4840 coils I found they are twice as long as the need to be.



For a good fit on the ZXR250, the length from the tip of the coil to the first edge of the oil seal needs to be 2 inches. Then the oil/dust seal will work and you won't foul against anything.

 

I don't as of yet, but I will get some pics. I know what length coil I'm chasing now so will do a comparison.

 

Unsure. Just looking at ebay, Denso 129700-4740 should be a perfect fit.

 

Scratch those off the list then.

Just checked the service manual for the Ninja 300 in the resources section, range for the primary winding on the coils is 1.1-1.5 ohms, they should be suitable if the length is OK. And they are cheap.

 

They might fit the bill perfectly. Good find.

 

OK after firing off a message to an ebay seller with Ninja 300 coils, I got the measurement I've been chasing - the length from the tip of the coil (with the rubber end removed. The reason for this is because the rubber tip extends further down. The plastic end underneath stops on the flat edge of the metal tip of the spark plug) to the beginning of the seal near the connector. On the CBR1000RR coils, it is 3.4" but with the Ninja 300 coils it is 2.6" - so they are nearly a whole inch shorter.

I'm hoping that the Ninja 300 coils will fit and clear the radiator shroud/fan without having to make modifications, and be less likely to vibrate loose.

 

Thanks kiffsta, the seller on ebay offered me a set of 4 for $70 posterd so I took them up on it. Next time

 

Only 1 set for a ZXR