Coils. 3 ohms?

[Pigford]

Just a general question, coz I wanna know the answer.......
Whats the real gains in running different rated coils. Are higher/lower rated ones better for higher comp motors, or can a lower ohm coil give better spark. Ohhhhh, soooooo many questions
I assume the higher ohm coils need a more powerful ignition.
Whats the rules for changing coil ratings? Can higher replace lower, or other way, and if so/not, WHY
It seems that Turbos run lower ohm coils
Please can someone give us a BRIEF "do's & don't's" guide

[Jeff Saunders]

You need to match the resistance of the coils to the ignition system. You can run higher resistance coils, but not lower.

With points, the factory coils are approx 3.7 - 4.2 ohm on most bikes, you need to run 4 or 5 ohm replacement coils. You can run 3 ohm coils, but the points will pit much quicker.

With electronic ignitions you can kill the ignition if you run a lower resistance coil than the ignition is designed for.

Race bikes tend to run lower resistance coils to get the fattest spark. My old Gerex race ignition on my turbo bike ran 0.8 ohm coils.

Dyna 2000 igntions are designed to run 2.2 ohm coils
The Dyna-S ignition is designed to run 3.0 ohm coils

[Rich]

Lower resistance coils allow the voltage to build up quicker making the spark at high revs better - shorter charge / discharge times. You can fool the ignition into thinking it has a higher resistance coil by putting a ballast resistor in series (as on th Mk2) and this will give a better spark at high revs. As Jeff says you can put a higher resistance coil on although you may get a slightly weaker spark at higher revs but if you put a lower resistance coil on than the ignitor transistors are designed to run at you will probably burn them out.

[Jeff Saunders]

The other part of this is temperature and power consumption.

The lower the resistance coil, the hotter the coil will run and the more power it consumes. I don't understand the electrical theory on this, so someone jump in with more details.

I know with certain motorcycles - one being the early H**** Fours, Dynatek strongly suggests running 5 ohm coils with the Dyna-S due to the weak charging systems on those bikes.

[Pigford]

Rich you said:

Lower resistance coils allow the voltage to build up quicker making the spark at high revs better - shorter charge / discharge times. You can fool the ignition into thinking it has a higher resistance coil by putting a ballast resistor in series (as on th Mk2) and this will give a better spark at high revs.

Thats contradictory First sentence low ohms = good hi rev spark.
Second says Hi ohms = good hi rev spark Is it me just being thick.

Thanks ( & Jeff) for responding as this is probably interesting for a lot of members

[Rich]

"You can fool the ignition into thinking it has a higher resistance coil by putting a ballast resistor in series (as on th Mk2) and this will give a better spark at high revs."

Due to the fact that a ballast resistor alters resistance with the heat generated, the more pulses you put through it the less resistance it has and the greater voltage it passes through. Therefor if you have a 1.5 ohm coil and a 2 ohm ballast resistor at low revs the resistor will have a higher resistance and the ignition will think it has a 3.5 ohm coil and therefor not generate as much heat in the transistor junction as the voltage going through is reduced. As you increase revs the pulses through the resistor increase and heat is generated this reduces the resistance in the resistor and a greater voltage is allowed to pass to the ignition coil as the resistance in this part of the circuit has reduced to probably 0.5 ohms (ballast resistor) plus the coil resistance of 1.5 making 2ohms in all.

The vital bit is the ballast resistor if you just put a normal resistor in there it would act like a higher ohm coil and have a weaker spark at high revs.
If you removed the ballast resistor altogether and just ran the coil at low revs there would be more than the design limit voltage going through the transistor junction and it would probably go POP!

[FER]

See this is why folk at Dyna spend time making lovely ignitions for our bikes . Fit and forget . I'm in love with Dyna 2000 .




fer

[Rich]

2000 - Ah tacho out - adjustable curves it's probably the best value for money going at the moment.

[Pigford]

Rich, thanx mate, just about got that, gonna read it a few times now

[uk kev]

So does anybody know if the Newtronic system will handle 3.0-ohm coils?

[Rich]

So does anybody know if the Newtronic system will handle 3.0-ohm coils?

Mine (when it was called Pirahna) burn't out one of the power transistors (2055) when I ran Dynas on it then I threw it in the bin. Not very helpful I know but :

"The ignition system is designed to use the original coils for your vehicle, this significantly reduces the cost of converting to electronic ignition. Replacement coils should be not less than 3 Ohm primary resistance."

That's pulled directly from their website
http://www.motorcycle-ignition.com/igni ... on_reviews

[Big John]

My Z900 is running a Newtronics system with Dyna coils not sure what resistance they are but will check tomorrow. Already fitted when I got the bike and all seems to be ok. Think I may fit a Dyna 2000 in the future.

[Steve Cooke]

Now I know why I turned to Carpentry

[Pigford]

Steve, maybe it just woodent go

[Steve Cooke]

Pigford your right it just wood knot sink in.