coils/ballast

[bikerphil]

I working on a member's 79SF and the bike has Dyna DC4-1 grey 2.2 ohm coils installed on it. Would it be safe to bypass the ballast resistor without frying the TCI, what do you guys think?

[TopCatGr58]

Hey Phil,

Due to the sensitivity of the TCI, I would find a different ballast resistor if possible, one that is closer to 1 ohm vs. the 1.5 ohm level. Bypassing it would allow it to draw too much current thru the output transistors of the TCI due to too little of resistance vs. the required 3 ohm level.

The Dynatek site stated with the 5 ohm coils for the installer to use a 1 or 2 ohm resistor in line if the 3 ohm coils were used vs. their 5 ohm style. And that they were not responsible for possible damage done to an ignition module if the wrong resistance type coil was installed that didn't match the requirements of the ignition unit.

T.C.

[bikerphil]

So the 0.8 ohm resistor should work if I'm thinking correctly, 2.2 + 0.8 = 3

Thanks TC

[TopCatGr58]

Well,

Crazy Steve and 3Phase/Scott haven't posted to correct me, so it looks like I got this magic smoke question right! The TCI wants to see the 3 ohm level of resistance, whether it be with 3 ohm coils, or 1.5 ohm coils and 1.5 ohms B.R., or any other combination as long as it's at least ~3.0 ohms. IF it's a little more...ie. 3.2 or so won't hurt, but when it's too low/little, that's when more current is drawn thru the TCI and that's where the damage occurs. If you can find a 0.8 ohm resistor, cool, if only a 1.0 ohm, that's also OK.

I remember reading on the Dynatek site somewhere that the coils weren't that sensitive to the actual voltage...ie. 12 vs. 10 vs. 6....that they would work with any of them. However, understanding that the higher voltage allows a stronger magnetic field to be generated before it collapses, and that allows a stronger resultant spark when released, so the higher the voltage going into the coil, the better/stronger spark you'll get....but these are also hi output 30Kv coils, and so ....I don't know the MATH, but with ie. 10 volts vs. 12 volts, you might get 25Kv instead of 30Kv output....but that's still 10Kv stronger than OEM's 15Kv.

The higher the B.R. used, the less actual voltage will get thru, so using a 0.8 ohm B.R. would be a little better than a 1.0 ohm, but I wouldn't worry about it if all you can find is a 1.0 ohm unit. The 1.5 ohm OEM B.R. is a bit much and causes an unnecessary/unwanted amount of voltage loss, but won't hurt the TCI.

T.C.

[bikerphil]

Yep TC, they make a 0.8 ohm resistor for automotive applications, I may give that a try. The bike is running fine the way it is now but the plugs are a little sooty.

[crazy steve]

One thing to keep in mind is the resistor's actual resistance can change slightly in use from heat. The OEM resistors I've checked measure out at about 1.1 ohm 'cold', once they heat up they measure at 1.5. You'll probably have the same effect with a lower ohm rating resistance, whether that makes a big difference is hard to say as the 'rating' may be at operating temp. Much the same at a lamp; the typical turn/brake filament measures at about 2.2 ohms 'cold', increases to 6 ohms when fully lit. Just something to think about....

[bikerphil]

Thank you Steve, that is good to know.