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Hello,

I installed the Flamethrower coil and can tell a difference in 20000V versus 40000V. However, it appears that the engine runs about 15 degrees Celcius hotter with the stronger coil. Is this normal?

Thanks!

Marcus

Pure speculation on my part, hotter spark allowing for more complete burn causing the same effect as a lean mixture.

May look at readjusting (richening) the idle mixture and playing with the timing.

Once more this is only a guess; let us know if you discover anything.

Just curious how you determined the temp difference between the stock and flamethrower coils? Is this something guys who have converted should be worried about?


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Better spark = more fuel burned = hotter engine.

It would help to know under what conditions and where you made the temperature measurements.

Useless factoid: it is the gap in the sparkplug the sets the voltage; once the voltage is high enough to jump the plug gap (and rotor gap) then the voltage doesn't go higher (it actually is reduced due to the plasma in the arc) but now the current that the coil can produce will flow. Like in welding, more current means more heat and in a spark plug this means easier/better ignition of the fuel. But a coil that is designed to allow for a higher voltage can jump a larger gap; this means you can gap your plugs larger and take advantage of the extra oomph. As an example, I'm running an old Jacobs CDI system and coil in my otherwise stock 710M and the plugs are set to 0.060 - 0.070" gap! (as recommended by Chris Jacobs himself). Jim L. says he can feel the difference in performance. I KNOW it runs better, stronger, and smoother, expecially in the cold winter months where the stock system made the engine feel "wimpy"; the rich mixture needed for starting in the cold just wouldn't ignite as easily as it does now.

As Jim pointed out, not knowing the temps involved and without reading the spark plugs I probably shouldn’t have assumed a possible lean condition. You may have been running rich and the new coil helped create a condition where it is now in a better state of tune. The increase in temp may simply indicate that the motor is now getting up to a proper temperature.

Its been so long since I even thought about reading spark plugs! What a lost art. But oh, what tales they tell. Thanks for bringing that up!

Thanks guys for all the answers. I suspected that a hotter burn will increase the temp of the engine. Maybe I will keep the coil for winter and reduce the voltage for the summer. Measurement was done by looking at my trusted temp indicator. After I installed the new coil, I was letting off the accelerator at 72 MPH (GPS reading), and warming up to 110 Celcius, not overheating however. I don't believe I am running lean, as I live at 6800 feet of altitude. At a hot summer day, my density altitude goes up to around 8000 feet. I will re install the factory issued coil and look at the temp once more.

Marcus

72 is too fast for a 303. You are red-lining everything at that speed.

If you see this 15 degree temp increase with the new coil, I would suspect that your timing may be off. For example, if the spark was weak, the timing may have been advanced enough to get as much power from the burn as possible. Now that you have good spark the burn is better/faster, but if it is too advanced it goes into making more heat instead of making more power (that is to say, you really have to have your foot into it to make enough power and burning all that gas makes more heat than you had before).

I wouldn't expect better spark, by itself, to change the temp; assuming the engine is in good shape and tuned properly.

Thanks. I will check the timing.
Vince , I let off the accelerator knowing that that speed can't be right for the old boy. He likes to run at 60 long distance.
Marcus