Dave wrote on Yesterday at 14:07:17:An electric cooling fan will likely not be of much benefit, as you would need quite a bit of air flow to make much of a difference. The Savage charging system is only 100 watt, and that has to power all the lights, the ignition and keep the battery charged.....there is not a lot of electric power left over for running other stuff. (My water cooled bikes do have pretty significant cooling fans in the radiator that comes on when the temperature spikes - the charging system is built to handle that electric load).
Have you collected any data from your head temperature thermocouple, that you could share, to give us some idea of how your machine's head temperature varies with load, vehicle speed, and ambient temperature? Is gage temperature highly variable, or relatively constant? What gage and thermocouple did you install?
I wouldn't think one would need to rate an aux. cooling fan for anything like continuous duty when budgeting power from the charging system. It's only used when one is stuck at a light, or otherwise stationary. I'd look at it the same as the starter motor load, namely extremely intermittent.
The fan motor on my liquid cooled Shadow 1100 draws about 5 amps, but it only comes on for a few, very short intervals during a typical ride. I'd estimate something like 1 minute of fan cooling for 25 minutes of cross town urban riding, and much less operation if I'm riding continuously on the highway or a country road. That's equivalent to a continuous load of 200 mA, which is 2.8 watts at 14V. One could certainly make room for that much additional power consumption by switching one light bulb on the bike to an LED.
This amount of power consumed results in enough air movement to disperse the heat from the 1083cc. I would think it should be adequate to cool the 652, even allowing for the inefficiency of not ducting the air flow. It doesn't take much air flow to break stratification and start transferring heat.
One can take advantage of the large radiating heat transfer area already built into the engine, rather than trying to duplicate it in a secondary system, that will be more reliant on air flow, because of its much smaller surface area, than the engine itself. After all, the heat first goes into the metal of the engine, then is transfered to the lubricating oil, then to the material of the oil cooler, and only then to the air. Using the engine fins to dissipate the heat, as designed, means two less transfers, none of which are perfectly efficient and all of which have thermal resistance.
Here are some thermal conductivity coefficients:
Aluminum: 237 W/(m·K)
Steel: 45 W/(m·K)
Water: 0.6 W/(m·K)
Oil: 0.14 W/(m·K)
Air: 0.026 W/(m·K)
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