Regardless of which fan switch temperature set-point you chose, high or low, the overall capacity of the cooling system doesn't change.
Said another way, if your engine is getting hot enough to blow coolant with the stock higher set-point switch, then using a lower temperature set-point switch will not, in and by itself, keep you from blowing coolant.
A higher pressure radiator cap would raise the temperature at which you start blowing coolant, but radiator surface area and air flow are still the primary determinants of how many BTUs/second can be removed from the motor. Wetting agents might improve heat transfer efficiency to yield a marginal increase in cooling capacity.
Adding a second fan significantly increases air flow at low bike speeds and, therefore, the effective cooling capacity of the system is also significantly increased when the bike is moving slowly, but switching both fans on at a lower temperature does not increase the maximum rate at which BTUs can be extracted from the engine. Similarly, using a lower temperature thermostat does nothing to increase cooling capacity and your engine oil will take longer to get up to operating temperature. Removing the thermostat altogether might increase coolant flow, which might increase cooling capacity, but then your engine oil would take even longer to come up to temperature.
With all that said, rather than controlling both fans from a single switch, it would make more sense to control one fan with a low temperature set-point switch and the other with a higher temperature switch. Sequencing the fans this way would save electrical power and only run the second fan when needed.
BTW, I'm using the AdvMachines fan kit and had no issues in Fish Canyon/49'er Escape near Ballarat/Death Valley at 100 F plus heat. 1st and 2nd gear in sections.
KTM '08 690 RFR, '08 990Adv S (carbs), '07 640Adv, '03 540EXC, Ducati 851, Moto Guzzi 850 Lemans, Ercole & 2VT and Yamaha RD350.
BillyD screwed with this post 01-15-2013 at 04:29 PM