A bike should get up to temperature for best performance.
Duane Mitchel reported that he ran a series of tests to establish optimum running temp for a race bike and found that (185F) 85ºC was about perfect. Over that, they lost horsepower fairly quickly (down about 15 HP at 100ºC) and below that the same (down about 6 HP at 65ºC).
The computer uses the engine coolant temperature sensor to supply additional fuel while the engine is warming up. Engines need more fuel when for a cold start as there is no heat in the ports and chambers to keep the fuel atomized as vapor, so it condenses. Fuel as a liquid burns very badly in the combustion chamber, so throwing more at it ensures enough stays as vapor for some sort of combustion. Injected engines get a very nice fuel spray from the injectors and this is why injected engines behave better when cold.
In the Ducati system, the sensor tells the ECU to stop warm-up fuel enrichment at around 175°. So from a fuel correction standpoint, the proper operating temperature is above this value. Reduce the coolant temperature below this and you're not operating efficiently.
So cooler is not better from an operating perspective. YOU may feel more comfortable, but the bike is not operating at an optimum point on its fuel map.
In particular, I had to remove the water plus Water Wetter mixture from my 916's cooling system because it was running too cool.
On a day with a 75°F ambient air temperature, coolant temperatures would only reach 140 - 170°F (60 - 75°C.) I tried blocking off air flow to a section of the radiator, but temperatures still stayed below the gauge midpoint. At these temperatures, the ECU is still adding extra fuel for warm-up conditions (below 175°F.) The tailpipes were black from an overly-rich mixture and gas mileage was down.
18-Jul-2005, 13:10 
antonye
Linear Mode
