Join Date: Feb 2007
Location: San Diego, CA, USA
Engine Warm-Up Period
The main reason that you allow a warm-up period is to let the engine get warm and help vaporize the fuel. Until then, you'll get more misfires from incomplete combustion. So as soon as the bike will take throttle smoothly there's no reason to continue warming up — it’s ready to ride.
From a lubrication point-of-view, the worst condition for wear is when the engine is cold. At startup, the only thing protecting against metal-to-metal contact is a residual thin film of oil. (Synthetic oils have better film strength, BTW.) So when you start the bike, avoid revving the engine excessively while the oil pump begins to send oil through the oil galleries. This can take a couple of minutes in Ducati engines. After this, you can ride immediately (at moderate engine speeds, of course) but you should wait for normal operating temperatures before booting-it.
We know that an engine should be at its design operating temperature to make good power. Operate at too low a temperature and the engine is less efficient and makes less power. Higher temperatures are more thermodynamically efficient, but run at too high a temperature and you exceed the thermal expansion design basis of critical components and raise fuel octane requirements that can cause engine knock. Ducati’s use engine management computers incorporating a coolant temperature sensor to retard the engine ignition timing enough to compensate for any increase in octane requirement when operating temperatures increase.
In the Ducati system, the sensor tells the ECU to stop warm-up fuel enrichment at around 65°C. On bikes made before 1995 or so, it was at 85°C. So from a fuel correction standpoint, the proper operating temperature is above these values. Reduce the coolant temperature below them and you're not operating efficiently. The engine will be running too rich.
Duane Mitchel reported that he ran a series of tests to establish the optimum running temperature for a race bike and found that 85ºC is perfect. Above that , you’ll lose horsepower fairly quickly (down about 15 hp at 100ºC) and below that the same (down about six hp at 65ºC).
In cold weather, the trick to temporarily getting back to the best engine temperature for performance and economy is to make the radiator effectively smaller; by preventing the cooler air from reaching a portion of the radiator’s cooling fins, thereby reducing it’s cooling capacity. You cover a portion of the radiator to reduce cooling air flow and raise the coolant temperature. How much radiator area you cover depends on how low an ambient air temperature you expect. Trucks in arctic climates, for example, will run with 90% of their radiator covered.
Last edited by Shazaam; Jan 8th, 2016 at 10:45 am.