Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > 998 / 996 / 916 / 748 > Running Hot

[custard]

On a ride out to Bristol today I noticed that crawling along in traffic, and in the hot weather we are having ,I noticed the bike was running at around 95.C.
Given the weather what sort of temp sould it be at crawling in traffic on a hot day.

[955matt]

Hi,I have a 916 and in traffic it runs about 85-90 if moving slowly,sitting still in traffic it will bring the fan in at about 95-100(then fry your legs).On a normal run in the hot weather the temp is about 75-80.

Hope This is of some help.

MATT

[Shazaam!]

A motorcycle cooling system is designed to keep the engine coolant temperature at the gauge midpoint (80°C for a 916) when moving at speed on a hot day (32°C air is assumed in the calculations.) This operating condition is used to size the radiator, water pump and hoses.

Any engine should be at its design operating temperature to make good power. Operate at too far below this temperature and the engine is less efficient (Ducati's EMS causes it to run rich) and makes less power. Higher temperatures may be more thermodynamically efficient, but if you run at too high a temperature you'll raise fuel octane requirements (Ducati's EMS retards the ignition timing) and you'll ultimately exceed the thermal expansion design basis of critical components.

The temperature gauge displays the range of expected operating temperatures. If you're at speed on a warm day you should expect to see temperatures between the gauge midpoint and three-quarter point (usually 100°C for most bikes.) The maximum gauge reading indicates the boiling point of a pressurized 50/50 mix coolant, the point where the pressure relief cap will likely discharge coolant to a 916's overflow tank.

When you get stuck in stop-and-go traffic, the temperature will begin to rise because now there is reduced airflow through the radiator. At around the three-quarter point on the gauge, the radiator fan kicks-in to provide the needed airflow. The fan stays on above this temperature. With the fan operating, when the temperature drops to just above the gauge midpoint, the fan stops running.

During these traffic conditions, temperatures in the upper quarter of the gauge display should be expected and not necessarily be a cause for alarm or an indication of cooling system problems. Modern fuel injected engine management computers quickly adjust the engine ignition timing so as to run well at these higher temperatures.

You should also expect that the temperature will change often and fairly quickly because, unlike a car, a motorcycle only holds about 3-4 liters of coolant. So there's not a lot of heat stored there.

Most stock-engined sportbikes are designed to produce their best power when coolant temperatures are close to 95°C.

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 80°C. So from a fuel correction standpoint, the proper operating temperature is ABOVE 80°C. Reduce the coolant temperature below this and you're not operating efficiently.

In fact, if your engine is consistently running at 60 - 70°C in cool weather, you should probably cover part of your radiator to reduce cooling airflow.

The fact is that cooler is not better for your engine. YOU may feel more comfortable, but the bike is not operating at an optimum point on its fuel map.

For example, I had to remove the water plus WaterWetter mixture from my 916's cooling system because it was running too cool. On a day with 24°C ambient air temperatures, coolant temperatures would only reach 60 - 75°C. I tried blocking off a 4 x 11 inch section of radiator, but temperatures still stayed below 80°C. At these temperatures, the ECU is still adding extra fuel for warm-up conditions by adding more fuel. The tailpipes were black and gas mileage was down.

Those of you that own 998's should expect even higher temperatures. Typically, 998's run at around 95°C at speed on a warm day and at around 120°C in traffic. I suspect that this higher operating temperature is a result of the revised fairing cooling vents. The computer turns the 998's fans on at 101°C (LH) and at 102°C (RH).

[Shazaam!]

One thing that will cause your bike to run hotter is that the oil and water radiator fins get bent from small stones thrown by the front tyre. This closes off airflow for a portion of the radiator. The solution is to carefully straighten any bent radiator fins and then cover the radiator with protective screens.

This is an easy do-it-yourself project for a superbike. Cut a piece of aluminum window screening to fit leaving 4-5 inches on top to make some tabs to bend over the top and back of the radiator. It conforms easily to the curved radiator shape and the wind pressure holds it firmly against the radiator.

Remove the V-shaped lower front cowl and attach another piece of screen to protect the oil cooler. Fasten it to the back of the panel with small self-tapping screws and washers at the four molded holes in the panel.*Silicone adhesive or double-sided tape also works.

Any screening will reduce airflow somewhat, of course. The smaller the mesh, the more protection against smaller debris and screen-plugging insects. I can only offer that common aluminum window screen works fine in desert temperatures with no noticeable effect on 916 coolant temperatures.

I wish I thought of it right away before fin damage occurred. After 20,000 miles, I still haven't had to replace it. I used window screening simply because it's cheap to replace and has a fine-enough mesh to spread out the impact load (and keep bugs out), but if you prefer something different, check out the McMaster-Carr web site. When they sell mesh screening, they define the percent open area that tells you its ability to flow air.