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Discussion Starter #1
My new (to me) 2006 S4R is running quite cool; 150s when ambient is in the 60s, and 160s when ambient is in the high 80s. Shouldn't this be running at or near 180 when the engine is warm?

I'm getting about 40mpg, so it doesn't seem to be running excessively rich.
 

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Old Wizard
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Coolant Temperature

As a comparison, on a day with 75°F ambient air temperatures, coolant temperatures in my '95 916 reach 140 - 165°F.

The 916's cooling system is designed to keep the engine coolant temperature at 175°F (80°C) when your moving at speed on a 90°F day. This operating condition is used to size the radiator, water pump and hoses. On cooler days, and/or with a lower percentage of glycol in your coolant you should expect lower coolant temperatures.

When you let it idle, when the coolant temperature goes above 200°F, a temperature sensor will signal the cooling fan to start, and it continues to run until the coolant temperature drops to 190°F. Since your bike only reaches a reading of 160°F then you should suspect that your temperature gauge is reading a little low.

Hans-Henrik on this List noted that when he measured his coolant temperature and compared it to his 888 gauge reading that the gauge read 9-18°F too low. My guess is that all Ducati temperature gauges have a similar accuracy.

Certainly you have a right to be concerned. 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. Most stock bikes are designed to produce their best power when coolant temperatures are around 200°F.

The bike's computer uses the engine coolant temperature sensor (not the gauge 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°F. So from a fuel correction standpoint, the proper operating temperature is above this. Reduce the coolant temperature too far below this and you're not operating efficiently.
 

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My new (to me) 2006 S4R is running quite cool; 150s when ambient is in the 60s, and 160s when ambient is in the high 80s. Shouldn't this be running at or near 180 when the engine is warm?

I'm getting about 40mpg, so it doesn't seem to be running excessively rich.
On the highway mine runs at about 75-77 degC (ambient ~20 degC). On the streets 85-90. Its roughly the same as yours.

I have the full DP Termi, and do some 16 km/L (40+ mpg) doing 150 km/hr.
 

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Discussion Starter #4
Good answers, thanks for the info/insight.

I suspected an inacurate gauge reading, since the fuel consumption is pretty good (got 45mpg this last tankfull:)), and since from experience, I know that the speedo is off by around 10%, more as the speed increases - I think that the EU laws regarding pessimistic readings requiring the vendor to pay the fine, so a little CYA in the optimistic direction saves $$.

When I had a Multistrada, the bike ran best when very hot (oil temp readings around 220-230) and terrible when cool - every time it rained, or when ambient temp dropped below 50F. That's one of the reasons I went for the S4R believing that water cooling would provide a better 'year round solution.

randy
 
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