Oil temp sensor fault? - Page 3 - Ducati Supersport 939 Forum
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post #21 of 28 (permalink) Old 11-04-2019, 09:58 AM
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Originally Posted by edufox View Post
Exactly, no coolant temp on the ECU equation to adjust AFR 😉
He has used an oil temperature sensor as the reference for engine temperature which it would be for an air-cooled engine. For a water-cooled engine swap the oil temperature sensor for a coolant sensor. The engine temperature (coolant or oil) has by far the biggest effect on fueling.

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post #22 of 28 (permalink) Old 11-04-2019, 10:20 AM
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Originally Posted by GolanTrevize View Post
Of course, what is failing is the water (coolant) temp sensor. Anybody knows if it’s easy to replace?
It's quite a shitty job.
It lays on the horizontal cylinder, on the left behind the battery. You don't need to remove the battery though.
On the coolant pump is a plug, undo that and drain your coolant into at least a 3 litre bottle.
Then you need a 17 or 19mm spanner. It has a lock tight on it so you'll struggle a bit. The connector is a bosch connector with a stainless steel clip. I couldn't undo the clip so I just pulled it off from the sensor. You might need to undo the main return feed ( top fat pipe) so you can get your hands in. Obviously it requires the left side fairing to be removed.
After you change it you'll need to top up the coolant and bleed the vertical cylinder head to get the air out.

Last edited by amoslws; 11-04-2019 at 10:30 AM.
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post #23 of 28 (permalink) Old 11-04-2019, 10:27 AM
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Originally Posted by edufox View Post
Used to think air temp sensor give temp data to the ECU to adjust AFR based on air temp, density: O2 quantity etc.
It uses the coolant sensor as well. When hot, for example after riding for an hour or so. When you want to start the engine the ecu picks up the engine temperature and determines the start up injection. If it's receiving the wrong voltage then it won't start. Believe me I've been through it this year with the SS.
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post #24 of 28 (permalink) Old 11-05-2019, 05:06 AM
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@edufox

Continuing the discussion regarding the air temperature and coolant temperature influence on the fueling.

Main ecu in the owners manual , which is the fuel management system (Bubble43) shows Pins E3 & F2 for ambient temperature and D4 & D2 for engine temperature.
My experience tells me the coolant sensor influences the fueling at start up.

Last edited by amoslws; 11-05-2019 at 05:22 AM.
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post #25 of 28 (permalink) Old 11-05-2019, 06:27 AM
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Hi Amos,

Yes, engine temperature sensor allows the ECU to manage correctly the cold start and the engine heating lapse.
It seems that in the event of an engine (coolant) temperature sensor fault, the ECU implements a recovery value of 70C and activates the radiator fans. But when normal ridding the value for ECU to manage AFR I think is air temp not engine temp, so yes, important coolant temp to cold start 👍🏻

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@edufox

Continuing the discussion regarding the air temperature and coolant temperature influence on the fueling.

Main ecu in the owners manual , which is the fuel management system (Bubble43) shows Pins E3 & F2 for ambient temperature and D4 & D2 for engine temperature.
My experience tells me the coolant sensor influences the fueling at start up.
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post #26 of 28 (permalink) Old 11-05-2019, 08:40 AM
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Once the engine is up to temperature the coolant temperature should be pretty stable at which point the air temperature would altering the A/F mix by small increments but in practice the coolant temperature on most Ducati's can vary by quite lot. There are also the MAP sensors which, with the air temperature sensor enables the ECU to determine the mass of air entering each cylinder dependent on the throttle opening.
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post #27 of 28 (permalink) Old 11-05-2019, 09:43 AM
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Originally Posted by edufox View Post
Hi Amos,

Yes, engine temperature sensor allows the ECU to manage correctly the cold start and the engine heating lapse.
It seems that in the event of an engine (coolant) temperature sensor fault, the ECU implements a recovery value of 70C and activates the radiator fans. But when normal ridding the value for ECU to manage AFR I think is air temp not engine temp, so yes, important coolant temp to cold start 👍🏻
Agreed, upto around 70C the ecu will consider the engine temp and air temp. I don't know the mapping of the SS and I'm not an ecu programmer but generally the coolant fueling correction maps seem to teeter off from 70C.
Air temp is throughout the temp range that the ecu will correct the fueling according to the AFR trim maps.
However my point was that hot starts will be an issue with a faulty coolant sensor. The cranking injection is based on the engine temp sensor.

According top the schematic in the manual the air temp sensor feeds the dashboard, then there's a second ambient temperature sensor that feeds to main ecu as highlighted in my post earlier.

Last edited by amoslws; 11-05-2019 at 09:48 AM.
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post #28 of 28 (permalink) Old 11-05-2019, 12:24 PM
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And air temperature sensor is frecuently cheated by tunned ECUs by lowering the output to achieve more gasoline in the mixture A/F.
No cheating in engine temp to cheat ECU though 🏻
No doubt, a very interesting tech issue
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