Oil Temp - How is it measured?

[Redd]

According to OBD2, the E9x M3 actually doesn't have an oil temp sensor. It has a water temp sensor.

So, how is the oil temp on the gauge measured? Any idea?

[BPMSport]

It does have an oil temp sensor in the oil level sending unit.

Oil temp isn't an OBD II specific function.

[jcolley]

Agreed, oil temp comes from the oil sensor in the pan, that way it knows bulk oil temp.

[deansbimmer]

Check out this document. It'll explain all you ever wanted to know about the oil condition sensor (which collects the oil temp data).

http://www.meeknet.co.uk/e64/oil-sensors.pdf

[Helmsman]

Originally Posted by deansbimmer

Check out this document. It'll explain all you ever wanted to know about the oil condition sensor (which collects the oil temp data).

http://www.meeknet.co.uk/e64/oil-sensors.pdf

Thanks Deansbimmer. All these wonderings about why the temp meter should be a mix between oil and water temp is finally clarified in detail..

Doesn't say anything about the sensor's need of time in order to generate a value (other than when replaced/module re prog'ed)). To me suggest the oil level Carly gives soon as ignition is on could be true, and if so quite helpful. Thoughts?

Thanks

[deansbimmer]

The oil sensor knows if there is oil in the crankcase sufficient at least for "short term engine start". The system does not display a reading immediately after startup as not only will the sump level decrease as oil is distributed withing the block and takes time to calculate level averages, but also due to condensates within the oil that hamper accurate readings until they're burned off. Therefore the system waits for as long as needed for consistent/accurate measures before displaying on the screen. Some cars read within seconds, some take many minutes- it depends on each situation.

If Carly reads an oil level before it's shown on the iDrive, I would assume that it is interpreting the raw sensor reading, but that is only my educated guess.

[Helmsman]

Originally Posted by deansbimmer

The oil sensor knows if there is oil in the crankcase sufficient at least for "short term engine start". The system does not display a reading immediately after startup as not only will the sump level decrease as oil is distributed withing the block and takes time to calculate level averages, but also due to condensates within the oil that hamper accurate readings until they're burned off. Therefore the system waits for as long as needed for consistent/accurate measures before displaying on the screen. Some cars read within seconds, some take many minutes- it depends on each situation.

If Carly reads an oil level before it's shown on the iDrive, I would assume that it is interpreting the raw sensor reading, but that is only my educated guess.

The Carly parameter is indeed called something like "raw oil lever". It shows immediately and stays at the exact same value during the drive. Obviously you're right the level will go down once the oil is distributed, I'll check this again from pre start and see what comes up.

Thanks

[kerrit]

with a thermometer

[Redd]

Originally Posted by kerrit

with a thermometer

Did you have to go to college to learn this?

[Helmsman]

Originally Posted by deansbimmer

The oil sensor knows if there is oil in the crankcase sufficient at least for "short term engine start". The system does not display a reading immediately after startup as not only will the sump level decrease as oil is distributed withing the block and takes time to calculate level averages, but also due to condensates within the oil that hamper accurate readings until they're burned off. Therefore the system waits for as long as needed for consistent/accurate measures before displaying on the screen. Some cars read within seconds, some take many minutes- it depends on each situation.

If Carly reads an oil level before it's shown on the iDrive, I would assume that it is interpreting the raw sensor reading, but that is only my educated guess.

Just to follow up on this Deansbimmer, hooked up Carly already before engine start. Presented the oil level and kept the exact same after start up. Assuming it takes it from the level sensor, don't believe there is anywhere else to get it, I'd guess its not more accurate then so? Top off with say 0.5 liter immediately makes a difference on Carly though. Any ideas about what volume oil actually is distributed during run? (except for the filter can).

Cheers