function of oil temp sensor on fa20?

[jcw99]

What does the ECM do with oil temperatures given to it by the sensor on the front of the block. I know from school that coolant temperatures are used to decide when engines go from open to closed loop, fan activation and probably other things, but don't know about oil temps. Thanx!

[mav1178]

There's many engineering reasons, I'm guessing it's because Subaru chose to use 0W-20 oil for fuel economy reasons, and they need to keep the oil temps in check because 0W-20 may not give the proper fuel pressure at high temps.

So in other words, there may be some type of failsafe built in to the factory ECU map when oil temps rise above a certain amount.

-alex

[jcw99]

Thanx

[kch]

From what I understand, the ECU will start to pull timing above a certain temp (260F? not sure).

[guybo]

It won't pull timing at that low of an oil temp. The oil has to run at or slightly above boiling temp in normal operation to boil off water condensation in the oil.

I was driving home this morning having fun running the revs up cruising and noticed my oil temp get up to 233°F! These things run pretty hot.

[Spartarus]

Originally Posted by guybo

It won't pull timing at that low of an oil temp. The oil has to run at or slightly above boiling temp in normal operation to boil off water condensation in the oil.

I was driving home this morning having fun running the revs up cruising and noticed my oil temp get up to 233°F! These things run pretty hot.

That is a myth. It is incorrect.

See vapor pressure. See Raoult's law in the context of non-ideal mixtures.

You do not need to reach boiling temperature to evaporate water.

For simpler, less scientific explanation: A puddle doesn't boil when it dries up, yet when energy is added to the system, all of the water evaporates.

That's why thermostatic oil coolers are all set lower than boiling. The viscosity of your oil is only rated to 100 degrees C. After that, viscosity decreases rapidly, variations are based on composition.

[mav1178]

Originally Posted by guybo

It won't pull timing at that low of an oil temp. The oil has to run at or slightly above boiling temp in normal operation to boil off water condensation in the oil.

I was driving home this morning having fun running the revs up cruising and noticed my oil temp get up to 233°F! These things run pretty hot.

233F is not hot at all for purposes of a street car, just FYI.

Normal temps without an oil cooler can get up to 125C+ in a street car. Roughly 255F+

-alex

[steve99]

@guybo unless you work as an engineer for subaru/toyota you dont know whats been done in ecu coding. While no oil temp vs ignition retard tables are defined in opensource or ecutek brzedit ecu definitions it does not mean it does not exist.

The ecu does pull timing for high iat and has tables to pull timing for coolant temp.

It extremly unlikely that an OEM manufacturer is going to waste money installing a oil temp sensor and connect to ecu then not use it for something.


regardless of if the ecu reduces power on high oil temps, and i would be very surprised if it doesnt, you want to keep your oil temps below probably 230F especially if your running 0w20 oils at continuous high speeds and loads.

you might want to look at this data from these cars and the general trends in oil pressure as temp rises.

oil temp vs pressure data from hard use 0W20 vs 5W30
http://www.ft86club.com/forums/showthread.php?t=91820



mr perrin suggests ecu does reduce hp on high oil temps but i would like to see the iat as well


http://blog.perrinperformance.com/pe...-s-oil-cooler/




an oil cooler is a very sensible addition on these cars should be mandatory for and FI and most people who drive hard in hot climates even with a stock car should consider at least the OEM forester type oil cooler especially if you want to run the 0w20 oils.

[guybo]

You're right, I'm sure they do- just not at 100°C. It has to be a lot higher. I misread 260 as 160.... I was thinking WTF, really?

sorry, my bad