LCP

I've heard several folks here say that it is good to get the oil temperature over 212F (the boiling point of water under normal atmospheric pressure) on a regular basis to dissipate any water in the oil system. But, with the exception of oil sitting in the oil pan (which isn't as hot as the stuff circulating throughout the engine anyway, correct?), the oil system is pressurized, so the boiling point of water would be much higher than 212F, correct?

xr4tic

After that, there's no pressure.

Oil coming out of the turbo would be pretty hot, and it's no longer pressurized.

Of course, if you don't get the water vapor out of the crankcase, then it will just fall back into the oil.

How much water can there really be though? You're more likely to have gas and combustion by-products in the oil than water.

ex-quattro PETE

And if it truly is 212F, then I'm in deep **** cause my engine NEVER gets this hot. It barely hits 200F on a warm sunny day. During winter it stays around 185F. However, I had my oil analyzed not too long ago, and it didn't show anything abnormal such as water.

cuatrokoop

"After that, there's no pressure."

"it's no longer pressurized."

It is definately under pressure, the pressure is that of its surroundings (atmospheric, partial vacuum due to the breather system, whatever). Depending on what sort of measurement technigue used you will either get a "gauge" reading or an "absolute" reading. Abs. readings are much preferred to gauge when it comes time to use various formulae in engineering that are functions of at least pressure. Its also why there is psia and psig in the USCS vernacular, and why in SI we use (abs) and (gauge) subscripts.

Don't make me track down my Fluid Dynamics prof and turn him loose on you ;-)

Otherwise, I agree with your statement...

xr4tic

as compared to atmospheric pressure

201-A4

Hey, cuatrokoop whats your major?

cuatrokoop

that is true, an abs. value would be something less than 101kPa at that point, not sure what the breather system actually runs at? If I get bored, I may run a tap somewhere on it...

cuatrokoop

I'm going into the dual level 400/500 classes in each as of next year (my last). Technically I'll have just a BSE in Interdisciplinary, but am trying to talk the ME dept. into allowing me an ME minor. One class I didn't take in ME may keep that from happening, just depends on how a certain associate head feels the day I talk to him...

hurricanesteve

do the trick...actually lowering the boiling point of water.

of course if any of the water molecules can find themselves a toluene molecule, then they'll vaporize quite a bit sooner

the amount of water in the oil has to be fairly low to begin with...what are the ways it can get in (except catastrophic or accidental issues):

1) condensation from air entering pcv system when the motor is cold

2) small amount entrained by oil on cylinder walls and when blowby (no ring seals perfectly, but this has got to be miniscule) gases (h2o is product of combustion) contact oil.

3) ???

Perpetual Novice

The boiling point for a mixture of Toluene and Water is 184F (at atmospheric pressure) much lower than the boiling point for water alone or Toluene alone.

So that could be where the 185F number came from.