Date:         Tue, 19 Jul 2011 21:38:00 -0400
Reply-To:     Edward Maglott <emaglott3@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Edward Maglott <emaglott3@GMAIL.COM>
Subject:      Re: Watching Oil Temp (long, as usual)
In-Reply-To:  <20110719193828.W8M0N.430374.imail@eastrmwml29>
Content-Type: text/plain; charset="us-ascii"; format=flowed

I think the hottest part of the engine is in the heads around the
exhaust ports where all that hot gas is rushing past the valve and
out.  Aren't exhaust gasses 1300F+ degrees?  The bearings have
friction to produce heat but as long as they are lubricated I don't
think they get that hot.  I am curious and also appeal to those more
expert than I.

I think someone said earlier about the much greater ability of the
cooling system to moderate it's own temperature.  There is a big
volume difference, about 4 times the amount of coolant to oil, and
the big radiator and high volume pump.  As the engine gets under load
the cooling system can respond quickly and move a huge amount of that
heat to the radiator and out of the system.  The capacity of the oil
system to remove heat is much lower.  As someone else said, it's
thermostat probably goes wide open and it does what it can but the
smaller volume of oil flowing through the small cooler can only do so
much.  The oil system is designed to provide oil to bearings under
much higher pressure and at lower volume.  In general, the fact that
it gets cooled one way or another is not primary.  Many engines have
no oil cooler at all (other than the sump.)

I was changing my oil the other day and noticed how #%& hot the
filter was after my short warm up drive.  Made me wonder what the oil
circuit is like.  Sump to pump to stock cooler to filter to
bearings?  Or filter before cooler?

Edward

At 07:38 PM 7/19/2011, Dave Mcneely wrote:
>---- Rocket J Squirrel <camping.elliott@GMAIL.COM> wrote:
> > On Tue, 2011-07-19 at 13:14 -0400, Edward Maglott wrote:
> >
> > > I'm pretty sure the coolant flows through the heads and that is where it
> > > picks up most of the engine heat.
> >
> >
> > Oh -- okay. The only heads I've ever held were from an aircooled. They
> > had no plumbing for coolant.
> >
> > So on the waterboxer, where is the oil picking up the extra heat that
> > shows on the oil temp gauge but not the coolant gauge when the engine is
> > under demand?
>
>The oil is picking up heat from all parts of the engine it is in
>contact with, and that heat is reflected in the oil temperature
>reading.  The coolant is also picking up heat from all parts of the
>engine it is in contact with.  That heat is also reflected in the
>coolant temperature reading.  The two differ because the coolant
>measurement is made at a point where the coolant is cooler than the
>oil temperature.  It would actually be a rather odd system with
>absolutely equal heat distribution, especially since the coolant has
>a cooler (the radiator) to reduce its heat burden.  That is, there
>is at least one point in the cooling system that is considerably
>cooler than the heat source, the engine.  Perhaps that is true for
>the oil, also, especially if there is an effective oil cooler in the
>system, but oil is less effective at heat transfer than is coolant,
>and any oil cooler, though it might be a good one, is still less
>effective than the very large radiator.  Or, put another way, the
>engine produces heat faster than the oil and coolant combined can
>remove it, so there is a temperature gradient in the system.  The
>coolant is measured at the cooler end of that gradient.  The oil is
>measured at the hotter end.  The oil is also directly in contact
>with the hardest working, greatest heat producing parts of the
>engine, the bearings, rods, cam and so on.
>
>my thoughts.  experts may differ.  mcneely
> >
> > -- RJS
> >
> > sent from my old aircooled heads
>
>--
>David McNeely