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Date:         Wed, 20 Jul 2011 13:03:41 -0700
Reply-To:     Jake de Villiers <crescentbeachguitar@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jake de Villiers <crescentbeachguitar@GMAIL.COM>
Subject:      Re: Watching Oil Temp (long, as usual)
Comments: To: camping.elliott@gmail.com
In-Reply-To:  <1311182872.4925.152.camel@TheJackUbuntuNetbook>
Content-Type: text/plain; charset=ISO-8859-1

When I stick my hand out the window at 20 mph I certainly feel the air going by...

What kind of RPM are you using at that speed Mike? I do long steep bits at about 3200 RPM.

On Wed, Jul 20, 2011 at 10:27 AM, Rocket J Squirrel < camping.elliott@gmail.com> wrote:

> "Airstream," he said. > > Like crawling up a desert grade in 1st gear (AT) at 20 mph in 100 degree F > weather. > > > On Wed, 2011-07-20 at 10:13 -0700, Jake de Villiers wrote: > > There's some almost information in your post Mike. > > The oil pump moves the oil at a fixed rate whether cold or hot. Just like > your water pump, it increases the rate with RPMs. > > The sump, whether your finned aluminium VW one or my black painted steel > Subaru one is hanging down in the airstream for a reason. The cooling air > pulls heat from the metal surface, allowing the heat from the oil to take > its place. > > And yeah, the volume of coolant vs the volume of oil makes the temp gauge > cycles very different from one another. > > Happy motoring! > > > > > On Wed, Jul 20, 2011 at 9:10 AM, Rocket J Squirrel < > camping.elliott@gmail.com> wrote: > > On Wed, 2011-07-20 at 08:47 -0500, Dave Mcneely wrote: > > > Bottom line, I think the oil has a major heat source, and only if an > > external cooler has been added does it have a real functional way to > > dissipate heat other than to the coolant through metals that both > > contact and through such things as the sump. The sump is like a > > reservoir of liquid, it cools slowly compared to a radiator. The > > coolant has a large heat sink, and thus has a temperature gradient. > > That gradient includes the oil. > > > So what we're saying is that the oil is in contact with some really hot > bits, and because there is high thermal resistance between the oil and > the coolant, the oil can climb to much higher temperatures than the > coolant. > > It doesn't help matters that the hot oil drains down to the sump which > isn't cooled by anything except the hot pavement under the engine! > > Others have also explained that while the water pump can move a lot of > coolant up to the heat sink in the front, the little oil pump just chugs > along pushing the oil more slowly and in lower volume so that even if > there was an external oil cooler the size of the radiator, the stuff > ain't moving fast enough or in enough volume to cool the really hot bits > it's in contact with like the coolant can for the hot bits it is in > contact with. > > I think I've arrived at point where I have a better understanding of why > the oil temp gauge shows higher peak temps during high engine demand > than the coolant gauge shows -- which is the answer to my original > question! Many thanks to all who have taken the time to respond to my > inquiry! > > -- RJS > > > > > -- > Jake > > 1984 Vanagon GL 1.9 WBX - 'The Grey Van' > 1986 Westy Weekender/2.5 SOHC Subie - 'Dixie' > > Crescent Beach, BC > > www.thebassspa.com > www.crescentbeachguitar.com > http://subyjake.googlepages.com/mydixiedarlin%27 > >

-- Jake

1984 Vanagon GL 1.9 WBX - 'The Grey Van' 1986 Westy Weekender/2.5 SOHC Subie - 'Dixie'

Crescent Beach, BC

www.thebassspa.com www.crescentbeachguitar.com http://subyjake.googlepages.com/mydixiedarlin%27


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