Date:         Fri, 21 Jun 1996 12:02:25 -0800
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         jburns@mail.sdsu.edu (James Burns)
Subject:      Re: 2nd Oil Cooler...(Long-ish)

>> First David wrote:
>>
>> >> Most people I know who have coolers in their engine compartment have the
>> >> hot side of the cooler routed out through the floor of the engine
>> >> compartment, which takes care of that problem.
>> >
>> Then Douglas wrote
>> >
>> >If you do that you could be robbing air from the engine cooling system.
>> >Other components could run hotter ;>)
>> >
Then I wrote:

>> Douglas, I'm going to have to put some of the weight of "book learnedness"
>> behind David. The air inlets on any year VW are oversized for their purpose
>> of admitting air to a stock engine. If that weren't the case, one would
>> hear a lot of turbulence-induced noise from that location at higher fan
>> speeds. The tiny passages between cooling fins are the real culprit in
>> limiting airflow, especially at high air velocity. Making more outlet area
>> should only help. The pressure drop in the engine compartment due to the
>> extra flow from the extra fan and outlet duct will be very small.
>
Then Douglas wrote back:

>The engine compartment runs with a DEPRESSED atmosphere. If you merely put
>a hole
>through the engine compartment and put the cooler into it, air flow will be
>inward; preheating the cooling air. If you put a fan on the unit to pull
>air from
>the engine compartment, you depress the atmo. more and reduce cooling. Just
>opening the window vents makes a 10 deg diff in engine temps due to air flow
>changes!
>
I had also written:

>> This same principle is true for the flow of gases through the engine
>> itself: big carburators and high-flow heads are wasted if a decent set of
>> headers (preferably tuned) aren't used.
>
Douglas wrote:

>But a stock engine does not need any additional cooling. And just because an
>engine is bigger does not mean it runs hotter. Its still pushing the same
>LOAD.
>No more energy is needed to push the load it under like conditions.
>
>If he still runs hot he's probily using cheap fuel and to much timing,
>maybe to
>lean on the carbs. Something else is wrong other than cooling.
>
I had also written:

>> And for those who don't trust over-educated types, if I remember my
>> inspection of Rev. Hoover's Grendel, it has the bottom-ducted internal fan
>> arrangement. Nuff Said.

We all agree:
>> >> >If you put it under the van, it will get wiped off the first time
>> >> >you go over something in the road.

My response and Question now is:

Always implied if not stated was that a secondary (electric) cooling fan is
used to push air through a deck mounted cooler and out the bottom. Without
the fan, air comes through the hole into the compartment.

Granted, the use of additional oil cooling is often a treatment and not a
cure for the usual causes of overhreating: bad gas/mixture/timing, air
management, low oil, fan problems, etc. but I disagree that a bigger engine
will not run hotter. Increasing engine displacement without beefing up the
cooling system is a bad idea. Even if the stock and enlarged engine are
pushing the same LOAD the bigger engine is almost always going to have
poorer efficiency at the same speed (eg. gearing). This inefficiency leads
to heat production.

All that aside, cylinder head temperatures of enlarged VW engines seem to
be the killer, not oil temp, and the two do not increase at nearly the same
rate. Roasting heads may not show up as a large increase in oil temp.

Question: given that wing vents cause 10 degree F increase in temp, what
are my elephant ear mirrors doing. Also, are the aftermarket inlet scoops
the PO took off my splittie worth putting back on?

Regards, Jim

Dr. Jim Burns
San Diego State University
5500 Campanile Dr
San Diego, CA 92182-1323
619.594.6076