Date:         Fri, 21 Jun 1996 18:09:29 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         DOUGLAS <douglas@bigpig.pig.net>
Subject:      Re: 2nd Oil Cooler...(Long-ish)

James Burns wrote:
> 
> >> 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.


And Douglas wwrote back;


Just an old habit ;>) I try to answer all the questions I can think of.

 
> 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.


I must disagree. Carnot's equation states that the higher the engine temp the 
more efficient the unit. Work is work. If I push my split with a 36 hp at 60mph, 
when I replace it with my new 1600 DP 65 hp unit, I still only draw 36 hp (if 
that) to push it at 60 mph. Why would a larger engine run hot pushing a lite 
load? The engine will coast along at 40-50% load and should run cool. If not, 
you got a problem beyond an oil cooler;>)
 
> 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

The point I try to make is that VW did a pretty good job designing these things. 
Most people try to use water cooled thinking on an air cooled beast (said 
lovingly:>) VW's run hotter than water pumpers, period.

I run elephants too. Never overheat.

If you still have your scoops, put 'em back on. They really help.

I may have missed it but I thought the problem was with a stock engine. When you 
start field engineering mods you open a hole new (and real big) can 'o worms.

Have fun

Douglas