My 1970 gasoline 250 Sedan Mercedes car has an electric aux fan too ...in
front of the radiator.

and of course...
you can increase coolant flow ( like more tubes in the radiator )
OR you can increase air flow through the radiator ..
to increase the heat removing abilities of the cooling system.
or both.
( you can also help the heat -removing qualities of the coolant mixture too
....water wetter for example )

here's cheater or augmenting  system I always wanted make...
use the  rear heater core under the back seat ...
and duct it's exit air overboard right beneath the van.
that would add the odd 4 % increase in total heat removal, or so I'd think.

Don't be worried if you coolant temp gets up to even say, 200 F in extreme
conditions..
as long as it comes back down going down the other side of the hill, or back
on the level...
that's not a problem, it's even normal. Maybe even 205.

Scott
----- Original Message -----
From: "Tom Hargrave" <thargrav@HIWAAY.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Sunday, April 25, 2010 6:58 PM
Subject: Re: Water Cooler System Design Flaw Workaround?

> David,
>
> Your logic is flawed - you are considering instantaneous and not
> continuous
> heat transfer. The coolant is circulating and heat is being continuously
> pulled off through the radiator.
>
> The real question should be - if you could figure out how to push 20% more
> air through the radiator than you are now, how much additional heat can
> you
> continuously pull out of the system? Would the answer be 20% more or
> something less? I can't answer that question but maybe someone else can.
>
> BTW, this is exactly what Mercedes did in the 1987 300SDL I own. There is
> a
> cooling fan mounted in front of the engine then there is an auxiliary fan
> mounted in front of the radiator. The aux fan comes on under 2 conditions
> when the A/C compressor is on or when a high temp sensor screwed into the
> engine coolant circuit comes on.
>
> And I can say that the aux fan works very well. I've been idling in 100F+
> temperatures, watched the engine temperature climb to 110C then drop back
> down to 95C after the aux fan came on. And no, my fan coupling is not bad.
> I
> originally though so and replaced it with a new one. I also checked to
> make
> sure the fan was pulling plenty of air through the radiator and it was.
> The
> aux fan pushed even more air through the radiator.
>
> They've used this system since at least the late 60's, maybe earlier. At
> least everyone I've owned except for the 50 had a aux cooling fan that was
> switched on the same way.
>
> Tom
> www.towercooler.com
>
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
> David Beierl
> Sent: Sunday, April 25, 2010 3:01 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Water Cooler System Design Flaw Workaround?
>
> At 01:22 PM 4/25/2010, Jake de Villiers wrote:
>>When approaching the long (15 - 30 minute) second and third gear grades
>>through Eastern Washington and Idaho you'd turn on the fan before the
>>rad got too hot.
>
> Ok, I see the idea.  But do the numbers make sense?
>
> Lessee... at 75 horsepower output and 1/3 efficiency the engine's going to
> be putting out something like 200 kw of waste heat, or 3.4 kWh per minute.
>
> 18 quarts of 50/50 coolant weighs around 36 lb and has a specific heat
> capacity of roughly 0.85 BTU per lb per deg F at working temperature.  So
> changing the entire coolant by 20F would get you
> 0.85 x 20 x 36 = ~600 BTU, about what a sedentary human throws off in an
> hour.
>
> 600 BTU = ~0.18 kWh.  3.4 kWh x 0.18 x 60 = ~32
>
> So a twenty-degree change in the entire coolant would absorb the waste
> heat
> of the engine for about thirty two seconds.  I think this is conservative
> since the coolant inside the engine won't be participating in this, and
> because 75 hp may be conservative for climbing a steep hill.
>
> Somebody check my numbers.  If this number is anywhere near correct I
> don't
> think it's worth the hassle.
>
> Yours,
> David