Date: Mon, 15 Jul 1996 15:26:32 -0400
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: SyncroHead@aol.com
Subject: Wasserboxer cooling (was:Re: aftermarket instrumentation)
In a message dated 96-07-13 00:06:49 EDT, jwakefield@4dmg.net (john
wakefield) writes:
>The number
>one VW water cooled motor killer in bus installations is their inadequate
>implimentation of water cooling. They cool well enough at any speed from
>5 mph up to about 10 mph less than their top speed, but at the extreems,
>they often don't cut the mustard. So, the top thing to monitor in my
>opinion is engine heat.
While I agree that monitoring engine heat in any engine is a high priority, I
don't know why you continue to go on about cooling problems in the
wasserboxer motor. BTW do you own one of these motors and have first hand
experience with it?
As for the cooling problems, I haven't had any that were not traced to the
failure of a specific item. I once had a thermostat stuck open in my 87,
causing the engine to run too cool and the heater to provide inadequate heat.
I don't recall any cooling problems on the list that were tracked to "design
flaw". If it were a design flaw, it would be showing itself in my vehicle as
well - it is not. I do recall reading about problems that were attributed
to: A)stuck thermostat, B)restricted radiator, C)combustion leaking into
coolant, and D) owner failing to notice coolant leak and having too little
coolant in the system. These are all problems that can and do affect all
water cooled engines.
Can you site any examples to the contrary?
My recent experience tells my general experience with these engines and their
cooling systems. Last monday I traveled through the California desert in the
middle of the afternoon. I had a luggage rack & luggage on top of the van as
well as three bicycles. This created a considerable wind load! Inside the
van I had 2 overweight adults, 2 kids, and camping gear (including 3 heavy
icechests) packed everywhere there wasn't people. This was a lot of weight!
The outside temperature was around 100 deg F. We were facing a stiff
headwind and alternately drove up mild inclines and on flat sections. The
elevation was about 3,000 ft. I ran the engine at about 4,000 to 4,400 RPM
(trans in 3rd gear) for about 2 hours straight under these conditions. The
coolant temperature NEVER got above 2/3 the way up the gage - it normally
rides at 1/2 gage travel. I did NOT turn on the heater to help cool the
engine. We had the A/C ON for much of the trip - I prudently turned the A/C
off while we were on ascending grades, but it was on enough to keep us comfy
inside. My cooling system is completely stock.
I expect that you'll say - "Ahhh, that's only coolant temperature, What
about the oil temperature?" It is true that presently I am not able to
monitor oil temperature. Oil temperature can be much more volitile than
coolant temperature, but after a sustained period under extreme condiditions
the coolant temperature will inevitibly rise if oil temperature remains very
high. This would have been refelcted on the coolant temperature gage before
long & it wasn't.
> The difficulty in this is deciding where. Let me tell you where it
>would be stupid to monitor it: at the radiator. With those long,
>undersized-for-their-length, twisty coolant lines, inadequate water pump
>flow at top and low/parked speed, and their common tendancy to get "air
>locked", 20 to 50 degrees difference may exist between the radiator and
>the worst in the motor block!
VW has mounted it's coolant temperature sensor for the temperature gage at
the engine. While it would be a bad idea to measure coolant temperature at
the radiator for instrumentation purposes, turning on & off the radiator fans
with a temperature switch here works just as well as a switch at the engine.
All VW needed to do is determine the proper engine coolant operating
temperature, and choose a radiator mounted switch with an appropriately lower
setpoint to account for the temperature loss in the hoses between the engine
and the radiator. I believe that they have done this, but perhaps a slightly
lower temperature switch would be helpful.
By what calculations have you determined that the coolant lines are
"undersized - for - their - length" ?
In my estimation these admittedly long coolant lines contribute very little
to the flow restriction in the cooling circuit, likely less than 2%, while
the engine's own passageways and the radiator's own labyrinth of passageways
contributes the bulk the restriction to flow in any system. Further, these
long hoses do two positive things to the wasserboxer's cooling system that
are not found in other designs.
1. Provide more coolant than if the radiator were close to the engine. This
additional coolant provides greater capacity for coolant to carry away the
engine's heat. An infinite supply of coolant would be ideal!
2. Provide additional surface area where air can absorb the heat carried in
the coolant. That's of course why the coolant arrives at the radiator cooler
than when it left the engine.
>They get an F in applied thermo engineeering.
And what grade did you recieve in applied thermo? I got an A and a B in my
thermo classes while earning my degree in Mechanical Engineering. BTW, I got
As in each of my fulid mechanics classes.
>If you want to measure the motor temp, it's stupid (IMO)
>to accept some measurement point cooler than the motor. Similarly, if
>you want to measure the temperature of your oil which is another
>important motor coolant, don't measure it after some oil cooler. Find
>the hottest oil temp you can find and monitor that. You NEED to know the
>worst case, not some problem concealing average or downstream location
>related only by some variable complex functional relationship. Only if
>you want to see how effective your oil cooler is, should you measure
>after the cooler for a second comparison value. You get the idea.
We have agreement here.
<Snip on battery/voltage stuff>
Regards,
Jim Davis
87 GL Syncro
88 GL Wolfsburg
