Date: Thu, 24 Jan 2002 22:22:35 -0600
Reply-To: Stan Wilder <wilden1@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stan Wilder <wilden1@JUNO.COM>
Subject: Re: '80 Westfalia-- best way to drive over passes
Content-Type: text/plain; charset=us-ascii
Being somewhat of a cynic I installed two oil temp gauges (just happened
to run a shielded six wire bundle).
The first gauge was to the sender in the oil sump plate with the VDO
gauge and sender from Bus Depot. The second sender was mounted in the oil
pressure bypass port using an Audi 5000 sending unit and OEM Audi gauge.
(second gauge now removed)
Historically I got temperature differentials of ten to twenty degrees
from the two locations.
At highway high temperature operation the oil temperatures about balanced
within ten degrees but after a forty five minute (from cold) town run the
sump plate sender read 20 degrees higher temperatures than the bypass
port sender.
The overall temp was about 200 in city driving. The overall temp for
highway driving got as high as 266 degrees in very heavy loading (70-75
mph and accelerating up hills and fighting head winds). Under normal
highway driving I managed to keep moving at 65-70 mph and maintain a 220
degree reading.
If you just reduce your speed or otherwise un burden the engine cool down
from highway operating temperatures requires about thirty + minutes to
loose 40 degrees of temperature from the oil.
If the vehicle is stopped and the engine is off then the cool down cycle
is shortened to about 20 minutes to loose 40 degrees.
This idiot method of testing was done when outside ambient temperatures
were at about 90 degrees.
I evaluate reducing engine burden just as effective as spinning the fan
faster and in effect fewer explosions in the chamber less heat.
There are certainly times when having the engine at peak torque (4200
rpm) is preferable to slowing down and effective use of the capable
gearbox is dictated to maintain the peak power range required to climb
hills.
You won't be seeing any rocket response from an oil temp gauge since the
oil temperature is slow to build and long to reduce.
Cylinder head temperature reading is more responsive and will give fairly
accurate readings within three to five minutes.
How the two gauge readings truly relate is still somewhat of a mystery to
me. I can run 380 CH and 204 oil temp. Conversely I can run 350 CH and
240 oil temp.
In most of my trips that are 130 miles straight down an Interstate my
gauges all settle in and seldom move; the oil pressure 50-55, oil temp is
220, cylinder head temp 350/360, volts 14.
If the situation changes as in fighting head winds or climbing long
inclines the first reading to change is the CH temp. I may be well past
the hill and starting a new one before the oil temp even wobbles out of
temperature changes that took effect and are currently reversing.
So I've got to go along with Bob Donalds in his statement that Gauges are
mostly toys of a sort and too much dependance on the insignificant
changes in the readings is just unneeded stress.
In the one event in seven years when I blew #3 ring lands and badly
scored the cylinder while running 85 MPH against a head wind, I saw the
oil on my back window five minutes before it showed up on the idiot
light. I didn't have an oil pressure / temp gauge or cylinder head temp
gauge at that time but I'm sure I'd have seen excessive oil temperature
and CH temp before I ever pushed it that extra little bit that blew the
works. I drove 250 miles back home by adding a quart of oil every 35
miles. I lucked out and did not ruin the whole engine.
Stan Wilder
83 Air Cooled Westfalia
On Thu, 24 Jan 2002 21:22:08 -0500 Robert Donalds <bostneng@FCL-US.NET>
writes:
> the man from historic, walkable Mount Olive, NC, wrote
>
> This whole notion that the "ENGINE ACCUMULATES HEAT OVER TIME" is
> nuts.
> If it were true that THE ENGINE ACCUMULATES HEAT OVER TIME in some
> sort
> of linear progression, every long trip would end in a meltdown.
>
> Dear Matthew
> It is so very nice to have you back on the list I have missed you.
>
> My point was that the engine takes time to fully warm up .A run up a
> long hill 10 to 15 miles would not in it self be enough to over heat
> a cold engine but could over heat a hot engine that has been driven
> for an hour or more and send it into thermal overload. It is a
> linear progression the load (speed and incline) air temp and time
> driven are some of the variables that determine if a long a long
> trip ends in a melt down. It happens all the time and I know I get
> the phone calls almost every day from the unlucky ones that did not
> know these facts
>
> Mr. bulley also wrote
> It is only when the driver places an exceptional load on the engine
> (full throttle under heavy load), while keeping the cooling system
> in a
> sub-optimum range (I.e. 3,000-4,000 rpm) that heat builds up. The
> crank
> speed is insufficient to push enough air across the cooling surfaces
> to
> displace the heat; only then does "engine heat accumulate over
> time".
>
> Mr. Bulley
> I owned a 1981 air-cooled vanagon with and had a 86 dash with a tach
> installed and I can assure you that the van ran at 4000 rpm at 71 or
> 72 MPH and I consider this a max sustainable RPM I can also tell you
> that the revlimiter built into the ECU had a max RPM of 5125 and it
> would cut the engine out at that point. Here in the north east in
> the cooler weather it can take most of an hour for the van to reach
> a decent oil temp and then only at highway speeds.
>
>
> MR. Bulley continued
> Using our current Vanagon Westfalia (4speed manual on a 2.0 l stock
> box)
> as an example... on encountering a hill, if you reduce your speed
> to
> about 45-48 mph, and put it in 3rd, you have used the transmission
> and a
> reduction in speed to reduce the load on the motor. You've made a
> mechanical exchange, sacrificing time, and distance to essentially
> reduce the pressure required at the crown of the piston. The motor
> spins
> faster, under much lighter load to move you more slowly. That's the
> idea
> behind a transmission.
>
> Matt
> I wish it was true that changing gears reduced the load on the
> engine. Changing gears and going slower does the make the engine do
> the same amount of work. the only exception to that is going slower
> does reduce wind resistance and that does not amount to much at 55
> MPH or under
>
> Matt also said
> In actuality, once your motor reaches operating temperature, the
> engine
> is constantly shedding heat. With its deep fins, alloy
> construction,
> oversized fan, and huge oil cooler it has a finite capacity for
> shedding
> heat, however, that capacity exceeds common usage by a wide margin.
>
> Mr Matt
>
> I wish that was true but between the NEW fuels, the almost universal
> lack of proper tuning plus the loads (speeds) people insist on
> putting on these poor air-cooled vans I can tell you that's its not
> the case that there is a wide margin of cooling capacity. if the oil
> temp is hitting the 250 F 270 F range then the heads are at the
> point where the NEW fuel cant hack the load so to speak. I have
> done the autopsy to many times when the proud new owner of a 2.0
> air-cooled van tried to treat it like a V8 and its not.
> The air-cooled engine does not have a narrow operating temp range as
> does a water cooled engine most gauges are very slow to react and
> because of that you wont see the wide range of head and oil temps
> your Thoughts on this are always appreciated.
>
> from walkable Wayland Ma
>
> Bob Donalds
> Boston Engine Exchange
> all rights reserved
>
>
>
>
>
>
>
>
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