Date:         Thu, 24 Jan 2002 21:22:08 -0500
Reply-To:     Robert Donalds <bostneng@FCL-US.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Robert Donalds <bostneng@FCL-US.NET>
Subject:      Re: '80 Westfalia-- best way to drive over passes
Content-Type: text/plain; charset="iso-8859-1"

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 
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