Date:         Sat, 11 May 1996 23:18:15 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         jwakefield@4dmg.net (john wakefield)
Subject:      Re: aftermarket instrumentation

John Sweet asked about metering input:

  You asked "Any suggestions?"  I surely do have opinions.  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.
  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!  They get an F in applied thermo 
engineeering.  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.
  Other than for the motor temperature, VW bus applications are pretty 
much standard stuff unless you have the RV package.  In the RV Westfalia 
package, nearly all have just one battery to run evening lights, stereo 
for hours (some fall to sleep with them on),  13" combined TV/VCR (same 
sleep comments), all night people-cooling fan or fans (one up, one down) 
for  hot weather sleeping, and what ever you care to connect.  Second 
battery installation indicates RV aware ownership.
  Comes morning departure time, and that single battery may not have 
enough charge left to restart your motor.  Not a happy moment.  The meter 
you need here is a special RV 12 volt battery meter.  What's special is 
the scale spread.  A fully charged lead-acid "12 volt" battery runs 12.72 
volts after a full charge and stabilizing period.  You don't get down to 
11.5 volts measured at no load before that battery is virtually dead.  
Not enough power left to pull your hat off your head when you want to 
crank your motor against internal friction and compression.  So you use 
the RV scaled 12 volt battery to monitor battery charge.  Some are even 
displayed as percent of charge, rather than force you to post a 
conversion chart and decode the battery charge state implication.  These 
are very informative meters.
  Well, this is food for your decision process engine.  Hope it's not 
just a rehash of all the other stuff you've encountered.

  My opinions only, but they reflect considered thought.
  
  John Wakefield