From: Kim Howe <khowe@omninet.net.au>
Date: Sat Mar 30, 2002  07:05:30 AM Australia/Perth
To: FrankGRUN@AOL.COM
Subject: Re: On Longevity, Displacement, Efficiency and Technology in
Conversions

Frank, I really enjoy your posts, I wonder if you could clear up a
couple of things for me.

On Tuesday, March 26, 2002, at 02:58 PM, Frank Grunthaner wrote:

So, lifetime of any modern engine is directly related to the work you
require
that it generate during your ownership period. Period.

So, if for example the Vanagon and a Golf had the same engine, and the
same gearing, and spent most of their time traveling at 75mph, the
difference in engine life would be the relative drag (aerodynamic and
otherwise) between the two, ie if the drag of the Vanagon is 3 x that of
the Golf, and the engine will do 300,000 miles in the Golf, it will do
100,000 miles in the Vanagon? Do you know where we could obtain the drag
figures for the different vehicles to evaluate this?

  o, anyway, I decided to prepare a table that could compare the
mechanical
efficiency (and therefore engineering prowess) of the various engines
that
could power these bricks through the ether. The quantity of comparison I
have
chosen is the brake mean effective pressure developed in the combustion
chamber while doing work on the piston. The number is derived from the
peak
torque developed at the flywheel per unit engine displacement. These
numbers
are readily calculated from the meager engineering data provided by the
reclusive Subaru personnel, and are readily expanded by the addition of
your
favorite heat pump. I have arranged the values in ascending order of
higher
pressure (means higher efficiency). Pressure expressed in units of psi.
In
essence, the torque maximum represents the peak volumetric efficiency of
the
pump as well as the maximum efficiency of completely consuming the
available
fuel for air heating. This number is a function of the combustion chamber
design, the intake and exhaust manifold flow dynamics, cam and ignition
timing, etc.,etc. Bigger is better. (Also often newer.)

If I were to put an aircooled engine on a dyno and read off the torque,
I would be reading the torque including all cooling system losses. If I
were to do the same with a liquid cooled engine, I would be excluding
the drag introduced from the radiator, and probably make sure I got my
readings before the fan cut in, so I excluded the alternator drag from
that too. Did you compensate for this at all? Do you know of any way to
calculate these losses? It would be interesting to see a comparison of
the total cooling system power requirements for air cooled and water
cooled engines. I remember seeing this done many years ago, and the air
cooled won hands down, which was behind my statement that aircooleds are
more efficient (ie air cooling wastes less energy). Liquid cooling
technology may have improved enough in recent years to make this no
longer the case. (Or was the information I saw years ago in error
anyway?)

   Engine  Displacement    Torque      BMEP
                (liters)       (ft.lb.)        (psi)

   Vanagon 2.0L A/C          101@3000      126.9
   VW GX       1.8L I4        96@3000      132.8
   VW MZ       1.8L I4        98@3250      135.6
   Vanagon 1.9L WB       106@2600      136.6
   Subie 2.5   2.5L WB (<96) 144@2800      136.6
   Vanagon     2.1L WB       117@3200      136.7
   VW 9A       1.8L I4       113@4400      140.8
   VW HT       1.8L I4       105@3000      145.3
   AUDI 2.3    2.3L I5       140@4500      149.7
   VW RV       1.8L I4       109@3800      150.8
   Audi 3A     2.0L I4       121@3200      150.8
   VW ACC      1.8L I4       107@3500      150.8
   VW AAZ      1.9L I4 TD    107@2500      150.8
   Subie 2.5   2.5L WB (>97) 162@2800      150.8
   Subie SVX   3.3L WB       228@4400      150.8
   VW ABA      2.0L I4       122@3200      152.0
   VW RD       1.8L I4       110@3200      152.2
   VW AAA      2.8L I4       173@4200      152.6
   Subie 2.2   2.2L WB       137@4400      153.0
   Subie 2.5   2.5L WB P II  166@2800      157.4
   VW PF       1.8L I4       114@3800      157.7
   SAAB 2.0    2.0L I4       128@3000      159.5
   TIICO (SA)2.0L I4         132@3500      164.5
   Subie 2.2   2.2L WB P II  149@3600      166.4
   VW AHY      1.9L I4 TD  i 149@1900      193.7
   VW 1.9 TDi1.9L I4 TDi     155@1900      201.5
   Subie 2.2T2.2L WB T       181@2800      202.2
   VW 1.8T 1.8L I4 T         162@2200      224.1
   SAAB 2.0T   2.0L I4       188@3000      234.3

If there were unreported losses in the water cooled that required say 5
ft.lb torque to compensate, that would mean as far as I can see that the
2.0L a/c is about the same efficiency as the liquid cooleds of the same
vintage. This would be fun to evaluate.

What do you think?

Kim Howe
khowe@omninet.net.au