Kim Howe wrote:

> 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.

Hmmmm....IMHO this is only accurate *if* each engine is run under
optimal conditions. A hypothetical example:

Let's say that both engine A and B operate at 70% efficiency
(taking into account combustion efficiency, frictional losses,
etc.), while operating at 5000 RPM, and 80% efficiency at 3500 RPM.
The frictional losses, and concomitant frictional wear, would be
much greater operating at 5000 RPM *with* a lower efficiency. Thus,
engine A operating at 5000 RPM would be expected to produce, over
its lifespan, significantly less 'work' than engine B running at
3000 RPM.

> 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 why do you think the radiator has drag? Think of the radiator
as a perforated plate. Which has more aerodynamic drag, a 15 ft2
solid plate, or a 15 ft2 perforated plate?

>... 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).

I've not seen the calculations you reference, but I fail to see how
they could be accurate. A direct air cooled motor needs a large fan
to move tons of air. This requires significant horsepower. On the
water cooled side, you need only calculate the hydraulic losses
(and minor pump frictional losses) and compare to the fan (were
talking modern systems with electric radiator fans). While the
hydraulic requirements *may* be higher, I would tend to doubt it.
As stated above, the radiator (unless its incorporation directly
results in a greater aerodynamic cross-sectional area) does not add
drag.

> 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

Well, thermodynamic calculations aside, it requires only direct
comparison of the 2.0l a/c with the 1.9L or 2.1L wbx, relative to
fuel economy (in the same weight/configuration vehicle), to
determine net efficiency ratios. With the 2.0l a/c getting 25%-35%
lower mileage than the 2.1L wbx (under the same conditions, in
every instance I've seen - including my own vehicles), the wbx is
more efficient. What am I missing here?

Keith Hughes