Dave, et Listers,
I still stick by my previous story on this subject. One question you can
ask yourself is what do most auto manufacturers put in their new cars? Most
of these car manufacturers are not like Brad Parlee, "just looking for a
way to spend more money" when they fill their radiators. In fact, these
guys wouldn't part with a nickel they don't have to. If distilled water,
even with additives, actually worked as well as water/glycol mixtures I'm
pretty sure that's exactly what they would be using. BTW, does anyone
happen to know the prescribed mixture for any standard production car? From
what I've seen, they must use at least a 50% glycol. Now certainly factors
included in the choice of coolant includes corrosion and, yes, maybe they
want to be able to sell you coolant at $5 a gallon instead of letting you
just fill it up with water. But the manufacturers have performance
standards that have to be met, and using a less efficient coolant would
mean having to compensate with a larger (more expensive of course)
radiator. Not a smart economic tradeoff I think. For most racers, the use
of glycol coolant is prohibited and straight water works quite well enough.
They usually use additives like water wetter and higher pressure caps to
help compensate. Besides, if your engine gets over 245 degrees, it's
probably time to pull over before you do some real damage anyway.
Incidentally, I believe if memory serves me, that it is the heat capacity
of water that is 2.4 times that of glycol, not the thermal conductivity. In
any case, the thermal conductivity is a very minor parameter, much less so
than the heat capacity.
Taking a sharp detour to another remotely related subject, I ran across an
empirical formula for calculating horsepower based on quarter mile speed in
a car magazine recently and thought, if you haven't seen it, you might find
it useful. Here it is:
h.p. = (q.m.speed/234)^3 * weight
For example, if your car does 105 mph in the quarter mile and weighs 2600
lbs, then:
h.p. = (105/234)^3 * 2600 = 235 horsepower
They didn't say, but I assume from the answer that they mean net horsepower
at the rear wheels. So, save yourself the trouble and expense of a chassis
dyno and go run a quarter mile and not only get the answer, but have more
fun to boot!!
Bye for now,
Bob
At 07:24 AM 9/24/98 -0700, Dave Binkley wrote:
>Saw the following in the May 98 issue of Car Craft and have been meaning to
>post it. The recent postings reminded me to go dig the mag out and send
>this along. The article was entitled the "25 Lies Car Magazines Have Told
>For Years".
>
>"Lie Number 9: Glycol-based antifreeze is the best engine coolant. The
>Truth: Plain water is the best coolant. Water has 2.4 times greater thermal
>conductivity than conventional ethylene-glycol-based coolants. Glycol is
>also much more viscous than water, and the more viscous the medium, the less
>the heat transfer rate. Glycol has a higher boiling point than water, but
>even when using a 50/50 water/glycol mixture with a 15-psi radiator cap,
>glycol's boiling point is only 15 degrees more than plain water. If you
>have a marginal cooling street car, try reducing the amount of glycol
>antifreeze in the system and increasing the water content. A 33 percent
>glycol/water mix won't freeze until 0 degrees F. On a race car or street
>car not subjected to freezing temperatures, consider running only water as a
>coolant."
>
>They go on to mention how ordinary tap water is extremely corrosive and try
>to use distilled water.
>
>Dave
Robert L. Palmer
Dept. of AMES, Univ. of Calif., San Diego
rpalmer@ames.ucsd.edu
rpalmer@cts.com
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