At 12:27 PM 2/3/99 -0500, Art wrote:
>I can't see why an engine would run any hotter with straight propylene
>glycol than it would with a "normal" coolant provided you use an
>appropriate thermostat. The advantage you would have is that when it
>did get a little hotter than normal it wouldn't boil over, it would keep
>on going and do a better job of cooling than a boiling liquid with it's
>vapor pockets at the hot spots which need the most cooling.
Okay, I'm no chemist, but be a little careful here. Just because one
coolant boils at a higher temp than another does doesn't mean (to me) that
it'll cool an engine better. You have to take into account the specific
heat of the agent (the 'ease' (for lack of a better word) with which the
coolant will take up heat (in the engine) and give it off again (in the
radiator)). If it returns to the engine from the radiator not much cooler
than it was when it left the engine, this isn't good. Its my understanding
that straight ethylene glycol is inferior to a 50:50 mix with water in this
regard. The glycol/water mix is better at heat transfer than is straight
glycol, if also able to boil at a lower temp. Of course, Art is correct to
say that a vapor pocket also seriously hinders heat transfer (minimally by
blocking the flow/contact area of liquid coolant). The whole thing is to
strike a balance/compromise between a given coolant's boiling point, its
specific heat, and its freezing point (given a specific thermostat/radiator
combo).
I'd echo the remarks made by another list member with regard to NASCAR
coolant formulations, race vrs. street engines, oil changes and rebuilds...
IMHO, the straight ahead approach is a 50:50 glycol/water mix, a 160-180F
thermostat, correct timing/fuel mix, and a re-cored radiator for any street
car that tends to run 'hot.' Maybe an oil cooler...
In the final analysis, I'm reminded of the remarks a jag mechanic made to
me when I asked him if my old E-type (please, I wish I NEVER sold that
car... except that it financed me Mog) was running too hot
Me: "Is this car running too hot? It cruises at an indicated 190-200F!"
Him: "Has it boiled over?"
Me: "Nope"
Him: "Then its not running too hot."
my two cents worth, anyway...
cheers,
WZ
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