Glycol or Water; which is the better Coolant?

[Fixer]

Reading after work and thought i'd share this info since Summer is around the corner. I always heard straight water cooled best but here are the numbers:

The specific heat capacity is less than that of pure water in a 50% solution, ethylene glycol's specific heat capacity when compared with pure water is decreased by 17% at 200 F. Propylene glycol has an even lower specific heat.
at 100-gpm coolant flow rate and an energy loss through the coolant system of 189.5hp,

The water temperature increase would be 10 degrees,
Ethylene glycol water mix would gain 20 degrees,
Propylene glycol would gain 33.3 degrees F.

Our aluminum 928 motors and radiators are to only use Ethylene glycol in them as coolant/water mix.

To compensate for these mixes more coolant would need to be moved thru the system.

Running 100% water is the most efficient coolant in terms of its ability to conduct heat with minimal temperature rise. IOW, of all common liquids, water requires the most heat energy to change its temperture.

Vapor point is raised slightly by ethylene g. and propylene.g. coolants though and can therefore absorb heat at higher temps w/o boiling.

But even with its lower vapor point water still carries more heat per unit.

You can raise the waters effective vapor point by using a higher pressure radiator res cap. For every pound of increased system pressure, water's boiling pt goes up 3 degrees. Our quality aluminum radiators allow us to operate at higher system pressures when compared to brass/copper radiators. Aluminums tensile strength is greater than brass as you all know.

To end this,

an aluminum radiator filled with pure water and using at least a 20 psi cap is by far the best heat transfer set up provided it is not subject to freezing.


Hope you found this interesting.

[Fixer]

Thank you Stan, i have never heard running mostly pure H2O with c.i. could cause head gasket failure.
Will look into this.
Not trying to re write any book though Stan, I said i was sharing the info regarding Heat Transfer of Water Vs. E.G.
I am using Zerex now, and I just drained the system a month ago and refilled with 50% solution.
I drain my coolant every year in all my vehicles and have never experienced any mechanical failures due to my driving and maintenance habits.
Glad you're out there.

[Fixer]

Thanks again Stan, will do.
How do you feel about 60% distilled and 40% Zerex plus wetter for Summer?
what wetter do you use?
Good advice and makes sense.

[Danglerb]

Carl at 928 motorsports is trying some things related to cooling, bumping up the system pressure etc., but unless you want an adventure stick to what Stan says. Zerex G05 is good for more than a year, maybe as much as 5 years.

[Fixer]

Again, I wanted to share the data in this tech forum running 50/50 Zerex now. Summer will be diluted a little. I don't mind draining i enjoy it.
Thanks.

[Fixer]

Working on the car I ended up draining 2 gallons of 50/50 mixed coolant from my 928 and topped of with only distilled water, still when examining the coolant this am while changing hose clamps the diluted coolant is plenty full of coolant and slick to touch. Can't get rid of the slime.
The car runs very nice and cool, been checking a lot. Added Redline Wetter which contains corrosion inhibitor also.
No worries, no regrets.

[Danglerb]

The issue with lower coolant percentages isn't overall system temperature, its the peak temperature in the motor, usually the heads around the exhaust ports where boiling creates a steam pocket and runaway temperature rises in the head leading to cracked or warped heads.

I have about a 3/4 inch gap between the outside of my fan and the factory shroud, which I needed to seal due to the level of reverse air flow.