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and I disagree that pure water cools better than a mix. That's why pure water boils earlier than saltwater, etc. Coolant formulas are what they are for a lot of reasons, and keeping the system under pressure also raises the boiling point.
The boiling points are different but once we hit those in a pressured system we're way into the danger zone in an SBF. The extra 15 degrees offered by the coolant (at 265F) doesn't really buy you anything. The boiling point of the cooling medium is not an effective measure of thermal transfer. The heat transfer property of water is better than glycol coolants by a factor of over 2 times. That's where some of the "water is better than coolant" argument comes from. While that's true as a point of physics in this application coolant may work better than pure water. (doesn't necessarily have to be a glycol coolant) We're talking about heat transfer in a specific application and not as a general principle of the medium. Engines are cooled by convection and it's a complex process with many variables. The properties of whatever cooling medium are only one of the factors. In this app the surface tension of the water during higher duty cycles is one reason it loses its effectiveness compared to cooling additives. Turbulence in the flow could be another.

In terms of practical purposes street cars should be running glycol based anti-freeze. First off many places in the US freeze and water alone or non glycol additives don't offer any protection from freezing. It's readily available, it works and in late model cars the cooling systems are designed to use it. In the Focus I use 50/50 per Ford. In the Mustang I use water and Water Wetter. Even at 110* during the summer with a stock cooling system I'm well within the operating window of a stock 289 doing 70-80 on the freeway.
 

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The boiling points are different but once we hit those in a pressured system we're way into the danger zone in an SBF. The extra 15 degrees offered by the coolant (at 265F) doesn't really buy you anything. The boiling point of the cooling medium is not an effective measure of thermal transfer. The heat transfer property of water is better than glycol coolants by a factor of over 2 times. That's where some of the "water is better than coolant" argument comes from. While that's true as a point of physics in this application coolant may work better than pure water. (doesn't necessarily have to be a glycol coolant) We're talking about heat transfer in a specific application and not as a general principle of the medium. Engines are cooled by convection and it's a complex process with many variables. The properties of whatever cooling medium are only one of the factors. In this app the surface tension of the water during higher duty cycles is one reason it loses its effectiveness compared to cooling additives. Turbulence in the flow could be another.

In terms of practical purposes street cars should be running glycol based anti-freeze. First off many places in the US freeze and water alone or non glycol additives don't offer any protection from freezing. It's readily available, it works and in late model cars the cooling systems are designed to use it. In the Focus I use 50/50 per Ford. In the Mustang I use water and Water Wetter. Even at 110* during the summer with a stock cooling system I'm well within the operating window of a stock 289 doing 70-80 on the freeway.

I used water wetter in my FJ40 and it’s really good stuff
 

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I hope that’s not what I wrote. If so it’s a typo. I’d never run 100% water unless an emergency. I was saying I’d ruon the 50/50 mix and wouldn’t waste my time going higher mix of antifreeze or straight antifreeze. Running straight water will have a lower boiling point and is corrosive and will shorten the life of your engine
If one adds a bottle of water wetter to pure diltilled and deoinized water, then then is more than enough lubrication for the water pump and the water wetter has the anti-corrosive properties also. Of course there is no Freeze protection if that is needed. I recently put a bottle of water wetter in my daily driver, an '02 Jaguar XKR, and removed enough 50/50 coolant to lower the antifreeze % to 33%. My peak temperature dropped 6 degrees immediately. I'm now going to take out enough coolant and replace it with enough pure H2O to lower the antifreeze % down to 25%. probably will leave it there. Water has a much better heat transfer ability than 50/50 antifreeze mix. The less antifreeze you can get by with, the better, IMHO. Of course you need to have something like water wetter in the system for lubrication and anticorrosive properties.

Z
 
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