Presently I am running straight water in my engine with a corrosion inhibitor.

I know water has the best ability to pull heat....BUT, will adding coolant stop detonation better?

Water will tend to boil sooner correct?

Say you have a hot spot on the cylinder wall, water will boil there before water/coolant causing a detonation situation correct?


David

 

the boiling point goes up under pressure. But its an interesting if the coolant does any better. I would like to know as well


I sure don't want AF leaking going down the track vs. water.....

 

Just use deuterium and you won't have to worry about it.

 

Water conducts heat better than an antifreeze mix however it also rusts. Using an additive such as WaterWetter changes the surface tension of water and will add a rust inhibitor.

Boiling point increases as pressure increases. No pressure and water or an antifreeze mix will both boil at 212F. Using a 15 pound rad cap, the boiling point is increased to something like 230F.

Some people think you should cycle the cooling system as fast as possible but that's wrong. A water pump turning too fast and/or running without a thermostat moves the coolant through the engine too fast for it to pick up heat causing hot spots. Too slow and the whole engine overheats. Running without a thermostat usually needs a flow restriction in place of the thermostat to slow the flow down.

The thermostat maintains a minimum temperature. If the coolant temperature drops below the thermostats opening temperature, it will close allowing the engine to build more heat. Once the engine goes past the thermostats opening temperature, the thermostat will stay open even if the engine runs too hot and overheats.

The radiator's job is to remove all the excess heat from the engine providing the water pump can circulate the coolant through the system at a speed slow enough to allow the coolant to absorb the engine's heat.

 

Water boiling point:
-atmospheric at sea level, 14.7psia = 212*F
-at 20psia (5psi increase) = 228*F
-at 30psia (10psi increase) = 240*F
-at 35psia (15psi increase) = 250*F
-at 40psia (20psi increase) = 260*F

The boiling point of ethylene glycol (common coolant) is not the same as water, and the boiling point of water/ethylene glycol mixtures increases with the percentage of ethylene glycol in the mixture:

-10% EG = 214*F
-20% EG = 216*F
-30% EG = 220*F
-50% EG = 225*F
-100% EG = 387*F

By adding ethylene glycol to water, the combined material has a higher boiling point vs. radiator pressure than water alone.

If I understand this, you are saying that with no t'stat, an engine will overheat, because the coolant is moving too fast to cool it.

This reverses the laws of thermodynamics. Increased velocity increases turbulance. Increased turbulance increases the heat tranfer coefficient. Increased turbulance helps remove steam bubbles from the surface of the exchanger, limiting hot spots and improving overall heat transfer.

Increased velocity results in increased mass flow. Increased mass flow means the coolant has to heat up fewer degrees to remove the same amount of heat (BTU's). The lower the temperature of the coolant, the larger the driving force between the hot side and the cold side of the exchanger (log mean temperature difference), and the higher the heat transfer rate.

The flow restriction (added when there is no t'stat) is there it prevent the circulating coolant from over-cooling the engine, reducing its thermal efficiency and power production.

 

What I meant was, if you have a hot spot on the cylinder wall...which is what causes detonation. Water will boil causing an air bubble AT the hot spot on the cylinder wall correct? Will adding coolant help this situation?

I know coolant system pressure raises the boiling point OVERALL, but what about at the SITE where the hot spot is on the cylinder wall...or wherever it may be?

David

 

I wanted to say this, but didn't want to spark the controversy and argument that always ensues.

 

Increasing pressure raises the boiling point of the coolant in the entire system. Whether it's next to the combustion chamber or in the radiator, etc doesn't matter. Adding coolant has the same effect.

 

I didn't want to quote the whole thing.

Yes and no. Increased velocity will eventually cool it down however if the coolant is flowing too fast, it doesn't stay in the engine long enough to absorb heat and doesn't move through the rad slow enough to remove the heat. You'll be feeding too hot a coolant back into the engine trying to remove more heat.

If you had a big *** aftermarket rad capable of removing huge amounts of heat quickly then the increased coolant flow wouldn't be so bad.

Adding a restriction such as a thermostat will slow the flow down and allow it to pass through the rad slower to remove the excess heat. The opening through a thermostat is considerably smaller than running without a thermostat.

 

Its kinda like this, when you test an A/C system it ALWAYS blows colder temps with the blower on low speed, why? The air spends more time on the evaporator getting colder. The air TEMP is colder.


David

 

As Injuneer implied, all heat transfer theory states that higher fluid velocity equates to higher heat transfer rates. Coolant can't flow "too fast" to "pick up heat" or "lose heat". In a closed loop, no matter how fast it moves, each unit of fluid is spending the same amount of time in any given place. The way to increase heat transfer, without changing material properties, is to increase flowrate.

An AC system, on the other hand, is not a closed loop, and is a completely different scenario.

 

A/C Is closed loop with the settings on MAX.

It is the same concept, the slower the air is moving the more it is cooled, same a coolant in a rad, the slower it moves(to a point) the more it gets cooled.

David

 

Let's look at this carefully......

Per your theory, if the coolant is moving too fast, the engine will not cool down.

So... you add a restriction to slow the coolant down, and the engine cools down.

But if you make the restriction too small, the coolant will slow down too much, and the engine will heat back up.... that's what the thermostat does is it pinches down the flow.

Using this approach, there is the perfect size restriction that will provide the exact coolant flow that will produce the maximum heat removal from the engine.

Is that what you are saying?

If so, what engine operating condition do you size this optimum restriction for? If you sized if for idle or low RPM, when you went to high RPM, the coolant would again be moving too fast, and the engine would start to overheat. If you sized the optimum restriction for high RPM/max coolant flow, when the engine was idling the coolant velocity would be very low, and there would not be adequate cooling.

Sort of doesn't make a lot of sense.

 

I know what you're trying to say, but it's wrong. Faster flowrate = more efficient heat transfer.
The fact that the air coming out is warmer doesn't mean that heat transfer has dropped. Maybe heat per unit volume. Unless you can measure mass or volume airflow with your hand as well as temperature, sticking your hand in front of the vent doesn't mean a thing.

Try this - cut the power to the fan cooling the heatsink on your computer's CPU. Give that air a whole lot of time to dwell in there and soak up heat. If your theory is correct, it should run nice and cool...

 

So that means the air represents the coolant, and the evaporator is the engine walls. To get the most out of the metal, you turn the flow to max.

Your a/c air feels colder on low, but it's the temp of the metal you're concerned about. It's not releasing it's temps as fast as it could be if there were more flow over the surface.