I don't buy the claim that the high boiling point eliminates hot spots. It takes a comparatively large quantity of heat energy to boil water (or any fluid.) What that means is that it's very difficult to develop hot spots above the boiling point of the coolant. If a localized spot goes above the boiling point then it will cause some coolant to boil. Just enough coolant will boil to bring the temp of the hotspot down to below the boiling point. The 'steam' that results moves along with the rest of the coolant and eventually recondenses releasing the heat energy that it picked up at the hotspot.

To repeat: hotspots are unlikely above the boiling point of the coolant. If the boiling point is 350F, then hotspots as high as 350F are possible. If you use a coolant with a boiling point of 230F (at 15 PSI or whatever your cap blows at) then hotspots above 230F will be unlikely.

This is freshman physics.

 

Ever watch a pot of water boil? You see how it forms air bubble on the bottom before it actually starts boiling and before a temp prob suspended in the water reads 100*C? Thats more or less what we're talking about, those air bubbles sitting on the surface are the devil.

 

Exactly! Those little air bubbles are the consequence of hot spots that reach a temp above the boiling point before the rest of the bottom of the pan. A little bubble forms 'using up' the heat at that spot and keeping it just below the boiling point. If the bubbles didn't form and remove localized heat then those spots would become hotter.

Ideally, the cooling system in an engine stays below the boiling point. But if localized hot spots do appear then bubbles form cooling the spot and carrying away the heat. The point is that the hot spots are able to get only as high as the boiling point before the Cooling Bubbles form.

Raising the boiling temp of the coolant doesn't help prevent hot spots, it hurts. Raising it from 100C to 200C hurts a lot!

Not sure what you mean by "the devil."

 

I've heard of many stories like this with Evans, and saying that raising the boiling temp of the coolant hurts seems to fly in the face of what some seriously respected posters on this forum say (I.e., going to a higher psi cap).

 

Lol @ cooling bubbles. Right, the air carriers away more heat than the liquid eh?

The bubbles are a sign that the liquid in that area has gotten so hot it has undergone a phase change. Though that phase change is absorbing some of that heat energy, after the bubble is created that spot is no longer being cooled.

At least that's my understanding. While a hot spot caused the bubble, it certainly doesn't seem to me that these are in any way "cooling bubbles." They are getting in the way of more liquid coming to carry away the heat. No bubbles = constant liquid contact with the hot surfaces = less extreme hot spots.

 

I don't see the bubbles staying where they are if there's coolant flowing.

But, I suppose cavitation could be reduced. I'll go along with that.

 

One real test is to see if a detonation-advance-limited motor can run more advance on the dyno.

But alas only one magazine has done a test like that.

 

GoLytely FTL.

 

Yes, those bubbles are the devil. They reduce the amount of heat transfer between the engine and the radiator and allow the metal under the surface of the bubble to go about the boiling point of the coolant.

 

A buddy of mine used the Evans and it was thicker than water and seemed to get thicker over time, which I found scary. It seemed like a lot of extra drag on the water pump and subsequent horsepower loss.

 

I don't get why we are so hung up on the formation of a bubble due to a hotspot.
Water in the kettle is stationary, coolant in a system has a pump motivating it all over the place. That particular hotspot will never cause a phase change on a group of water molecules, because they will never hang in one spot long enough to establish a meaningful relationship with a heat source.

 

Evans is blood?

 

The power stroke happens in it's entirety in 15ms at 4000 rpm. Detonation happens in a fraction of the time it takes to complete a power stroke. The coolant in the cooling passages around the combustion chamber is moving at maybe 1-2m/s. The wall between the combustion chamber and the cooling passages is ~3mm thick aluminum. If microboiling happens, the bubble will absolutely hang on long enough to cause an effect in the combustion chamber.

The question isn't, "Will bubbles in the coolant hang on long enough to have an effect?" The question is, "Does micro boiling happen (probably), and do the bubbles matter?" And the only way I know of to find out is empirical testing, which NASCAR has been courteous enough to conduct for us, and they seem to think this stuff is worth any compromises it comes with.

It's not that expensive in the scheme of things, and it seems to work. I don't see any reason not to do it.

 

I do get your point.

I still do not think a single combustion event will cause a microboil spot. It would take a series of those events - with exhaust and intake cycles in between - and enough new coolant would have moved into that particular spot by then.

On a different but related note, I have seen a max of about 94C in coolant temps on the 5.3 Km F1 track on a July day. Max oil temp was 105C. I think a proper reroute, a double row 55 mm radiator, a functioning undertray and radiator ducting have a far more positive effect on cooling than trying to optimize heat transfer within the engine.

Just my two cents.

 

But those are Turkish cents. What's exchange rate?

 

Cents are cents. Really.
I mean, I did not say "Just my two one hundredths of some country's monetary currency".
Around here, it would be kurus (kurush or kuruş).

In any rate, had I offered my opinion in Turkish currency, it would add up to about one cent. Currently two of our "Lira"s buy one $.

 

source

I think I'll stick with water & water wetter.

 

Looks like evans isnt propylene glycol, or at least not entirely. The MSDS lists greater than 60% as ethylene glycol. It does have propylene glycol in it.

 

Skimmed through it and it seems like some good info toward this debate. http://www.norosion.com/evanstest.htm

 

But you have to doubt the validity of all the data due to testing bias.