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Question for Cooling Engineers

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Jeff

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Question for Cooling Engineers
« on: July 24, 2006, 09:34:17 am »
Let's talk cooling...

I run honda's, and since the 600rr came out, it has been a HOT running bike.  Not sure why, but the Honda always runs hotter than the other bikes out there.  Anyway, onto the question/discussion...

My bike, running my (legal) coolant, will get upwards of 240 on the track if the temps are REAL high (like last BHF).  When I pull off, it can spike as high as 250.

The SAME bike running water & water wetter is running a solid 10-13 degrees cooler, in the high 220's, low 230's.

Here's the question...

My coolant has a boiling point of 370 deg F.
Water is 212 deg F.

In order for water to have a higher boiling point, it needs increased pressure.

The increased pressure of the water reduces the water pump efficiency, and can, in effect actually stop flow if it gets high enough.  I don't know though at what point this occurs in this particular bike.

The coolant I run has virtually NO pressure at 250 degrees, so the flow is perfect.

At BHF, the 05 CBR600RR with the water in it (same motor build, etc) came off the track and blew 2 hoses off the radiator (evidence of ALL hoses pushing out and moving) because the pressure was so damned high.

My question is to those who KNOW cooling.  Not to those who "think" or have been told.

Is it better to have the higher pressure yet with 10-13 degrees cooler operation OR better to have no pressure and perfect flow with 10-13 degrees more heat?
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Super Dave

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Re: Question for Cooling Engineers
« Reply #1 on: July 24, 2006, 11:57:08 am »
Well, yeah, good question.

As water gets hot in the engine, you'll get the air bubbles at the point of hot spots...just think of boiling water for macaroni and cheese.

When that happens, you're kind of screwed because the heat of the engine now is not in contact with the liquid coolant...it's trying to push off heat through those little air bubbles.

Watter wetter products reduce the surface tension of the water which causes the size of the little bubbles to be smaller.  If you can get the heat into your coolant, then one can carry it someplace else (radiator). 

When you get all the bubbles, the heat isn't transfering to the coolant.  The engine temperature will increase.  Remember the temperature that the bike reads is the temperature of the coolant, not the temperature of the physical engine.

The pg coolants don't boil until some ridiculous number...so they continue to take in heat and move it to the radiator. 

I think that the higher registered temperatures come from their ability to continue to take heat from the metal that water does not.

That make sense?
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Thingy

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Re: Question for Cooling Engineers
« Reply #2 on: July 24, 2006, 12:11:26 pm »
That is a good question Jeff.  Do you know if Water Wetter raises the boiling point of water?  I suppose I could go look at a bottle in the garage...
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Super Dave

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Re: Question for Cooling Engineers
« Reply #3 on: July 24, 2006, 12:17:09 pm »
Don't believe that it does.  It has serfactins to reduce surface tension.  I get the same affect by adding Palmolive to watter if that's what I want to use.

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Jeff

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Re: Question for Cooling Engineers
« Reply #4 on: July 24, 2006, 12:27:15 pm »
I think that the higher registered temperatures come from their ability to continue to take heat from the metal that water does not.

That was my thought exactly...  Water is boiling.  PG has less surface tension and cavetation (I believe that is the term), so it is actually cooling better.  However, why the hell is the temp registering higher with PG vice water???

My only thought is that steam can only get so hot, so the temp gauge with water is giving somewhat of a false reading.
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Super Dave

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Re: Question for Cooling Engineers
« Reply #5 on: July 24, 2006, 12:40:11 pm »
That was my thought exactly...  Water is boiling.  PG has less surface tension and cavetation (I believe that is the term), so it is actually cooling better.  However, why the hell is the temp registering higher with PG vice water???

My only thought is that steam can only get so hot, so the temp gauge with water is giving somewhat of a false reading.

I don't think it's a false reading.  Water just can't absorb all the heat.  So, the coolant is only X degrees.  PG absorbs more heat so, that coolant is hotter.  It can take the heat someplace else then, where water can't move the heat because it cannot absorb it when it starts to boil.
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Jeff

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Re: Question for Cooling Engineers
« Reply #6 on: July 24, 2006, 01:36:49 pm »
So which one is hotter?

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Re: Question for Cooling Engineers
« Reply #7 on: July 24, 2006, 01:37:06 pm »
The answer to you question is simple.  Water has a greater thermal efficiency than coolant (ethylene or propylene glycol) mixed with water.  Every liquid known to man has a fixed ability to absorb and release heat (BTUs).Distilled water just so happens to be better at this process than water and coolant.  What water does not do better than coolant is prevent corrosion and lubricate the water pump seal.  Dave is correct about the water wetter.  Here is why: Water wetter (which is essentially soap) increases the surface tension of the water, this in turn keeps better contact between the water and the hot component you are trying to cool.   The more surface area that you have in contact with the coolant, the greater the transfer of heat to the coolant.

I am not cooling engineer...
But I did stay at a Holiday inn
 
Guy
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Jeff

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Re: Question for Cooling Engineers
« Reply #8 on: July 24, 2006, 01:37:57 pm »
Bill, water wetter doesn't increase boiling point.  Only reduces surface tension. (and lubricates the pump, etc)
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Re: Question for Cooling Engineers
« Reply #9 on: July 24, 2006, 01:40:21 pm »
Guy, I can understand that and agree with it up until the point of boiling, and/or the point where the pressure in the system is so great that the fluid movement is hindered.  (man I hate overanalyzing things)
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Re: Question for Cooling Engineers
« Reply #10 on: July 24, 2006, 06:17:10 pm »
If you have heat under control, I think water works really well.

In some applications, PG can help keep a cooling system cooling. 

NASCAR made PG illegal because teams then found that they could continue to remove heat from thier engines without inlets in the front body for the radiator.  That gave them an aerodynamic advantage

I use no water in my bus cooling system.  It's a PG/EG mix.

I'll agree with Guy that there are differences in how things other than water dissapate heat.

The flip side is that we're dealing with production items.  Every CBR600RR I've ridden has been "hot".  Internally, there is probably some kind of flaw in the engineering of the coolant jacket.  Ultimately, it's probably all air at that spot as water is unable to do anything there. 
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loc_dogg

Re: Question for Cooling Engineers
« Reply #11 on: July 24, 2006, 09:03:18 pm »
honda s are actually engineered to run hot for emisions/ efficiancy purposes. I have also read and studied alot about the same prob. I run kool aid in my 05 and it gets up to about 230-240. any more than 250 and you may cuase damage. the thermostat does not even open till 183. you may be able to remove it but it may run to cool aswell. you can also research that. yes, i do race my bike.(ccssw)
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