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?
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?
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...
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.
Quote from: Super Dave on July 24, 2006, 11:57:08 AM
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.
Quote from: Jeff on July 24, 2006, 12:27:15 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.
So which one is hotter?
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
Bill, water wetter doesn't increase boiling point. Only reduces surface tension. (and lubricates the pump, etc)
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)
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.
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)
removing a thermostat is a BAD idea.
If you're gonna do that, just gut the thermostat or buy/build a restrictor plate. You want the flow restricted or there will be no heat difference in the coolant.
Likewise, I don't think it's necessarily a problem in the honda, it's just the way it was engineered. There is no real ill effect from it on a whole model basis.
Interesting question.... & :banghead:
In my past expericence both must be considered, but (just to over add to the overanalyzing) you also have to factor in the effect it is having on combustion chamber tempature. This then trickles down to chamber shape & design, actual composition of the alloy used to cast the head (thermal coefficient), piston crown design, piston tempature differential, etc.....
Some engines are designed to run "hotter" and may actually have more efficient combustion at a coolant temp of around say 230ish, than if they are run at a lower temp, say 180ish.
I suspect that the CBR600RR's run hotter than average becuase they were designed to. But without actually knowing the effect the coolant temp is having on combustion there is no way to be sure.
So.... for a short anwers, I have no idea which is better, without knowing & analyzing the rest of the variables.
Hey..... quit analyzing your cooling system and write up the lastest BHF race report.
Quote from: Jason748 on July 25, 2006, 12:30:11 AM
Hey..... quit analyzing your cooling system and write up the lastest BHF race report.
I've actually got it written, I just need to sort out a few pics and get it up online. Should be able to complete it tonight.
Jeff,
Please explain your theory on how increased pressure stops coolant flow.
Guy
Guy, I looked for data to support the theory I had in my head, but ran out of time before I could find any. I don't know this to be certain, hence my request for those "in the know" to reply.
I do not think pressure effects the coolant flow. The entire cooling system is under the same pressure (give or take a little, I'll explane later). Because the radiator cap is essentialy the pressure control mechanism for the cooling system, both the inflow and the outflow sides of the water pump have that pressure exserted on them because they are connected directly or indirectly connected to the radiator. There is a small differential pressure generated by the water pump to move the coolant. On the outflow side of the pump the pressure would be the cooling system pressure + the pressure generated by the pump. On the inflow side of the pump the pressure would be the cooling system pressure - the pressure generated by the pump.
So when you stated that you use coolant without pressure, how are you accomplishing this? Are you removing the spring on the radiator cap?
Guy
The pressure created in a water system is caused by 2 factors.
1. Expansion
2. (the big one) boiling point
Remove the boiling point (or raise it dramatically) and you have only to contend with expansion. PG coolant expands roughly 15% at 250 degrees F which creates like 4 point some-odd PSI. Water, however, is at a much higher pressure due to it boiling within the cooling jacket of the cylinder.
Jeff,
here is something I found on the internet referring to boiling point. I am sure you know this but I though it was interesting trivia
water boils at 212 F at atmospheric pressure, at sea level. If we put the water in a sealed container and increase air pressure to 15 psi above atmospheric pressure, we can raise the boiling point to about 250F. Then, if we trade the plain water for a mixture of half water and half ethylene glycol and put it in the same container with 15 psi of air pressure, we raise the boiling point even higher-to about 265F.
Here is what I found out about Propylene Glycol
Boiling Point (sea level):
219° F at 40 percent concentration
222° F at 50 percent
225° F at 60 percent
increase by 40° to 45° F if a 15 psi radiator cap is used
So if we assume the above to be true, your bike should not be boiling at the temperatures you reported. Which indicates to me that if you were to run a 60/40 mixture of distilled water and propylene glycol and your cooling system pressure is correct, you should not boil over.
In order to blow a properly installed radiator hose of it would seem that your cooling system pressure would need to be higher than the 15 to 20psi that your cooling system should be under.
These things make me wonder what might elevate your cooling system pressure above normal.
Two things come to mind.
1) Your radiator cap is malfunctioning allowing excessive pressure to build up until the hoses blow off.
2) You have combustion pressure gasses getting into your cooling system causing abnormally high cooling system pressure.
Guy, you misunderstood my first post. I'm talking about 2 separate bikes.
First the bike with the water & water/wetter in it... This was the first weekend out with this bike. It is our belief that the hoses were not properly clamped. Additionally, it popped the hoses after stopped in the pits, when the heat raises to the highest point.
Second, the bike with the NPG. It's mine and I've been running it all year with this motor build. It is running 100% NPG coolant. There is no water or EG in the system at all. NPG boiling point is 369 deg F at 0 PSI.
After having this discussion here and other places as well as with several thermo-dynamic engineers, I am not really as concerned as I initially was... The PG coolant is recording hotter at the temp probe because it is still absorbing heat from the motor, whereas the water may very likely be maxed out on its heat transfer ability.
Jeff,
I'm not an engineer but as I see it your concern is the engine temp not the coolant temp. If you really want the answer then you can get rather inexpensive cylinder head temp sensors that mount under the sparkplug. If you were to fit one of these then you could compare the actual engine temp to the temp reported by your coolant temp probe. This would then tell you if the NPG is not transfering heat effectively to the radiator or the water is not picking up heat from the engine.
Just my .02
This is not related to your original question here, Jeff, but I think that Guy may be onto something here. When I have had bikes overheat before, the fluid came out of the radiator overflow hose way before it would pop off any of the coolant hoses. Maybe the radiator cap is not working properly, or like you mentioned, the hoses were WAAAAY loose. I kind of doubt that all of the hoses would be loose though. Whoever the owner is may want to have the radiator cap of that other bike checked.
Edgar, we'll check the cap as well, but the bike was JUST put back together like the day before the hose blew off. We should have gone through the bike beforehand but just didn't... But in any event, we're looking at it.
thanks guys.
Jeff, I think you're looking for a better remedy instead of a cure. I ran the same bike, with a 122HP motor that I did mostly myself and never ran over 210, even on a hundred degree day at RRR. I'm sure you know there's a hundred different things that could be causing your dilemma, but if you've been over the cooling system well (and it seems you really have) then you might need to start looking elsewhere.
The combustion chamber is where I'd start, more directly, the fuel. Are you running stoiciometric, lean, rich... what plugs?, what gas, etc. It may end up the cooling system is doing it's job but you're overloading it. You may even have a slight detonation problem that you're not hearing... have you milled anything?
I ran sans thermostat with a restrictor plate, I really recommend that for starters. It seems that the flow rate given by a 1/3 reduction in the hole size moves the most water while still allowing it to pick up the heat.
If you've got a few hours you should pop off the head and snoop around... you can learn a lot from doing that. While you're in there check for corrosion in the cooling system channels. I'm sure you use distilled water, but maybe someone else didn't ??
Just thinking out loud.
No water in the system now or ever.
Head is milled down
Fuel is VP U4
I haven't been completely through the cooling system, I'm sure that I can gain some cooling by cleaning the crap out of my radiator as I haven't done that in quite a while.
I actually have a new super-secret device on the way from Europe which was designed for the bike for this exact issue. (okay, so it's not that secret, it's some fancy oil cooler which is bringing temps down 5-10 deg).
More to come, certainly...
Curious to see how it all goes... +1 on the cleaning thing. When I rebuilt the R1 motor I decided to sit down and individually straighten each fin in the radiator and clean it... there was a half pound of debris in it!!!
Off topic, but why is propelene glycol legal anyway? I realize that it would be easier to clean up after a spill, but it's still slippery as hell.
it's legal because it can be cleaned up easily. The bad piece to it is that it HAS to be cleaned up (unlike water)...
Water = no cleanup (generally)
PG = mandatory cleanup but easy to do
EG = difficult and mandatory cleanup
Im running two 05 600RR this year, and had issues with temp. There are some things to do but I can't tell you all I can say is pay attention to the factory bikes.
I know the secret of life too, but I can't tell you. All I can say is pay attention to midgets. :wtf:
Why Greg? All they look up to are asses!
Well Jeff,
Did your cooling systems fair any better Saturday at Gman? Seemed lik a pretty good test day.
Yes... by a solid 10 degrees. I cleaned the radiator (which wasn't really that dirty) and put on a new oil cooler. Seemed to make a pretty big difference, and I'll tell you, I am MUCH harder on the bike at gingerman than I am at BHF.