• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Over Temp..."Bubble"

knkreb said:
Diesels run best when warm. They are a "heat engine." Closer to 195, the more efficient it runs. 180F is a band aid to not getting the heat out... it just gives you a little buffer. You've only got a gallon or two of coolant in the system, so 15F won't last long if you are not getting rid of the heat.
Click to expand...

Kevin! How nice to see a post from you.

Hmm. As I understand it, another issue has to do with overall flow. The 195 degree stats don't actually open completely until around 205 degrees. Therefore, at 195, the thermostat is inhibiting flow.

The 180 degree stats are completely open by 195. The strategy I am going with is to use the 180 stat, allow it to completely open, and then use the electric fans with the sensor and controller to control the temp. The idea is that I can get max flow, and use the sensor electronics for the electric fans to control the fan speed and adjust the overall engine temp.

What do you guys think?

-Rob :)
 
I tend to disagree here.

Thw engine is going to run at near 190 anyway in the core.

The 180 stat starts to open at 180 and is fully open and flowing by about 185F or so.

The amount of coolant in the radiator and hoses etc is about 3 gallons and the total capacity is about 6 gallons.

The high temps used (190-195) are to help meet the emissions standards.

The little extra heat is better left somewhere else.

I even run a 180 in the 500HP Cat.

The 6.5 does not seem to have any issue with the 180 stat. Mileage is the same as with the 190-195f stat.

I just prefer to keep the temps down in the 6.5 engines.

In the long run the extra thermal stress is best left out of the equation with these engines.

Once the 180 Stat is open the coolant starts to flow and then the radiator gets into the action.

Overall the life of these engines will be better off by keeping the temps a little more reasonable.

Granted the diesel is a heat engine, but too much of a good thing is not necessarily a good.

MGW
 
Disagreeing with your disagree Robyn :D

Flow is what it is about, and IMO 180 is too cool for the 6.5, IMO also enough differences so that it doesn't matter what works well on other engines 6.5 was designed to flow to maintain 195 whether for emission or another reason.

Bill shared with me some stuff "discovered" when sizing pumps & stats for his balance flow system (no longer for sale/needed), which led to the balanced flow setup with a single stat-pump-clutch-fan currently offered now. I can't recite verbatim what his thoughts on it were, but something like this.

If too cool a medium; flowing too fast; and fan kicking in too early the overall cooling is actually negatively impacted, as your stats cycling open/close, fan in/out are chasing a temperature range, rather than settling in on maintaing a constant temp hence his preference to single stat over dual. Also a theory of Bill's that hot/cold "swings" are a part of the block cracking issue.

It would seem from what Bill & his team found was that GM went overboard with 130gpm & dual stats, Bill's current system flows more than original GM but less than the latest 130gpm offering, I've been running both my rigs per Bill's advice the last 5 years never had a overheat (even towing up to 18K on hot days max I see is 198F), 195 stats are running at Bonneville today so something done rite there evidently.

We used to have similar experience in the USN converting steam to condensate, too much flow of water thru the condenser and no heat got picked up by the water leaving the condenser and you got steam hammer in the bundle, too little flow and you got "cold shock" hammer in the bundle, adjust the regulator for "just rite" and all was good, yet sail to a location with colder or warmer water and you would have to find the the right flow zone again.

Thermodynamics is as much smart experimemtation as science, it's relatively easy to find optimal temp or flow in a fixed flow cooling system, but since the 6.5 is a variable speed/load/heat device makes definition of what works best hard to define. I'm not an expert on it either so by all means if 180F is what works for you run it, 195 set up is what is working for both of mine.
 
I was thinking of our conversation the other day Tim.... maybe we need to prune this off into it's own thread....

I don't think I can wrap my head around this "flow to fast" and not exchange heat idea. I need to look into this further, research it or something if there is a term for it. I can't seem to understand it.

In my industry (refrigeration/HVAC) we have fluids, vapors, liquids condensing and evaporating at various places in the cycle of refrigeration. Increased flow through a heat exchanger still resulted in heat transfer, yet the TD (delta T/or temp change of the medium) through the heat exchanger was greatly reduced. I can increase flow through a water cooled condenser and increase it's heat transfer capacity, but instead of the cooling fluid changing 10F, it may only change 5F from inlet to outlet based on the flow rate. Slow down the flow, and the capacity changes and the delta T increases. Heat is being exchanged, (at somewhat a different rate) but the outlet cooling luid temperature rises.

So, I'm not really understanding the theory of not-exchanging heat.

Compound that with a thermostat that opens and closes based on temperature of the fluid. This is not an electronically controlled solenoid that opens and closes full port at 0.1F temperature change. The thermostats open and close across a range. As the temperature increases, the thermostat port opens further to allow more water to flow. So really, we're not talking about a 130 GPM system all the time. It may be a 5 GPM, or a 50 GPM, or could be at worst a 130 GPM. The thermostat should throttle based on temperature at the thermostat itself. It should use as much cooling as it needs to maintain it's setpoint temperature.

When the outdoor temperature is 15F, you have an extremely oversized radiator for your application. However, at 115F, it may be just enough for the job. The capacity of the radiator is dependant upon the temperature difference between the coolant and outdoor ambient condition. The greater the difference, the greater the capacity.

Something I might want to throw out there for discussion is about what we call "hunting" in our trade. This is where the regulating device cannot keep the process regulated because it has such excessive capacity for the application. One type of problem I have seen is with a water cooled ice machine. When the city water temperature drops in the winter, the water regulator allows too much water through. As soon as it opens, it closes again because the refrigerant pressure that it is attempting to regulate will drop so fast that the water regulating valve will snap shut. It will create a machine gun effect of open/close/open/close/open/close.

The other example is where an expansion valve that is oversized opens so wide open that then it closes to attempt to regulate it's overshoot. Creating wide swings in pressures and temperatures.

Bill may be on to something in that area with thermal stressing....

Make any kind of sense?
 
Last edited:
I'd like to see some chatter on that to see what I'm missing on that with the application of it to a 6.5. Maybe we can make up a "reference material" thread on it once everything is compiled.
 
Well, things get even messier, because the GPM flow is not constant - the water pump is changing impeller speed with engine speed. Bill Heath's article even talks about how as the engine speed increases, we may see LESS flow!

Eep!

-Rob :)
 
Very interesting... that goes against logic too. Faster impeller speed *USUALLY* ends up in higher flow rates. Is that because the impeller is loosing efficiency and cavating -OR- is it because the flow rate increases and the thermostat closes down to compensate resulting in lower flow.

What say to that thought?

Gotta link to that article from Bill?
 
knkreb said:
Very interesting... that goes against logic too. Faster impeller speed *USUALLY* ends up in higher flow rates. Is that because the impeller is loosing efficiency and cavating -OR- is it because the flow rate increases and the thermostat closes down to compensate resulting in lower flow.

What say to that thought?

Gotta link to that article from Bill?
Click to expand...
http://www.maxxtorque.com/spring-2009

See page 35.

-Rob :)
 
Coolant velocity vs heat transfer rate, cooling list

dangerousdave said:
If your transmission is like mine, it drops into a sort of neutral when you take your foot off the accelerator going down hill, slowing the flow of coolant through the rad and engine. Putting it in Drive instead of OD should prevent this from recurring on the hot downhills.
Click to expand...

Simplify; coolant going too fast through the engine doesn't have enough time to absorb enough heat, flowing through the radiator too fast = can't dissipate enough heat, and overheats. Flow too slow, it reaches saturation and overheats.

We're not out to re-engineer the wheel, just keep our precious 6.5s from dieing too soon. What works? That which has and is working for the heated ones driving with loads on grades in triple digits (me):h). Given that each engine and driver is slightly different, some variability is normal.

Seems to me, what works consistently are the following;

1. CLEAN THE COOLING STACK (oil & trans coolers, A / C condenser, Radiator)
2. Clean the fan thermostat
3. Have a properly Functioning pressure cap
4. Later model HO water pump and fan blade
5. Flush the system, get the crud out of the coolant passages.
6. Have a properly Functioning Thermostat
7. Fresh coolant, only one type, (IE not mixed red and green)
8. Distilled or deionized H20 (not tap water)
9. Water wetter (redline or similar)

Did I leave any MAJOR details off? (besides the obvious, like a dead bird or a stack of snow blocking the air flow:mad2:)

To prevent the collection of debris, I keep a piece of window screen in front of the grille, screwed to the grille at top, held at the bottom by the 2 rubber bumpers and the license holder. Much easier to clean and replace. The birds at the rest areas love it, too; "easy pickin's".
 
Excellent post, DangerousDave.

I think you covered everything. I've not used water wetter. Also, I agree on the window screen - I take the front grill off, and then use zip ties to secure it to the BACK of the grill - it can't be seen, yet blocks all the bugs and leaves. Cheap and easy to replace.

-Rob :)
 
Having been out at Bonneville and seeing what some people have put together for speed runs or pit crawling, I have visions of someone fabing up a window screen to a spring loaded window shade mechanism (the roll up type Tom & Jerry cartoons love) suspended in front of the grill and secured to the bumper at the hooks or rubber bumper guards. Maybe behind the grill? Hmmm.:D

Seriously though. Moderators, feel free to skin this thing of my rambling and keep the great flow of ideas to maximize the thread if it suites the forum's needs.
 
TurboTahoe said:
Excellent post, DangerousDave.

I think you covered everything. I've not used water wetter. Also, I agree on the window screen - I take the front grill off, and then use zip ties to secure it to the BACK of the grill - it can't be seen, yet blocks all the bugs and leaves. Cheap and easy to replace.

-Rob :)
Click to expand...

While this is a good idea for the debris blocking, have you ever tried to open a screen door in a 60MPH wind. And so the saga continues.:D
 
96 OILBURNER said:
While this is a good idea for the debris blocking, have you ever tried to open a screen door in a 60MPH wind. And so the saga continues.:D
Click to expand...

No, I haven't tried to open a screen door in those kinds of winds, but I have used a 120 MPH leaf blower on the screen door mesh, and it seems to pass through pretty well. Does that count?

-Rob :)
 
TurboTahoe said:
No, I haven't tried to open a screen door in those kinds of winds, but I have used a 120 MPH leaf blower on the screen door mesh, and it seems to pass through pretty well. Does that count?

-Rob :)
Click to expand...

Thats 120mph out of a 4" hole. 60mph over the entire surface would create restriction. Enough to matter? .... who knows.

I like the 195 t-stats too. For the temp swing reason.

If the engine is ALwyas running at 195temp, and when its workin hard moves to 210 and maintains via fan or self containment, there is only a small temperature swing.

If running 180's, and then needs to work hard, temperature swing can rapidly go to 210 once again, then maintain via fan or self containment.

These numbers are just for reference.

We all know metal can take extreme heat just fine. But it's the temperature change that forces it to expand / contract quickly, which I agree, can defanately stress the block more to aid in cracking.
 
You must log in or register to reply here.
Back
Top