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Discussion Starter · #1 ·
Due to recent familiar bickering, not nearly as much will be posted here as would have been, which is a shame. My thermal mapping project is wrapping up now, its been interesting to say the least.

Below find a neat chart. The chart shows EXACTLY why we overheat (I am 99% sure it does anyway).

IMO, which is worth what you pay for it so please don't bother starting an arguement about it, all other current efforts will not accomplish what they plan to accomplish.

PUSU-2 if it occurs may bear this out here in 3 months or so.

As I bring in the fix I will be posting more showing the improvement. Its not going to be an instant thing, as in tomorrow, but generally I am aiming for a major step each weekend. The main reason it isn't instant is because it takes hours to make the changes (they aren't small) and I have backed the truck down to completely stock. The objective is to be done before summer is here and all our trucks get the yearly meltdown. As of now I think there is only one main step to take, so it may be a short trip, except it isn't exactly an easy thing to do. :)



Game on! :D

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Discussion Starter · #3 · (Edited)
You know there is :D

Too bad thats part of the "not nearly as much will be posted here as would have been" part.

Below, same series of runs, ECT plotted. As you can see, it was relatively easy to achieve 245* without much effort. This will be the baseline target to beat. When those steep climbs are eliminated, then we are home free. Future charts will be similar to this one, showing the single tracked point unless something else needs to be pointed out.

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Discussion Starter · #4 ·
Oil temps

I have been monitoring oil temperature and have run across a wide discrepancy between my measurements and info posted previously.

Dropping our oil temperature lower would appear to be a bad thing, unless someone out there wants 140*-150* or even colder oil running through their Dmax.

The 250* or so peak range as shown at PUSU appears correct, in an overheat condition (lets say 240* ECT and greater) we can reach that briefly, but thats pre-cooler and the return oil is much lower. That oil temp WILL NOT stay around without the engine load remaining at max, the least little let up and it drops like a rock. Once the engine gets hot everything goes hot with it, oil included of course, and they all hang around each other fairly closely temperature wise. If you are not overheating you will be wasting money for sure adding any oil cooler to your Dmax with the intention of dropping your oil temperature, in fact lower will be bad for you 99.9% of the time.

Fingers: Are you sure your internal pan measurements weren't a vapor temp in the pan? Perhaps thats the stratification you were talking about? Figures of 320* or even 360* were mentioned somewhere, I just can't see where the actual liquid oil itself is getting anywhere near that, even with the ECT over 240*, and I know I am getting accurate temp readings.

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First, I don't have this situation with my truck, but I find your analysis facinating to read.

Second, from what I have read in this thread, is what you're saying, the engine oil to engine coolant, cooler appears to be working, just not capable to tranfer enough of the heat under thermal load?

If yes, would this mean a higher flow rate of coolant, greater surface area in the cooler, or both would be a potential fix?
 

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Discussion Starter · #6 · (Edited)
First, I don't have this situation with my truck, but I find your analysis facinating to read.

Second, from what I have read in this thread, is what you're saying, the engine oil to engine coolant, cooler appears to be working, just not capable to tranfer enough of the heat under thermal load?

If yes, would this mean a higher flow rate of coolant, greater surface area in the cooler, or both would be a potential fix?
Well, not exactly. The cooler works great, it is very efficient. Even when oil into it is 250* oil back into the engine is only 220*ish. I have even seen oil into the engine remain about 200* even though ECT hit 245*, so in essence its the little cooler that could, but even it can't do its job if the engine coolant bails on it.

It of course uses engine coolant to cool the oil, so when the engine coolant soars to 240*-250* such as in an overheat condition then your ability to cool the engine oil goes out the door. Anyone can see that 240* engine coolant will not cool 200* oil.

So it isn't that it isn't capable of cooling, its ability is removed because its cooling media (engine coolant) has been heated beyond cooling usefulness.

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I see, I had it backwards.

The chart that you have displayed, and please forgive for not completely staying up-to-date with your post, shows two disticnt spikes, with several moments of rapid rise and decrease "mini-spikes."
I was curious if this could be correlated to actual engine rpm. Could this be impellar cavatation? Or has this already been ruled out?

Sorry, don't mean to be an armchair quarter-back.
 

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Discussion Starter · #8 ·
Questions are always good, keep 'em coming.

The big spikes are when I kept the load constant for the duration, the mini-spikes are burst runs just to get stuff moving around. In other words, blast from 20-60mph a few times, or in a bigger one from 20-100mph perhaps.

Personally I have ruled out impeller cavitation. Others may think its happening, but my money says no, especially when I can make it happen down at 2000 rpm just the same as 2500 rpm.

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But wouldn't the same cavatation that would occur @ 2K also happen @ 2.5k?

In otherwords, 2k is the threshhold for cavatation to begin. I know that with boat props, as soon as it begins, there only one way to remove it, slow down the rpm.

Is there other data that was in the original graph, or are all of thoses ECT readings?

Is there a way to overlay engine rpm over top of the measured ECT to determine if there is a correlation?

A correlation either between impellar speed being too fast or too slow.
 

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Fingers: Are you sure your internal pan measurements weren't a vapor temp in the pan? Perhaps thats the stratification you were talking about? Figures of 320* or even 360* were mentioned somewhere, I just can't see where the actual liquid oil itself is getting anywhere near that, even with the ECT over 240*, and I know I am getting accurate temp readings.

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Wet Thermacouple in the oil. Yea, saw 320* frequently and a spike to 360*. Running high revs. The spread between oil temp and ECT seems to get bigger with higher Revs. 2800 to 3000 RPM Vs 2100 RPM at PUSU. Work load shows up in the oil temp almost instantly.

Super cooled oil is not good, but by using a thermastat bypass you can keep it close at 185* which is almost ideal.

Jon
 

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Discussion Starter · #11 ·
Considering our RPM range is maxed at 3250, if we are cavitating at a lowly 2000 rpm then we have big problems.

Here is some info to help you:

At PUSU at 2100 rpm we measured 10psi or so on the suction side and around 25-30psi water pump outlet. We also measured 50-55 gpm flow through the upper hose, max flow is about 70gpm.

Its not cavitation.

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Discussion Starter · #12 · (Edited)
Wet Thermacouple in the oil. Yea, saw 320* frequently and a spike to 360*. Running high revs. The spread between oil temp and ECT seems to get bigger with higher Revs. 2800 to 3000 RPM Vs 2100 RPM at PUSU. Work load shows up in the oil temp almost instantly.

Super cooled oil is not good, but by using a thermastat bypass you can keep it close at 185* which is almost ideal.

Jon
I haven't stressed it to get max oil temp, but I do know soak has a big impact. 25* increase in backup runs, I'll try run 3 and 4 and 5 perhaps to backup your data.

I agree 100% with the rest of what you said.

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OK, not to sound like the village idiot, but I am anyway. Why, because I am new, and miles behind on the learning curve.

3250 rpm, is this the water pump speed, or the engine? A pulley could potentially throw off the desired speed of the water pump.

PUSU- ?

My background is not engineering, or the hard sciences for that matter. But it would appear to me that unless the supply side had an ample flow, at least the same flow as the outlet, then you are correct. Has there been a study to determine resistance to the flow on the inlet side? If there would, it might not be a lack of suction, or cooling capability, but just lack of supply.

on edit- I know that you have probably already considered this, I am just trying to help.
 

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Discussion Starter · #14 ·
Since the system is more or less a closed loop, the supply side has the same flow automatically as the pressure side. It may be at a different pressure but the volume remains the same.

In other words, if 55 gpm is being measured continuously out, then there is no choice except to have 55gpm in as well. There is no other place for the coolant to go, it returns to the "suction" side pressurized.

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Discussion Starter · #15 ·
PUSU = Put Up or Shut Up

Look for the PUSU threads, it was dyno testing looking at the overheating problem concerning the LLY Dmax trucks.

Lots of reading for you to do, especially in the overheating threads. :)

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True, I have a lot of reading to do, done a little, but not nearly enough.

Here are some assumptions I would like to verify:

1. It's not a geographical issue.
2. It's not isolated to one particular model year.
3. It's not a false positive reading, ie faulty sending unit.
4. The components that make up the cooling system did not have short run manufactures, hence different tolerances and possibly different components all together.
5. It's not component failure.
6. It's not coolant related.
7. it's not engine oil related.
8. It's not an engine wear issue.
9. It's not a fuel issue.

Hypothesis:

Faulty manufacturing process
Faulty engineering design
Failure to follow engineering design specs
 

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Discussion Starter · #17 ·
You nailed it.

#2 sorta. Its the LLY Dmax.

Hypothesis: also accurate.

It is "Faulty engineering design". The piston/head design is the problem. And it will NEVER be fixed by GM.

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So if its the head design, is it the size of the cooling cavities that is not allowing enough flow?
 

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Discussion Starter · #19 ·
No, the flow is there. Remember, we have measured it, and the literature says they increased flow in the LLY cylinder heads. I believe that, and as it turned out that was a bad move in this case, especially when coupled to the new piston design.

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So it's moving so fast that it is unable to absorb the heat from the head, or theres not enough volume. Interesting...


Just another idea, could it be the head gasket? I remember a friend of mine installing a head gasket upside down and on the wrong side, once. It blocked one of the EC channels and had a similar scenario.
 
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