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Discussion Starter #1
I can't answer that, but what I can do is tell you about my day. I am driving a 2005 2500HD Duramax/Allison. It has a cold air intake, a 40hp Predator, no kitty, and an aftermarket muffler. I run synthetic oil. I have owned 7 D/A's and this is the first one with an EGT gauge. For those of you that don't know me I deliver trailers for a living. OK, back to today.

The load is 13.5 feet tall and 8.5 feet wide. Gross weight is around 26,000 pounds. I am on 70 in New Mexico, westbound just east of White Sands. It is a gradual climb that goes on for miles, and gets steeper at the end. I noticed my EGT at 4:45 PM. It was 1425*. I do not know how long it had been that hot. The elevation was 3986 feet and the OAT was 75*. Being the DP's Inspector Gadget, I decided to investigate. I put the pedal on the floor. I normally drive like that anyway! ):h The climb to the top took 23 minutes. I arrived at just under 5500 feet and to 58* oat. My ECT was approximate 240*. My EGT was never below 1400* and at one time was 1550*. I saw no problems after the climb. I also have a 2004 with 210,000 miles that has seen this kind of usage since new.

Do I recommend this? NO, but maybe with the oil cooling on the bottom of the piston's that these motors have the EGT can safely run Hotter. Hope this helps.
 

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i believe it is the heating and cooling that wears parts prematurely.

this was meant to be a post, right? not a thread?
 

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What Rick is getting at is the old "standard" said that EGT's should not go over 1250* or 1300* to avoid engine damage, but that the new diesels seem to operate at 1400* or more from the factory without crapping out.

So what is the actual EGT limit?

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what's the difference between immediate failure due to EGT and serious integrity damage of associated parts?


i was confused, there was a thread a couple below us that asked this question, and i figured he was responding to it.
 

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what's the difference between immediate failure due to EGT and serious integrity damage of associated parts?


i was confused, there was a thread a couple below us that asked this question, and i figured he was responding to it.
I know, I saw the other thread too, and it was sorta odd that they came about at the same time. ;)

The difference is longevity, but with Rick driving this way often and having hundreds of thousands of miles on the trucks that he is doing it on, we can rule out the "immediate failure" part and just about say the "serious damage of associated parts" has yet to surface in more than most peoples truck life of driving, making it a non-factor as well.

So, again, are the old limits of EGT no longer applicable to todays diesels?

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...maybe with the oil cooling on the bottom of the piston's that these motors have the EGT can safely run Hotter. Hope this helps.
"safely" at the expense of other components that are not too happy with your oil, now 340 degrees.


I have a LB7 turbo, from a tow vehicle, in front of me, It never saw over 1400. Turbine and bearings are toast. It appears the turbines started folding first. The bearing is totally gone. The turbine shaft sheared, but it appears that was after the bearing failure. (bearings fail when unlubricated and hot)

I can tell you that oil designed to lubricate at 100 C (210 F), isn't worth squat at 340 degrees. Film strength is reduced to nothing, close the waters consistency, only slightly more viscous. Metal-metal contact is more prominent, as is asperity wear and tear given the reduced clearances between parts that rely on float.

ALL WEAR in this vehicle is heat related, and it all begins with cylinder head temps. After 2/3rd of the combustion heat is routed through the exhaust, the remainder is conveyed to other parts via oil and coolant, through mechanisms of convection, conduction and radiation.

Rick, Don't you see lower egt's when the the truck is not heat soaked, let's say at the bottom of a climb? Why do they "creep"?

What can lower egts. Some things I can think of (that we can control): lowered charge air temp, lowered coolant temps internally, lowered oil temps, correct timing, exhaust restrictions

Some, you have done (I would really like to see the new downpipe in action). Which ones are left?

"oil cooling on the bottom of the piston's that these motors have the EGT can safely run Hotter."
 

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i believe it is the heating and cooling that wears parts prematurely.
I agree. The larger and more frequent the cycle, the more damage occurs, at the molecular level, crystalline formation.

So reducing the highest temp seen by the part (turbine in this case for egt) reduces the magnitude of thermal cycle. If the turbine could be kept hotter when unloaded, this would be good also. Or at least slow down the cooling. Going from 1500 (sustained) to 600 repeatedly surely makes the turbo unhappy.
 

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Discussion Starter #8
nosliw, yes I meant this to be a thread. It was just a weird fluke that the other thread happened at the same time.

kb asked; Rick, Don't you see lower egt's when the the truck is not heat soaked, let's say at the bottom of a climb?

I respond; No, the EGT is a direct result of "power being used", and by slowing down or "cresting the hill" I can lower it.

kb said; Some, you have done (I would really like to see the new downpipe in action). Which ones are left?

I respond; What new down pipe? The BS gives me the most benefit in EGT's, but my tranny will not hold up to it also when loaded that heavy.

Sorry about the format guys. I have limited service this weekend and had to do this in notepad.
 

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Rick your story sounds very much like my own. I have resorted to downshifting and keeping RPM,s at or around 3000 and backing out of the throttle to keep EGT's around 1250. This also seems to keep ECT's at or below 230* depending on ambiant temps mostly. I pull a High profile 5er at about 13000 with a combined at about 22000. Have you ever pulled with stock tuning and just the boost stick. I wonder what that would do to your tranny?
 

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Discussion Starter #11
The BS and stock tuning doesn't seam to do much for me towing. I think the best thing for me to do is a tranny upgrade so I can run the power of the Predator with the BS towing. Maybe even the 65 hp setting with the BS.):h
 
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