Safe EGT limits, and what damage occurs if exceeded?

[Legal Eagle]

I have been seeing a lot of discussion about 1300 degrees (or thereabouts) being the upper end of the "safe" limit for pre-turbo EGT. That is what the fancy colored arcs on the ISSPRO guage tell me, too. I don't doubt it, but neither do I understand it.

I seem to remember from some of my undergraduate studies that the melting point of certain forms of glass is not all that far from 1300 degrees, and that of mild steel is maybe even another thousand degrees higher. I have got to believe that the alloys used in modern turbos are able to easily withstand temps that would melt mild steel. Why is it that we get worried when the EG temps are in the glass-melting range?

Now, to be certain, I am not intending to run the temps up as far as they will go to conduct an expensive experiment on my X-car. I watch the pyro guage VERY closely and I push it into the yellow very rarely. I never let it get into the red. But I believe I could get EGTs into the red for significant periods of time if I just kept my foot on the floor.

There may be circumstances ripe for "pulling out all the stops". If I need to save a life, I don't mind damaging engine stuff. But it would be foolish to gain a bunch of time on the trip to the hospital just to find that the engine has locked up a mile from the ER. I have had to put equipment at risk to protect lives before, and I always felt more comfortable when I knew the limits of the vehicle and the consequences associated with running past them.

So, I ask you folks where the no-damage / damage line is truly drawn for the PSD. Also, does anyone know how long one can run without damage at temperatures from 1200 to 1300? I pull some long hills with a trailer and I don't want to stay in "yellow" temps if I am sustaining damage.

If one exceeds safe temps, what precisely IS the damage that occurs? Does it melt the blades of the turbo? Will it sieze something up? How long can I keep driving with whatever damage is going to occur?

I know some of you folks out there are really smart on this subject, and I would appreciate it if you would help me become a smarter diesel-driver.

Thanks.

Jay.

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H. J. Ledbetter, Jr. J.D.
"Wife's car" Y2K Excursion LTD, 4X4, 3.73 LS, PSD, 3-guage pillar.ISSPRO boost, Pyro (pre-turbo) Banks tranny temp. Diablo 54. Amsoil air filter. Altimeter. Tows a 30' Sportsmen fiberglass-sided TT w/ slide-out, which likes to go to the mountains a lot.

[BadExcursion]

Legal, It's not so much the turbo that can get hurt when you exceed 1300 degrees it's the valves in the heads. If the EGT's are above the 1300 degree mark, the valves are a few hundred degrees hotter than that. This will not cause melting of the stainless steal valves but will cause the valves to start changing shape. Too much of this can cause a very serious engine failure.

I have a buddy that runs a crew cab dually with all the Hypermax equipment and pulls a 50' 5er. He consistently runs 1300 to 1400 degrees and has never had a problem in 60,000 miles. I think his time is coming as he has to be on the edge of disaster.

I hope this helps and thanks again for lunch last week.

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2000 PSD Excursion Limited 4X4,Deep Wedgewood Blue with beige 2 tone,Graphite leather seats,born in March, 2000, no options left out, Western Diesel Chip, K&N Air filter, Procomp ES 9000 shocks, molded mud flaps, Bug guard, It's a boat pulling fool.

[Legal Eagle]

BadExcursion

I hadn't thought about the valves. Do you mean the exhaust valves?

Does your hot-running friend use the same ISSPRO gauge setup as me? I guess I wonder if his EGT is really that high, or if his gauge is off.

Your welcome for the lunch... and you do have a very nice X-car. Thanks for the ride.

Jay.

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H. J. Ledbetter, Jr. J.D.
"Wife's car" Y2K Excursion LTD, 4X4, 3.73 LS, PSD, 3-guage pillar.ISSPRO boost, Pyro (pre-turbo) Banks tranny temp. Diablo 54. Amsoil air filter. Altimeter. Tows a 30' Sportsmen fiberglass-sided TT w/ slide-out, which likes to go to the mountains a lot.

[BadExcursion]

Yes, the exhaust valves will run a few hundred degrees hotter than the egt where you are reading it. That will be where the 1st failure will most likely occur. My buddy is running an Autometer pyro in approximately the same place you are.

Talk to you soon.

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2000 PSD Excursion Limited 4X4,Deep Wedgewood Blue with beige 2 tone,Graphite leather seats,born in March, 2000, no options left out, Western Diesel Chip, K&N Air filter, Procomp ES 9000 shocks, molded mud flaps, Bug guard, It's a boat pulling fool.

[Legal Eagle]

Bad -

Ok, thanks for the info. That makes sense. I would like to see that guy who is running all those hot temps I have been hearing about, without damage.

Thanks.

Jay

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H. J. Ledbetter, Jr. J.D.
"Wife's car" Y2K Excursion LTD, 4X4, 3.73 LS, PSD, 3-guage pillar.ISSPRO boost, Pyro (pre-turbo) Banks tranny temp. Diablo 54. Amsoil air filter. Altimeter. Tows a 30' Sportsmen fiberglass-sided TT w/ slide-out, which likes to go to the mountains a lot.

[Mark Craig]

Legal Eagle,
The first thing to go if you exceed the 1300 degree maximum regularily is going to be the seals in the turbo that contain the oil that lubes the turbo bearings. The seals start to harden and then leak, the oil supplied to the turbo is pressurized oil from the crankcase and will be pumped into the cold and hot sides of the turbo. Dumping oil into the exhaust and the intake side will create major smoke and poor operation.
Mark

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Mark Craig Western Diesel Performance 1-888-621-4006 2000 Crew Cab Dually, 6 speed, 4.10 Limited Slip, Lariat. Toys are Turbo Brake, Turbo Chip, Turbo Gauges A-Pillar Mount, Turbo Foam Air Filter. To view our Turbo Gauges Click here: http://www.zing.com/album/?id=4293506289

[FLIGHT359]

MARK, that is ENTIRELY UNTRUE!!
#1 exhaust valves swell and can scuff and even seize in the guides, seats can crack also...extending into the head
#2 piston rings lose their tension and oil usage, low compression or both can result
#3 pistons can crack, long term slight abuse will yeild a melted path down the side of the piston where the ring gap resides
#4 IF your engine is still able to live throught this around 1900F you will begin burning the tips off the turbine blades of the turbo and killing the seals.>> It is possible to melt manifolds at the temperatures needed to cause catastrophic turbo damage!!

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FL70, 3126HEUI/330hp CATERPILLAR,6spd eaton autoshift
*WARNING this post may be offensive

[This message has been edited by FLIGHT359 (edited 11-10-2000).]

[Mark Craig]

Flight359,
I beg to differ, go to your local Ford dealer (we are there all the time)and ask to see their current pile of turbos. After you see the crankcase oil dripping out of 9 of 10 they have there you can ask them what caused the oil to be in the cold and hot side of the turbo. The answer is the customer (generally with a stock unchipped truck I might add) kept his foot in it and cooked the turbo seals. These same trucks are out on the road with a replacement turbo and running fine. No evidence of damaged valves or piston rings etc. This isn't catastrophic damage as the temps to kill the trubine blades are as you explained, the temps to kill the seals are much lower around 1300 degres. Hope this helps.
Mark

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Mark Craig Western Diesel Performance 1-888-621-4006 2000 Crew Cab Dually, 6 speed, 4.10 Limited Slip, Lariat. Toys are Turbo Brake, Turbo Chip, Turbo Gauges A-Pillar Mount, Turbo Foam Air Filter. To view our Turbo Gauges Click here: http://www.zing.com/album/?id=4293506289

[diesel_doctor]

I have never seen turbo with rubber or any other kind of soft material used as seals.
Most all of them use a tight fit and an oil slinger. They cut threads into the shaft and this combined with high rpm push the oil back.
This is why you can't pressurize the crankcase or restrict the oil drain tube. Then the oil goes out the sides around the wheels.
Most likely the cause of the leaks are worn bearings or coked up return form shutting it off hot.

Generally the damage is done to the pistons. Heat cracks and or melting of the top. Over a long time it will cut a hole down the side around the rings.
I have seen aluminum on turbo blades where it has melted and stuck to them.

At what temp and how long is tough to call. All gauges are different, and put in different places. I like the post turbo setup. Then shut it down at 1050 or 1150 if you feel lucky or in a big hurry.

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2000 lariat SC 4X4, six speed, camper and off packages, TT mirrors, dark toreador red, born 5/00

[Legal Eagle]

Thanks for all the input. It is certainly nice to see all the experts are out there and willing to offer their opinions. I never knew it could be so complicated.

Anyone else wish to weigh-in on this subject? The discussions are very enjoyable... even if the contributors have different opinions.

Thanks again.

Jay

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H. J. Ledbetter, Jr. J.D.
"Wife's car" Y2K Excursion LTD, 4X4, 3.73 LS, PSD, 3-guage pillar.ISSPRO boost, Pyro (pre-turbo) Banks tranny temp. Diablo 54. Amsoil air filter. Altimeter. Tows a 30' Sportsmen fiberglass-sided TT w/ slide-out, which likes to go to the mountains a lot.