how high is ok for EGT and for how long

[needbigtruck]

I know that there has been threads about this before, but I have just bought a 31 foot travel trailer and pulling it on mostly flat land has resulted in going into the red zone on my EGT gage. It goes up to about 1300 degrees and then steady's out there. There are not that many big hills around here but I am leaving fior Florida on Thursday and I know I will hit a few hills on the way. I've read on these pages that it is OK to go into red for a little while. What exactly is a little while. 5 minutes, or 5 seconds. I tried shifting down into 5th to raise the RPM's thinking more flow would cool the EGT, but it goes up to 1300 degrees anyway, and it seems to get there quicker. I have not modified the truck in any way and believe that it must be OK, since if I didn't have the EGT gage I wouldn't even know it was happening. In other words stock, the engine must have been designed to have EGT's of 1300 degrees. I have been careful to let it cool to about 300 degrees before shutting down. I look forward to all your answers, Thanks RBN

[csimo]

I'm concerned about your findings! If you haven't modified the truck at all (no Juice, EZ Amp, Duramaximizer, etc.) you should not be able to get anywhere near 1300 EGT.

I suspect that you either have a gauge that is reading high (what does it read at idle? Should be around 300 EGT) or you have an exhaust restriction.

To test: First see if you can swap out the gauge with a known accurate gauge. A second way to test this would be to get an accurate tail pipe exhaust temp. on another stock Duramax running in Park at 2500RPM for a couple of minutes. Then compare it to yours under the exact same conditions. If yours is much higher than the other unit then you have a problem somewhere.

I suppose the problem could be in the injection, but that should throw a code on the ECM. I'm betting on a bad gauge reading, and perhaps a collapsed muffler as second.

[needbigtruck]

I sit at about 300 degrees at idle. Cruising at 60 with no load I sit at about 600 degrees. I hope I don't have a collapsed muffler!When I rev to 2500 in nuetral it only goes to about 350-400 degrees.

[WKener]

You shouldn't keep it at or above 1300 for any more than you absolutely have to. A brief run up to those temps is not going to hurt anything, but I wouldn't hold it there any longer than 20 seconds or so... That's my opinion.

[Carli_max]

Have you checked your air filter for obstructions or bad filter? Maybe you should swiss cheese it, as others have done with 2001's. Sounds like you have restriction somewhere. Does your trailer create a lot a wind drag?? Maybe an air foil would help! In the mean time I would downshift further so as to bring the EGT's down. Something doesn't sound right to me!! :confused:

[Maverick]

My truck can hit 1300-1350 with ease in stock form. Juiced up I can peg the gauge at 1500 on level #2. This is all towing heavy of course. I got a JK exhaust comming to hopefully cool things down a bit. Question: Those with JK exhaust, how did you attach the tip(stainless))?

[csimo]

These are strange situations! In stock form you should not be able to exceed 1100 EGT.

Maverick: If you pegged the needle at 1500 EGT then the temp. was actually above 1500. The DMAX should self destruct around 1500 EGT. I assure you that you will burn a hole thru a piston in under a minute at that temp.

1250 EGT is a reasonable maximum temp. if you expect your engine to last, maybe 1300 EGT for very brief periods (under 10 seconds). Anything above that will reduce the engine life very quickly. As I said above... 1500 EGT will cause your engine to self destruct. The pistons are mostly aluminum, and the melting point of aluminum is only 1220 degrees fahrenheit.

I have the Juice as well, and just completed a 1000 mile pull with my 10,000# fifth wheel. I pulled on level 2. No big mountains on my trip, but a few long hills. I have stock exhaust except I've replaced the muffler with a free flow design. I was unable to hit 1250 EGT full throttle up hill for at least a minute straight. I know my pre turbo sensor is accurate... I took the unit to ISSPRO to be repaired and checked.

[ 07-15-2002: Message edited by: csimo ]</p>

[hoot]

I have been telling everyone for over a year now that I can hit 1300-1350 stock, hard throttle, uphill. Nobody said much about it back then.

Takes a while to get up there but while in fifth, she will climb to those temps.

I don't believe anything is wrong and I don't think short 1500 spurts will hurt a thing.

I prefer to keep her under 1250. The acceleration from a stop to 1250 is the full gear range (1-5), well into fifth at full thottle. All these diesels will get up like that if you do the same. (Uphill or loaded)

Maybe some day one of these motors will blow up. Until then.......... :D :D :D


PS. I have read of guys with Cummins and PSD hitting 1600+ at times (modified) without self destructing. Are there any documented trials that prove what temps do to the Duramax? I also tend to believe the Dmax actually will handle higher temps because of the way it's designed, notably, the oil galleys in the pistons that recieve oil from jet nozzles down below. That coupled with the head's ability to remove heat could be a real advantage.

I have heard that the weak link is the turbo. If it overheats, it could loosen the clamp holding the two halves together.

The consensus seems to be 1250...... continuous, not short spurts. What would be a bad idea is to run at 1250 for a long time, then taking it up on a spike.

BROKER's got over 400,000 miles on his. I don't know if he runs an EGT gauge but he is always loaded, running continuously. It would be interesting to know his average EGT.

[ 07-15-2002: Message edited by: hoot ]</p>

[Kennedy]

While a performance exhaust and air filter would definitely help lower these temps, I dont think they are that far out of the ordinary. I think there is a tendency to err on the conservative side.

Haven't had much that could load me down with the Juice installed, but 1350

[hoot]

I'm running no muffler and Amsoil air filter with a swiss cheesed box.

It's possible that larger dia. tires effect egt. I run close to 33" tires.

[csimo]

Here's a good article to read about EGT's and the damage they do to your engine if too high (1300 degrees).

http://www.steves.co.za/wb38.htm

[hoot]

Good article.

Here are the numbers I picked up in the article. 1300 F was never mentioned.

"We also know that 90% of diesel turbos today run with EGT's around 830

[Dave]

What I got from the article was 770c or 1418f is what many diesels run at today. They however feel that 720c or 1328f is the max you should run to be safe.

Stock my truck on a mountain grade with a 12,000 pound trailer will exceed 1300 easily. 1350 is the most I have seen stock. With the jucie it will do the same. I however try to never let it get above 1250.

[csimo]

OK Hoot tell the rest of the story!

Here is the important line from the article AFTER talking about the number Hoot chose to quote.

"In fact, we are more comfortable with 720

[hoot]

"Should not exceed 770C (1418F)"

"more comfortable with 720

[6600 Duramax]

csimo

Have to know what dealer in the St. Louis area did that for you. I have been reading about but didn't know who would take care of me. Also what proof or information did you take to the dealership with you. I would really like to have this done.

Thanks

Sorry no comments on EGT

[SoCalDMAX]

I posted this info in another thread a while back and it didn't raise much interest. It was an identical question raised on the TDR forum about what's a safe EGT. The consensus there was about 1250 or 1300* being safe for sustained periods. I think they're all trying to be on the safe side. this is a quote from one of the posts over there:

"Although my pre-turbo EGT never goes above 1100 degrees I suspect that as high as 1500 degrees could be sustained if all other temps are in the green. I'll tell you why I think this.

I operate an aircraft with a turbocharged aircooled 310 HP engine. Being all aluminum except for the cylinder barrels, crank, cam, etc. these engines require great care with respect to operating temps. Surprisingly, the allowable values given the aluminum heads are quite high:

Cylinder head temp - 460 degrees max. Normal 350-380 degrees
Tubine inlet temperature (pre-turbo EGT) - 1650 degrees max

Normal operating EGT runs about 1500 degrees.

Anything above 1650 degrees and you are at the point where the metal begins to literally sag. You don't want to go there.

I realize there are some differences between a Turbo charged liquid cooled diesel and a gasoline powered aircraft engine, but the basic metalurgy of the turbocahrgers is the same.

Personally, I subscribe to the theory that cooler is better. Engine components will last longer. If you want to get 300,000 miles out of your Cummins I would suggest that the 1250 degree EGT limit is a safe conservative limit."


now I realize that the Dmax is not an all aluminum air-cooled engine, but being a watercooled engine with oil jets cooling the pistons and with aluminum heads, it's capable of dissipating heat from the combustion chamber (and to an extent the piston crown) faster than a Navistar or Cummins. Notice the temps quoted, 1500* normal EGT operating temp, cylinder head temp. 350-380* normal.

So while the EGTs exiting the chamber may be 1500*, the intake charge is cooling the cylinder head and piston and the concept that the internal parts are as hot as the exhaust gasses are false. I agree that, generally speaking, 1500* is to be avoided for long periods on a diesel. The Dmax is the only one I know of with oil jet cooling and aluminum cylinder heads. I'd really like to hear if the Duramax corp. did any destructive testing to see what it could take.

I recently saw a video of a twin turbo Porsche getting the living tar tuned out of it on a dyno. The turbos visible underneath glowed red then bright orange very quickly! When the driver let off the throttle, the excess fuel burned in the exhaust and it spit some good sized flames out the rear, but it sure didn't look/sound damaged!

I am in no way encouraging anyone to run at sustained EGTs of 1500*. I'm just bringing some info out that may shed some light on this subject. This is what some aircraft mfrs may consider to be normal operating temps.

Regards, Steve

[TLA]

csimo
Could you elaborate on the install? Is this a warrantee item? I was going to do it myself, but maybe the dealer is a better bet (maybe not????).
Thanks
TLA

[csimo]

There is an article in the July 2002 GM Tech Link newsletter that goes out to service managers. The article is under TAC Tips.

The article talks about the updates to the Allison TCM for shift busyness. Here's the exact text under "Recommendation / Instructions"

"A new TCM calibration has been released to improve the shift busyness. The TCM calibration is available on TIS 2000 version 3.50 or later (released 3/24/02).

The calibration also contains a feature which allows 5th gear to be disabled/inhibited if desired. To make this feature operable, the following items must be obtained and steps performed:"

The parts list follows and instructions on connecting and mounting the switch. My dealer said he was unsure if this was supposed to be free or not, but he didn't charge me.

The way it works is that you hit the switch once (it's really a push button) and 5th gear is locked out, then press it again and 5th gear is enabled. I've found it quite handy.

[6600 Duramax]

csimo

Hey still wondering why you didn't post dealer name. It would be gratly appriciated as I am also from the st. louis area and would like to have this done without alot of hassels.

Thanks

[hoot]

I have seen a turbo glowing red at night on an older Volvo car. It was normal. I believe the exhaust exiting the exhaust ports is still going up in temperature.

The Dmax with aluminum heads and the oil galleys in the piston crowns fed by jet nozzles makes all the difference in the world as far as the block-piston-heads are concerned. It's also good having the water cooled turbo. I believe GM/Isuzu designed this engine with the higher EGT's being accommodated and the larger bore -vs- stroke may be part of the equation. They have purpose for those initial design spec's and we are just beginning to realize what a great engine this thing really is.

[csimo]

"Hey still wondering why you didn't post dealer name"

The dealer was Modern Auto Co. in Washington, MO. A small friendly dealer!

[6600 Duramax]

Thanks csimo

I plan on calling dealerships around st. louis until I get one to cooperate.

Thanks

[Animal]

Posted by SoCalDMAX, "The Dmax is the only one I know of with oil jet cooling."

The Cummins engine has piston oilers, and the max EGT's per the factory is 1250 deg. Many TDR members run 1800 deg. for the 1/4 drags with no problems reported.

[ 07-19-2002: Message edited by: Animal ]</p>

[hoot]

Animal,

You're correct. I believe all well designed diesels use oil spray cooling. SoCalDMAX should have been more specific in that the Dmax has the galleys in the piston crowns. That is unique and quite an advantage in helpng to control heat at the crown. The jets are aimed to hit holes in the underside of the piston, forcing oil to shoot around the insides of the pistons.

I just read an article in the July Four Wheeler mag page 18 that was saying how the big three are all devoting a lot to diesels and trucks nowadays.

They made a huge mistake!!

"The company plans on incorporating it's newly revamped PowerStroke 600 in the new heavy duty F-Series line. With 350hp and 600 lb-ft. of torque, the new version of the Powerstroke will be the only diesel engine to boast four valves per cylinder"

It should have read.... "The last diesel engine to boast four valves per cylinder"

I hate those kinds of stupid screwups.

Cummins was first with four valves, then came the Duramax. The PSD is playing ketchup.

[ 07-20-2002: Message edited by: hoot ]</p>

[schnier]

I work with a guy who has a D***e diesel and he runs his about 1400 degrees while pulling his race truck up hills fast, and said he had it up to 1800 degrees for several minutes one time. The truck has 130,000 miles on it and still runs good. He was running bigger injectors and a high performance turbo on a 1995. I do not recommend this or endorse it, but they do run hot some times with modifications.

[Amianthus]

There was a time I thought I melted my engine. I held the Cummins recommended limit of 1300 degrees as gospel. And I treated it such that I thought that if I hit 1301*, the engine would instantly detonate. So I never broke that limit if at all possible. Well, during our first dyno event, we ran my truck on the dyno too long without letting it cool down. I thought I melted it. :( And man let me tell you I didn't want to go home to the wife to tell her that I blew up our 1yo truck. I sampled the oil, turned out to be just fine (sampled it just 200 miles earlier). The truck was run with the EGT meter pegged (1500 degrees) for around 30 seconds :eek: :eek: :eek: !!! And my coolant temperature hit 220*. It had never been that hot. EVER! We estimate my engine was around 1750 EGT during that run. While considering hari-cari, a TDR buddy told me of a fellow that runs over 2000* EGT during a sled pull :eek: ! That made me feel better. That and when the oil sample came back good, I felt much better. So much so, that I put propane on the truck. :D

My point is that you can jump above the limit for a little while. 1300 degrees pre-turbo seems like a good number to stick to. But when you do that, you're on borrowed time. You'll have to let it cool down or you can risk losing the engine. Aluminum or not.

[SoCalDMAX]

Hi Guys,

Sorry for the wrong info, didn't mean to mislead anyone. Thanks for the catch, animal and Hoot!

Great info Amianthus! I think a lot of us feel the same way, I'm not about to tell anyone that it's safe to go higher, even tho I'll do it with my own truck.

In another post, someone mentioned losing most of his oil in less than a mile and blowing the turbo up. I guess there are some things as or more dangerous than heat!

Regards, Steve

[Southard]

Pulling a tall 5th wheel with a large frontal area I have seen my post-turbo egt go to 1100 degrees. This only happens when I am running in to a headwind and am keeping the pedal all the way down with the tranny staying in 4th.

Most of the time the egt runs 800-900 degrees while towing this trailer.

So far I have 43,000 miles with probably 80% of it while towing.

[01_Duramax_Dually]

I just got back from a brutal tow to Vegas. Temps in the desert were 115-118 and it was 112 in Vegas for the entire time I was there. I towed my 11K trailer and my EGT's routinely saw 1250. My truck is 100% stock..No mods other than the gauges to monitor Boost and EGT. The truck performed well. Gas mileage was way down as air quality was poor(weather station showed 6500 ft with 65% humidity) and for whatever reason the tranny did not want to stay in 5th liked 4th alot and with that came 2500-3000 rpm which dropped mileage(I usually get 12.5-13, only got 9.8-10.1 this trip)
I ran with AC on 3 the entire time and had to climb up some 7% grades for extended periods of time(Mojave to Barstow and Barstow to Stateline) Coolant temp saw 220, tranny saw about 210.

I was easily able to cool things down on the backside of the grades however since the outside temp was so high it took a long time. What I am getting at here is that the EGT's can obviously run higher based on outside temp and how efficiently the inlet air can be cooled by the intercooler. The location of the turbo does not allow it to get much air and with coolant temp at 220 and with it being 115 outside cooling it down is not easy. I have made the same trip with 85 degree weather over the same grades with same trailer and only saw EGT's of 1100 for short periods of time and it cooled down very very fast.

From my racing experience with a supercharger we never let the EGT's exceed 1300....although that will not "MELT" anything, it is hard on internal components. 1500+ is where Melt down will start.

Just my .02 worth

[ 07-23-2002: Message edited by: 01_Duramax_Dually ]</p>