EGT recommendations from Cummins.

[rashwor]

I sent Cummins the following question:



I recently purchased a 2005 Dodge Ram 3500 Cummins Turbo Diesel (325

horsepower 610 ft-lbs of torque) powered truck. I am very happy with the

Cummins and the truck. Can you please answer a question for me?



What is the safe maximum Exhaust Gas Temperature (EGT) limit of the

engine?



Here is their response:



Under full load, most Cummins engines produce exhaust temperatures in the cylinder about 1300 degF or so, on the engine dynamometer. In the Dodge Ram application, it is not likely the engine could be ran at 'full load' operation in the chassis but if it could (or if overfueled), the exhaust EGT ahead of the turbocharger should not exceed the 900 to 1100 degF range. The exact temperature will vary on different applications with different pyrometers and the location of the temperature probe.



The pyrometer measures exhaust temperature and the probe is usually mounted about 2 to 6 inches from the turbo outlet (after the turbo) and in that area the exhaust temperature under 'full load' conditions should be in the 700 to 900 degF range. The pyrometer probe could be installed ahead of the turbo for maximum exhaust temperature out of the cylinders (900 to 1100 degF), however, if the probe ever fails, it goes directly into the turbocharger and will likely cause a catastrophic failure of the turbocharger, plus additional engine damage.



My thoughts:



1) I was under the impression that as long as we were below 1250* pre-turbo, we were good and probably are, but they recommend not exceeding 900* - 1100* pre-turbo. I will stick with my 1250* rule.



2) The question and answer "Powermaster" does not know much about what we do with our Rams as far as the loads we pull with them.



3) The question and answer "Powermaster" does not know that in the Ram application it is possible to exceed the pre-turbo EGT limits they recommend with a stock truck and no cargo in or towing.



4) What I was really searching for in asking the question was if the 325 engines had moved up any on the acceptable EGT limits since you can exceed those limits with a stock truck with no load on it. Doesn't look like it.



Your thoughts welcome.

 

[nickleinonen]

stick a pyro on you 05 bone stock pre turbo, and you'll be able to get +1300°f ... what's cummins' answer to that?

 

[RustyJC]

My 2nd generation HO would hit 1300 degF pre-turbo EGT towing our previous (lighter) 5th wheel when the truck was absolutely stock. If Cummins thinks these engines can't be loaded up except on a dyno, they are sadly mistaken! As many Cummins diesels that go into trucks, you'd think they would know about dragging trailers up 5 mile 6%-7% grades at maximum GCWR (or above) - I'll put that up against a dyno any day.



I think what you're seeing is a response from a (let's be charitable here) "less than experienced" young engineer or techie sitting at a customer support desk. Notice that he is taking Cummins' preferred post-turbo EGT's of 700-900 and just adding 200 degF to come up with the 900-1100 pre-turbo EGT's. Those who have had probes mounted both pre- and post-turbo have reported actual delta T's of 500 degF between the probes at full load, so that 900 degF post-turbo EGT that Cummins cites could be a 1400 pre-turbo EGT. I wonder how Cummins would feel about that?? :{



Rusty

 

[JVolpe]

My 04. 5 325/600 bone stock would hit 1350 and stay there on WOT. Pyro top of manifold between 3 & 4.

 

[WStoops]

Climbing a long 6 to 7% grade at WOT empty I can hit 1350+. Pull a 8800 lb trailer on the same hill it will go to 1450. Completely stock truck. I have to back off considerably to maintain 1300. Probe between #3 & 4, DiPricol gauge.

 

[bpenrod]

I agree the tech was being conservative! I did read some good turbo info on another site. It was more for over the road trucks but thier tech guy said the difference between pre and post turbo temps depends a lot on boost. As the turbo uses some of the exhaust gas heat to power itself they cam up with a formula of 10 degree heat reduction (post vs. pre) for every pound of boost made. So 30 psi boost would lower the temp about 300 degrees. Probably not exact but a good rule of thumb for discussion.

 

[Gary - K7GLD]

ALSO realize there's a BIG difference between temps that are OK on a LIMITED basis, and those the engine might be exposed to regularly in typical operation... I don't worry any about the 1200 degrees or so I see on a hard pull for mere minutes at a time towing our 5er - but might get REAL nervous if that was happening for hours at a time on a daily basis!



Realize these same engines are also used in commercial/industrial settings, and maybe run up against the govenor around the clock!

 

[XJSuperman]

If you notice also cummins said that these engines are NOT fully loaded in the dodge chassis... meaning if you stay within the 'legal' tow ratings etc for your truck you are not using the engine's max capacity... so I would think that 1300* in our truck while not necessarily good... is safer than 1300* in a true medium duty application where the engine is loaded to it's maximum capacties.

 

[Snow man]

Either way the 600s run to hot. That response from cummins was a cop out. Apparently he didnt have the time to answer your e mail correctly,or wasnt qualifed to answer.

 

[klenger]

I think the tech was getting his info from a 5 year old database.

 

[Gonzo 1066]

My 2nd generation HO would hit 1300 degF pre-turbo EGT towing our previous (lighter) 5th wheel when the truck was absolutely stock. Those who have had probes mounted both pre- and post-turbo have reported actual delta T's of 500 degF between the probes at full load, so that 900 degF post-turbo EGT that Cummins cites could be a 1400 pre-turbo EGT. I wonder how Cummins would feel about that?? :{



Rusty

My bone stock (-cat and added Afe)04. 5 with a Autometer probe just above the turbo flange, in the exhaust minifold, near #4 exhaust will easly run 1300 it has been close to 1400!!! degrees on a long hard pull. (6 to 8% grade in the south west) If I was foolish enough to leave my foot in it I suspect it would go quite a bit higher. Here in the Northwest the added humitity keeps the EGTs a easy 100 degrees cooler.

WE NEED A TIMING BOX TO HELP WITH EGTs PLEASE SOMEONE FILL THIS NEED!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[John - K5AWO]

Pre-Turbo probe failure??

..... The pyrometer probe could be installed ahead of the turbo ..... , however, if the probe ever fails, it goes directly into the turbocharger and will likely cause a catastrophic failure of the turbocharger, plus additional engine damage... ...

Okay, the techie is short a couple years of school classes... . But, my question is has anyone ever had the experience of seeing a temp probe failure that actually caused it to break apart?



I have seen them just stop working, but to break apart? I couldn't get the last one I worked with to even break apart so I could get it out of the hole when it needed to be replaced.

 

[Gary - K7GLD]

"my question is has anyone ever had the experience of seeing a temp probe failure that actually caused it to break apart?"



I think the odds of a probe actually falling apart and damaging the turbo are slightly less than winning the lottery... Sure, it probably HAS happeded at one time or another - but so rarely as to be pretty much non-existent - far more likely to damage the turbo or engine from a WIDE variety of other common causes...

 

[RustyJC]

I think the enhanced protection provided by the pre-turbo thermocouple placement far outweighs the miniscule risk of turbo damage due to probe failure.



The large industrial engines our company builds have a thermocouple in each cylinder's exhaust outlet as well as one or more pre-turbo thermocouples.



Rusty

 

[Gonzo 1066]

There has been and continues to be quite a few OEMs that have a pre turbo probe. The one that comes to mind is International Harvesters I-6 466-530 series engines in Agricultural, truck and industrial applications. I have NEVER seen a probe failure in these engines and that includes those running much higher than stock HP levels and into the 8 to 15,000 hour range. This is not saying that it never happened. Just that it is very very unlikley. IMHO

 

[Sarge]

This discussion comes up from time to time, and the last time a member made a good observation. If your running stock (as I am) and the egt's still top out at over 1400* (as mine do when towing) and something happens to the motor, then so be it. Cummins built it, and DC put it together. All the limits and safety margins are spec'd out by their engineers. I bought this truck to work it hard, and get the most of that 325/600 rating out of her that I can. I am fully gauged too, and watch the EGT's hit 1450* while pulling a big grade in 5th gear at 55mph. And the Cummins keeps rolling. If you BOMB it and change some factory specs, then worry. Until then, "drive it like you stole it. " :-laf Sarge

 

[MCrossley]

To answer your question yes, I have I lost a SPA probe pulling hwy 80 with my fifth wheel did not realize the probe actually broke off until I pulled it out when I got to my destination and yes it was a good 1 1/2 of probe that was gone, fortunatly no damage was realized.

 

[Richy]

Thanks, you just answered my question. Just installed an EGT gauge and it will show me 1400 degrees on a hard pull. Before the gauge, I never took my foot out of it nor worried about EGTs. What about Jane Doe public that hauls her five horses and never heard of EGTs. DC still warrants them. Stock 600 6 spd.

 

[robert4570]

I intend to keep my 05' bone stock , with the exception of an egt gauge. If in stock trim i won't worry too much, like Sarge said drive like you stole if stock . Modified , you might have to worry.



What readings are you guys gettin empty on the highway?