Max EGT's

[Jim Fulmer]

Ok I'm going to try this post again! So does anyone really have and answer to the EGT question of how high, how long, What is high and how long I figure if your towing up a mountain then yes watch it and more or less right foot will control it, but what about the 0-+++++Blast what do you fuel to 1250/1300/1400. I realize it set up properly(transmission in my case) it should heat up the cool a bit in the gear change. Has anyone ever done R&D on this, I've seen and rode in big number truck and EGT's wern't a thought cause the guage was pegged but I can't afford to burn it up, just want it to run good, any thoughts?



Jim

 

[Don M]

Jim,



If you are looking for maximum engine durability then running high EGT's is not the best idea. Piston ring wear is of major concern. Cylinder heads can crack as well even with high EGT's for a short period.

The heads generally crack in the area between the valve seats and where the injector nozzle hole is drilled into the head to allow the nozzle to access the cylinder. The area is very thin between the intake and nozzle hole and maybe twice as thick between the exhaust and nozzle hole. These cracks have shown up in engines with stock fueling levels. See, there really is a reason to watch the hillls and the weight you tow even with stock engines.



Piston rings are worn much faster with high EGT's. All that hot gas is really tough on them. Cylinder temps are much higher than the probe is reading in the exhaust strem. The combustion temps can exceed 4200 degrees. The duration is very short and the temps are lowered very quickly as the piston moves.

The turbo charged Cummins use a lame top ring IMO. It is tappered on the shoulder to help ring seal during combustion. It just seems it would wear easier to me. The tapper also slops the top ring groove in the piston out faster.



Prolonged EGT's in the 1250 area seems to be ok for most engines. I have never seen an engine blow up or whatever from runs up to 1500 quickly and back down. I have been way over 1800 I know, but for quick stints and quickly get back out.

The damage is being done slowly and methodically by the heat.

Some guys are exceeding the 1800 mark daily. The damage is occuring, but not fast enough to notice it right away. Slowly the ring seal is going south. . Not fast enough to notice from day to day.

I pulled my head off about 1 month ago and found no cracks that are visable in the thin areas. I have not magnafluxed it yet.

I ran to 1600 or so at least once a week, but quickly got back out of the throttle.



Botom line is: EGT's above 1300 are bad news and the goal is to keep them lower if you can. Every casting is somewhat different and one can crack where the other wont.



Don~

 

[Strick-9]

Jim,



How would one do this type of R&D? Hold 1500° until something melts and measure the time? Rebuild the engine and repeat at 1550°?



My stock head was pushed passed 1500° for several months on a daily basis. Actually it's more like everytime I drive it. When I installed the ported head, I had the stock head magnafluxed. It had about 4 or 5 hairline cracks (<1/2") in it. The head shop said there was nothing to worry about. Every Cummins head they've seen looks the same.



I haven't had a pyro for 5 months now. The day it went out, I could get 1669° after 3-4 seconds of full throttle. It was still climbing. I've actually added a lot of fuel since then. Nothing has melted yet.



0-105 mph all the time testing 1/4's. The most I usually stay in the throttle is about 14 seconds.



Is this the kind of info you're looking for? Joe Donnelly has said he can pull his airstream trailer with 1400° EGT after the turbo if someone irritates him.



I know I'm shortening the life of my engine. I already have nearly 200,000 miles. When it breaks or melts I'll let you know.



-Chris

 

[Jim Fulmer]

Thanks guys I guess the R&D is kida dumb but I'm kinda dumb about these trucks, The ones I have see are Turbo gas motors an I've seen the racepack read out's at 1800+ but they tear them down if there is a hint of a problem. I guess I'll just play it by ear and eye adn see what happens. Don I get what you saying, if you hard on anything it will not last.



Jim

 

[CUMINNTSTRKN]

i remember a article that i read that said the b series was tested at 1350 for 1000 hrs by cummins. i try to never go over 1200 while towing, but i've hit over 1900 for short bursts. i'm worried about the accuarcy of our egt guages.



jim

 

[LarryB]

I had an old diesel mech tell me he could tell how an engine has been run by the color of the exhaust manifold and turbine housing. He looked at mine and said I was not running it too hot but I was definitely working it. He said it should have a slight rosey rust color to it. Too reddish = too hot, too brownish= too cold. Comes with experience I guess. I just thought it was interesting

 

[Don M]

Mine would be extremely reddish



Don~