Engine/Transmission (1998.5 - 2002) exhaust temps

[travis97cummins]

last night was pulling flatbed trailer with 4 combine tire on it down the very soft gravel road truck shifted into overdrive and exhaust temp climbed from 600 to 900 very quickly pushed overdrive off and temps went back down to 600 wasn't in the throttle very much either boost went from 10 down to 5 and then back could there be a problem or maybe normal cause of the extra pull the soft gravel road

 

[Missouri Mule]

I suspect when it went into OD it made the engine/trans work harder (OD less hp/tq then lower gears to wheels =less traction))and I suspect you did not give it more go pedal. When it was back in 3rd the trans took the pressure off the engine.



Of course I haven't been on loose ground lately and when I was dirving in farm fields or the roads that ran down the side of them I did not have a EGT or Boost guage and I was in 1rst or 2nd. Driving on hard sufaces and be able to shift when I want to I don't think I have experienced your symptoms.

 

[ata]

What happened was normal. When the tran's went into OD you were LUGGING the engine, RPM's dropped, boost dropped but same amount of fuel going in with less air going through the engine = higher EGT's.

 

[Doug_Janowski]

You do not want to exceed 1300 degrees for over 15 seconds damage to the motor will start to happen. But 900 degrees is normal! You were pushing more fuel then air wich heats up the head and motor! My 01 cummins auto, i have 200 hp injectors and stock turbo (as of now) and when i pull heavy loads i have to keep my turbo spooled up real high!

 

[HBarlow]

You do not want to exceed 1300 degrees for over 15 seconds damage to the motor will start to happen. But 900 degrees is normal! You were pushing more fuel then air wich heats up the head and motor! My 01 cummins auto, i have 200 hp injectors and stock turbo (as of now) and when i pull heavy loads i have to keep my turbo spooled up real high!

Sorry, that is not true. The engine is not going to self destruct at pyro temps of 1300*. I had an '01 HO/6 speed with injectors that I ran at 1300* routinely when pulling trailers up long grades. Some advise against it but it never hurt mine.

 

[Tractorat]

I've seen the "15 second at 1300 degree rule" on the tdr many times. When I got gauges about a year ago, the very reputable shop that installed the gauges also warned me to not exceed 1300 degrees. ( I'm pretty sure that I have not approached that mark since getting the gauges, but I may have prior to gauges. On one 10% grade back in maybe 2005 (?) down near Jackson Hole, I couldn't get the truck and trailer past 35mph. The engine temp was starting to creep beyond the first hash mark, so I turned around and went the other way. (I think a thermostat resolved that heat problem). If I ever did approach or go beyond 1300 degrees, thats probably where I did it. Although I do remember going up another hill in Wy a couple of years ago (w/o gauges) and I was concerned that I may have approached or gone beyond 1300 degrees then. I dont think Ive caused any engine damage. Truck still runs and sounds fine.



I wonder where the " 15 second at 1300 degree" advise came from. Did cummins advertise it ? Im pretty sure it wasn't dodge since they say you dont need gauges.

 

[HBarlow]

I've been hearing it ever since I joined TDR. It is basically an old wive's tale. It is based on the claim that aluminum will begin melting at 1300* and the pistons are aluminum so they'll melt. I'm telling you, that simply is not true.

The top of the piston probably "sees" 1300* but only instantaneously at time of combustion in a running engine. The piston is surrounded by a cooling water jacket and has engine oil squirted on the underside, also for cooling.

My '01 had RV275hp injectors installed when it had 6 or 8k miles on it and still has them in it today with about 365k to 370k on the same engine, never overhauled. It would easily cause egt to hit 1600* with a quick flooring of the throttle pedal on a grade.

I have posted many times in the past - I am fully aware that knowledgeable people like my friend Bill Stockard, Joe Donnelly, and others advise against it but for 325,000 miles that I owned that '01 I put my foot to the floor on long steep grades with trailers on and let it pull in sixth gear with the egt at 1300 to 1325*. I never backed out of it unless egt continued to rise or the engine couldn't hold 1600 rpm. If the tach continued dropping I backed out of the throttle and downshifted to fifth. Many times the pyro pegged at 1600* for a second or two before I backed out of it and held it at 1300*.

I know that working it that hard probably causes added wear and may cause premature failures, dropped valve seats, dropped valve heads, cracked upper rings, or worse but that never happened. That old engine still runs great today after the treatment I gave it.

The 2004. 5 and later which are the same basic design and using similar pistons, valves, cylinder heads, etc. were designed to operate long term at 1425* under full power, full load conditions. They use valves etc. designed to tolerate the higher combustion temperatures.

The engines are a lot tougher than many think they are.

 

[NIsaacs]

I run my three Cummins trucks the same way Harvey does, only even worse, (gasp) my pyro is post. I don't allow temps over 1,000, but will pull all day long at that temp.



Nick

 

[Bob4x4]

I have seen many fried engines with and with out gauges and am not one to choose a safe temp for some one elses engine. Piston cooling has come a long way since the 12 valve. If the cylinder temps were all even it may be easier to choose a temp but the pyro is only an average. Most engines will vary from cylinder to cylinder.

I can say that my old 12v has seen some time on the strip,hooked to a sled and climbing outrageously long steep sand dunes with a 1500 degree pyro pegged.

How ever you won't see me doing that on a long grade towing,it is unnecessary.

 

[JMcCoy]

If the cylinder temps were all even it may be easier to choose a temp but the pyro is only an average. Most engines will vary from cylinder to cylinder. QUOTE]



This is very important to consider. Engine builders/"experts" were probably asked to put a number to what is considered safe. One engine may be different from another and I'm sure a little cushen was added.

 

[Midnite]

Travis, is your pyro probe mounted in your exhaust manifold, or in the pipe after the turbo?