Consequences of exceeding Max EGTs

[dusthomps]

Hey guys... I got a quick question since I just installed my new gauges about a week ago (note: pyro is pre-turbo). I was pulling about 8000# up a 7% grade today and watched the EGT's climb to about 1150. I've always read not to exceed 1250, but have never heard anyone mention what the consequences are if you exceed 1250 degrees. Thanks for any replys.



Dustin

 

[formula]

1250 is the max safe "sustainable" EGT. That does not mean if you go a bit over 1250 that the engine is going to instantly explode. I've hit 1350 many times, but only for a second or two. As far as I understand this, the effects of exceeding 1250 for sustained periods of time go something like: piston failure/melting, cracking of the cylinder head, cracking the exhaust manifold and/or turbine housing. Basically, the extreme heat weakens the metals to the point where they begin to loose structural integrity. Granted, it'll take some severe abuse to have these things happen.



Sean

 

[R.E. Miller]

I currently work in the industry, and I have seen some ugly failures in a short amount of time. First of all, if you have a pyrometer, you are ahead of the game. Second, your pyrometer is not a total security blanket, I drove a truck that seemingly ran and sounded fine... until we tested it on the dyno, one cylinder, one melted piston, hung in the bore. One the other hand there are people making tons of power with tons of heat, but many prepare for it. Piston coatings go a long way. For what you are interested in, I would say that watching your gauges and exhaust pipe are really great ideas. I have ridden in some "bombed" trucks, and have watched the egt's go well over 14-1500, but not for a long period... . period. I have tinkered with my truck for a while to get the power/smoke/mileage/egt's/boost tuned to where I like it. Am I done, nope, but I'll continue to self-engineer more power until new trucks are free



Good luck, and just keep thinking 1300 is my the devil :-laf



Russell

 

[BushWakr - RIP]

1250*F = good to go all day (allow sufficient cool down)

1350*F = 1 minute in 5 ( more cooldown time)

1500*F = any second it's going to get ugly, think Chernyobl. .



Now this is not to say that short excursions into high temps can't be done, but when you hit the upper ends, you are actually into temps that begin to change the molecular structure of alum, iron, and alot of things.

Generally playing with fire. ... so to speak.

I know for example, that nascar mark has run some pretty lengthy durations at 1500*F PEGGED :--) :--)

In fact, recently I got a tad toasty myself, and my gauge goes to 1800*F...



He seems to have suffered no ill effects, but I'm the kind of guy who seems to be prone to Murphy's Law, are you?



Ok last bit here, if you have upped your governed limit to say, 2900-3000RPM then you can afford to drop down a gear, bring the RPM's up, the temps down, and still haul apples uphill at good speed.



bob.

 

[dusthomps]

Thanks for the info guys... . that was just what I was looking for!



Dustin

 

[cwienenga]

our local Cummins NW mechanic told me if you overheat and seize a piston the block is junk and that sleeving cylinder hasn't been successful for them when they have tried it for the long run.



cliff

 

[BushWakr - RIP]

Yup, heard exactly the same thing... watch your temps is the lesson for the day...



Bob