Engine/Transmission (1994 - 1998) Is 1200 degrees pre-turbo OK for extended periods?

[scaryfast]

When I'm coming up the west side of the Eisenhower Tunnel pulling my trailer, I put the exhaust temp right at 1200 degrees and hold it right to the top of the tunnel. It takes about 5 minutes to get to the top, is this to long to run the engine at that exhaust temp?

 

[Ben Rumson]

You're OK

I've heard that Cummins tests these engines for extended periods of time at 1300.



1200 PT for the time you're talking shouldn't be a problem.



More important is to NOT shut it down right after you hit the top. Run through the top and down the other side - long enough for the air, coolant, oil temp, etc. to cool everything down (turbo, transmission, block). Re-stabilize your temps before shutting her down.

 

[Cooker]

I also wouldn't worry about extended periods of 1200 pre turbo.

 

[drees1]

1300 is where the Ductile Ni-resist material in the manifold begins to evaporate fast. That is how manifolds get thin. Also ours seem to creep and break outboard head studs as they shrink. 1200 all day long is OK. Just be sure your gage is right or know how to calculate it's offset. My westach gage references 70 deg at the junction, so if it is colder out it reads hotter than actual and if warmer out reads cooler than actual by the difference in the junction and 70. The junction is where the probe wires are connected up. In my case, under the hood by the brake booster. Other gages may have an electronic "ice point" and be dead accurate, always, just know what you got. Also keep in mind your manifold is divided so you are reading the front 3 or rear 3 cylinders depending on where you are tapping. There could be minor variations. The wastegate pulls from the rear only, does anyone know if it runs cooler than the front 3 in a pull? I guess most bombed trucks don't use much wastegate any way

 

[Roger rodbolt]

1200 is fine but......

If you head hasn't been ported number, one cylinder is definately running hotter then the "mix" that shown on the pyro.

 

[scaryfast]

I guess I knew 1300 degrees was the critical temp, that's why I use 1200 in case the gauge is off a little and to keep it below melt down. Doesn't aluminum melt at 1300 degrees? I am a little worried about the "number one cylinder being hotter" Roger, do you know how much hotter it runs than the rest?

Wastegate! We don't need no stinking wastegate!

 

[C Schomer]

There was a story in an old TDR. 1 & 6 ran about 100* hotter. The Twin Ram gets them within about 20* of each other. Cummins tested the B5. 9 at full load/1300* for 1000 continuous hrs. I guess that's about 50k miles on the average. I hold mine at 1250* on Eisenhower. Craig

 

[drees1]

Originally posted by scaryfast

Doesn't aluminum melt at 1300 degrees?

Crown temps on a one piece jet cooled diesel piston are probably not over 400 - 600 degF in the worst areas, where the bowl is re entrant or where the edge of the bowl is. It has been a while since I measured it. The boundry layer of air keeps the actual surface cooler, and it is only exposed to combustion temp momentarily, and to exhaust temp for a short time. When the exhaust valve opens and blows down, temps drop and most of the gas is already out before the piston pushes the rest out.



EGT will not melt pistons or be a direct indicator of their temp. Advanced timing is what will do it. It increases the time exposed at high temp, and the peak temp.

Originally posted by scaryfast



Wastegate! We don't need no stinking wastegate!

Heard that!!

 

[Diesel Freak]

Pure Aluminum will melt at 1220F



The pistons are forged Aluminum alloy... . melting temp is slightly higher than 1220F... but not much



While high EGT >1300F is possible on a gasoline engine... it is not advisable on a diesel.

 

[Roger rodbolt]

Oil cooled pistons

The pistons rely heavily on oil cooling from the oil spray from the rod big end. If the cooling nozzle plugs (ala' oil filter failure) the piston melts at normal operating temps. I've seen this on a stock school bus with a plugged nozzle... ... ... ... no flame intended but it did have the infamous F___ oil filter on it. The new Echo engines use an improved "swirl" oiling cooling to allow additonal HP. Larry

 

[scaryfast]

Thanks guys, I feel MUCH better.

 

[C Schomer]

Scaryfast, I got your PM and sent replies but I don't think they go thru - they don't show up in my 'sent' folder. I tow a 25' 5th wh 7400 lbs loaded. I go up to the tunnel from Dillon at 65mph, 4th gear, 1250egt, about 2600rpm and 26lbs boost. Water temp goes a little past center. What do you tow up there at 70? Craig

 

[scaryfast]

It's a 27 foot enclosed HaulMark trailer with snowmobiles, weighs about 5000 pounds. I come up in 5th gear, not sure on the RPM's, 1200 degrees, 70 mph, boost is 30.

 

[Darel]

The pistons rely heavily on oil cooling from the oil spray from the rod big end.

Does this mean if someone were to hypothetically put a windage tray on a Hummin' Cummins they would melt their pistons much more quickly than not?



Not sure why someone would want a windage tray on a diesel since it would redline before the tray made any difference, but I'm just speaking hypothetically.

Darel

 

[M Barnett]

EGT will not melt pistons or be a direct indicator of their temp. Advanced timing is what will do it. It increases the time exposed at high temp, and the peak temp.

I was going to advance my timing to about 15 but maybe now I wont.

Michael

 

[Ben Rumson]

Timing really HELPS !

Originally posted by M Barnett

I was going to advance my timing to about 15 but maybe now I wont.

Michael

As long as you don't advance it too much - it can help DRAMATICALLY !



I've gone to 15. 5 and the truck runs SOO much better. EGT's are not a problem.



I wouldn't go beyond 16 degrees for normal driving and towing. 16 isn't bad. Beyond this, pressures can get pretty high and the truck gets noticably louder (not that this is a bad thing), plus EGT's "might" come into play on long hard pulls.



By all means - advance your timing to at least 15. 5. Your truck will run MUCH better !!!! Advancing the timing was my very first bomb. Everything was secondary.

 

[Roger rodbolt]

Originally posted by Darel

Does this mean if someone were to hypothetically put a windage tray on a Hummin' Cummins they would melt their pistons much more quickly than not?



Not sure why someone would want a windage tray on a diesel since it would redline before the tray made any difference, but I'm just speaking hypothetically.

Darel

Darel,

Our Cummins do not use "splash" cooling for the pistons. I mislead you because the 5. 9 CTD uses cooling nozzles located in the main bearing journals in the block to spray oil on the bottom of the pistons. I believe that the crankshaft is positioned such that a windage tray is not needed (at normal rpm). In fact I've been told by Cummins that running our engines a quart overfull is not detrimental (no reason to overfill though). Larry



On the timing issue:



Increasing stock timing will reduce egt's but do increase cylinder pressure. That's why most knowledgable folks recommend 15 to 16 degrees. Race applications may demand a much different timing but also different boost levels, rpm, etc and longevity may not be a priority :{ :{.

 

[Mhannink]

Does this mean if someone were to hypothetically put a windage tray on a Hummin' Cummins they would melt their pistons much more quickly than not?



Not sure why someone would want a windage tray on a diesel since it would redline before the tray made any difference, but I'm just speaking hypothetically.

Darel

our engines as with all diesel that i know of the crank does not dip into the oil. gassers often do this but not diesels. thats why in gassers the windage trays are so popular. it takes a fair amount of power to push the crancks counter wieghts through the oil. a windage tray on any diesel isnt gonna affect the engine one way or the other. like rodbolt said our engines use a nozzle and directs oil pressure to the underside of the piston.