Need some diesel info

azmtnman · December 29, 2016, 09:45:19 PM

I go to pick up an '03 Dodge D2500 4x4 6sp with the Cummins in it tomorrow. It is the HO motor from that year plus the guy has put an aftermarket turbo, an external electric fuel pump and an exhaust brake. He says it should be about 400 hp. I believe it after test driving it!
My question is about the pyrometer. I have only driven one truck with a pyrometer and it had green, yellow and red range on it (fire truck) and I never saw it go above low yellow. This one is just numbers (I think x 100?) I know it is measuring exhaust temp. What should it run/not be above? What makes it go up too much. Do I have to watch temps using the exhaust brake?
I've driven lots of old school diesels.

ohiowoodchuck · December 29, 2016, 10:08:41 PM

Stay in the 1600-1800 range and you should be ok. Heat makes it go up but, heat is what is driving the turbo. You can actually melt the pistons down in one after a certain temp. Actually around 2200-2400 they start melting. You would hard pressed to get to that high of a temp even pulling a heavy load of a steep incline.

brendonv · December 29, 2016, 10:39:09 PM

It depends where its located too. Im told it should be in the exhaust manifold, not the down pipe. Do the research.

ohiowoodchuck · December 29, 2016, 10:41:42 PM

Correct, the exhaust manifold gives the most accurate reading. If it's in the pipe it could be 200-300 degrees off. So when you think your safe at 1600 your actually 1800 ish. That's with the probe mounted in the exhaust.

Gearbox · December 30, 2016, 10:40:30 AM

In the older big trucks we never ran them over 1200 . Look up the melting point of aluminum . The pistons have oil spray on the bottom and that lets them run some hotter . I just don't understand running high HP chips and shortening the engine life . The freightliner trucks running that engine are set at 170 to 210 HP pulling semi trailers . Enough rant from an old guy who ran Calif. with a 220 and hauled 6 Buicks .

Dave Shepard · December 30, 2016, 01:53:51 PM

1300 if before turbo, 900 if after. 1300 is the Cummins spec. Do not go higher!!!!!!!!!!!

mf40diesel · December 30, 2016, 02:05:40 PM

I have an 06' Cummins, in a 2500 megacab. Have a mild tune in it, with the factory turbo. (The holset turbo is pretty good) In my opinion if you sustain 1800 I believe you will be setting yourself up for some real problems. Granted I am no expert, just a diesel lover, but I am not even sure that the sled pulling trucks get theirs too far into the 2000 deg f range for more than a 30 sec pull. I believe if that was done even for a short time you would have a melt down. My pyrometer thermocouple is placed in the manifold, where it should be hotter than post-turbo, going down the highway at 70 I see ~700-800 deg, pulling my hill, in a locking gear I can just get it to the 1200 deg mark, but I don't hold it there long.

I guess, my advice, and it is just that, but I would lurk around on some purely diesel enthusiast sites before you push the temp too hard, even though it is a cummins. Even they are not indestructable.

Just my .02

s grinder · December 30, 2016, 03:49:51 PM

1250 degrees would be a good red line for that motor,if your pulling weight up a grade you'll notice the temperature will climb if engine starts to lug.Down shift and once you get the revs up[turbo spools up]temp should drop,if it still climbs,back off the throttle.If it has a tow chip/programer,you should be safe,if it has a high output chip/programer you won't be able to tow anything.That 1600/1800 temps might be good for sled pulling,short bursts, but not for towing.I personally wouldn't buy a truck with a modified diesel unless i knew the owner /mechanic who did the mods.

ohiowoodchuck · December 30, 2016, 04:34:26 PM

They won't start melting till 2400 they run there best at 2200. I hit 1500-1800 on my bone stock 96 3500 all the time. When I pulled the head at 210,000 the pistons were good as new. My dually spends more time with a trailer then it does unhooked. Just giving my experience but to each there own.

Dave Shepard · December 30, 2016, 07:02:42 PM

You can't hit 1500 on a stock truck. Your gauge is junk. Google "melting point of aluminum".

ohiowoodchuck · December 30, 2016, 08:46:09 PM

I've put two different exhaust temp gauges in it both cost close to 200.00 one was a isspro and the other was a Stewart warner. Both have the same reading. Pistons are not just aluminum they have a alloy mixture to withstand the heat and stress from combustion. I regularly ran a 5.9 Cummins at 2200 degrees and seen no failure. At 2400 degrees they start showing signs of fatigue and heat cracks at 2600 they will melt and seize in the bore. All temps were recorded with a corsa data logger. I ran 3 seasons and 60 passes with the temp constantly at 2200-2400. The next season I ran it at 2600 and it lived for 6 passes and it seized at the end of the track. I tore motor apart at end of every season and inspected and installed new bearings. In my opinion hitting 1600 going up a hill pulling a trailer isn't going to hurt nothing. I respect your opinion hope you respect mine.

Dave Shepard · December 30, 2016, 09:43:02 PM

I do respect your opinion, but you are not talking about the same situation as the post I was replying to. You said you were hitting 1500-1800 on a bone stock 12 valve. Not going to happen. Running 2000 plus for the duration of a pull is not the same thing as pulling continuously on the road. The safe pyrometer reading, pre-turbo, is 1300F, and that is from a Cummins engineer that worked on the B series engines.

ohiowoodchuck · December 30, 2016, 10:24:43 PM

Yes bone stock trailer weighs 5700 skidsteer 10,900 going up a steep long hill on the highway. 5th gear 4.10 ratio 2200 rpms. Does it everytime. You didn't ask for a apples to apples comparison. I was just telling you at what my experience was at when a piston will melt. I use to pull trucks with a guy who worked for Cummins. He had over 300,000 miles and 300 passes on a stock bottom end including pistons. He ran it from 4800-5500 rpms and regularly over 2200 degrees and it lived a long time. I would worry more about a injector sticking and washing out a cylinder on a common rail Cummins before I would worry about heat melting a piston. Another factor to look at is the temp you see on the gauge isn't the temp at the piston. Heat is energy in a diesel, the combustion chamber is surrounded by water jackets the same as water flowing through the cylinder head. When the intake valve opens in pulls in a colder charge of air that also acts as a cooling effect to the piston. The temp you see at the gauge is the end result of the combustion so it would be the hottest temp only seeing the piston for a very short time that builds in the manifold. If you increase timing on a diesel you will in fact reduce the time of the cooling effect from the air and increase your cylinder pressure.

danbuendgen · December 31, 2016, 05:54:20 AM

New to Dodge Cummins trucks?? Try http://www.cumminsforum.com/forum/3rd-gen-dodge-cummins-03-07-common-rail-forums/

My .02 on EGTs on a 5.9 is don't worry about EGTs unless you have a aggressive tune and are hammering down for excessive periods, or pulling heavy heavy trailers up steep grades. I have had 4 (89, 95, 03, 08) Dodge Cummins trucks over the years, 3 of them have been turned up and I have never seen high enough EGTs to worry about it. I don't even pay attention to the gauge anymore.

I will say for a 03 get a fuel pressure gauge and a rail pressure gauge and a good fuel filter set up (http://www.dieselfuelfilterkits.com/cummins_fuel_filter_kit.html) and drain your water separator on a regular basis. Good filters will keep your injectors around for a long time and injectors are not cheap on these trucks.....

GOOD LUCK with the new truck and have fun with it.