Hey just wondering if this is a good spot on the downpipe to put an EGT probe. The previous owner put it there but I thought maybe it was a bit too far down the exhaust pipe. Going up a 6% grade with an empty truck, crusing at 65 mph and boosting about 10 psi, EGT stays around 625 degrees F. Does that seem about right for a post turbo EGT?

 

Here ya go..............

Mine is a 24v. Most everyone agrees the probe should be "pre" turbo.

 

Low but not too far down. As CR said, and you have probably read, pre-turbo is highly recommended for easier recognition of dangerous temps.

Post turbo is better than no probe...but be sure to add 500* to the reading, when under any load.
Ignore anyone who tells you adding 300* is enough. Especially if you add HP.

In other words, I would stay at or under 700*-750* under sustained "work".

RJ

 

Ignore anyone who tells you adding 300* is enough.

Yes ignore that certified cummins diesel techs say to put the probe post turbo, as close to the turbo as possible and add 200-300 degrees to you reading.

 

It's hard to argue with a certified Cummins tech. Unfortunately, there is a gazillion of them out there, and not all of them graduated top of their class. Plus, in wcbcruzer's case, the probe is so far back you'd think it was an O2 sensor sitting back near the transmission.

 

Crobtex has the probe in the right spot....installing the probe anywhere else will not be a substitute for this location. I would not accept any other pyro probe location as being accurate. Is it worth melting a piston?

 

I ran a pre/post combo for a while and finally just ended up with the pre because they were both pretty much equal until you stood on it. At that point I saw as much as a 500* difference between the two. And that's when I was stock. The only thing a post turbo EGT is good for is cool down. Other than that, I wouldn't listen to it. Especially when pulling a trailer up a 6% grade.

 

I've got a 12V. Put mine in last night, same location. I've seen 2 different measurements. One says go 2" from the flange where the turbo/manifold meet, and the other says to go back 3/4" from where the flange drops down to the flat part of the manifold (By back, I mean towards the engine). The other measurement is 5/8" to the rear of the truck from the center line of the manifold (There is a divider in there).

Get a tub of bearing grease. What I did when I was tapping, I dipped the tap into the grease, up to ~3/4" or so. That way when you're cutting the threads, all the slivers & shavings get stuck in the grease. I just wiped out the grease and dipped it again for each time I cut. Seems to have worked out pretty good.

Here's mine:

 

I'm at work and the pic is blocked, can't see it. But I did mention to mount it as close to the turbo as possible. There are a gazillion certified cummins techs, but the ones I talk to have around 30+ years experience working on more than just cummins diesel engines. In the end, its your truck and your money, put it where you like.

 

This is what I was led to believe is the "correct" location. Note how far the probe protrudes into the manifold-- not as far as you may think.

 

That's why I don't understand the recommendation by a Cummins tech that post turbo is a good thing. 950 post-turbo could actually be 1450 degrees pre-turbo. It sounds like the Cummins techs are more worried about the tip of the probe breaking off and destroying the turbo and possibly feeding the engine with turbo parts than they are about the pistons getting too hot. Perhaps the 1250 degree number is more of a guideline. I wonder how long one could pull a grade at 1450 degrees before anything bad were to happen?

 

You put it much kinder than I would have.
I've known two guys who have melted down pistons following the add 300° to a post turbo reading. 500° is more like it. Better yet go pre-turbo.
Most Cummins techs work on stock engines, especially on the big rigs, where a meltdown is more difficult and egts don't all the sudden skyrocket like they do on a modified engine.

 

Depends on the truck. On 1st gen, probably a second or two. On a second gen, a little longer. On an early 3rd gen, longer still. With an 04.5 or newer, probably close to indefinitely.

 

The other reason that post-pyro reading are MUCH more variable on our trucks than on big rigs is that they have proportionally larger turbine housings They don't need to have super-duper spoolup, instead they need to be able to sustain a long hard pull.

Your DODGE, otoh, has a really tight turbine side designed to help spoolup, so it causes drivepressures to easily skyrocket, and take pre-trubo EGT along with it.... This won't show up post turbo because of the huge pressure drop across the turbo.

If you had a huge turbine housing on your truck, like an 18.5 or a 21 housing, then a post-turbo pyro would be fine, imo. Even then, you should limit this config to 350hp or so.

People make a lot of mistakes in thinking that "what's good for a big rig is good for me." Your truck isn't a big rig. It isn't designed exclusively for towing-- there are concessions made for driveability when empty. (not to mention you have a lot fewer gears on your Dodge, so you need faster spoolup to pull wider gear splits).

jmo

 

Mine is post turbo, but I have wanted to go Pre turbo for a while. Hopefully I'll get it done soon.

Mike