Pyro probe probs pre-turbo?

[Darel]

I was gabbing with my local Cummins guy and he said you shouldn't mount your pyro probe pre-turbo. Yes, it gives you more accurate results, but he said the tip gets too hot and melts/breaks off, thus destroying your turbo. To make his point he pulled one out of a drawer, and sure enough the last 1/4" of the probe was gone. Anyone ever heard of this happening? I'll probably switch mine back to the post-turbo hole it was in just to be safe.

Darel

 

[Whitmore]

Darrel, IMHO if you get that hot than you have damaged alot more than your turbo, chances are you will also melt some pistons too,I cant remember what it is but the pyro tip is good for alot of heat. someone did a big test on pyros in the mag not to long ago and the results were very interesting... ... ... ... ... ... ... Kevin

 

[Deezul1]

The whole point of a pre turbo install is to read the EGT sooner and quit making it so hot that anything will get damaged. If its hot enough to melt the probe the engine has big trouble and somebody wasnt watching the gauge. I believe turbo aircraft have the probe pre turbo so it cant be a big problem.

 

[Bigsaint]

IMHO, keep it where you have it !!! We have pretty much beaten this issue to death. I don't recall one member losing a turbo to a egt probe.



Scott W.

 

[EMDDIESEL]

With all the months gone by since i have been gone, this question still arises. Go pre turbo, like everybody has said, if your EGT's are hot enough to melt a Thermocouple, you have more serious problems. And even if it did get hot enough to melt the Thermocouple, the turbo blades would melt too.

 

[Darel]

Can someone point me to a thread where you guys have discussed this already? I did a search but came up blank.

 

[Dennis Garrett]

I've got 5 years & 153k on my Combo gauge, no problems except one. After reading all the posts about pre-turbo mounting, I removed my thermocouple a couple of times to inspect it, & broke a wire. Each time it was fine, but had to order a new one. My advice would be to put it pre-turbo, don't worry about it, & don't ever remove it. One thing to consider, when locating the hole, don't drill dead center, there is a rib cast inside you won't get through, drill left or right of center.

 

[THerman]

As has already been stated, stick with pre-turbo... .



To reach temps high enough to melt that T-couple your rig would just about have to be on fire! and even then the thermocouple would probably survive inside the manifold!



I design sensing and control systems... . and there is almost no way you are going to melt the thermocouples that come with the egt gauges.



Tod

 

[CJ Johansson]

Melting temp of thermocouples

Most of your thermocouples are made with a stainless steel casing over the actual thermocouple. The actual sensing unit is just a junction in two different types of metal wires, which is enclosed in the stainless casing.



Most stainless steels melt in the range of 4600*F to 5050*F, which is just a tad over the safe range for EGT in a diesel engine



Even if the casing were made from plain mild steel, it wouldn't melt (it might corrode/erode from the hot gasses) as mild steels melt in the range of 2500*F to 2700*F.



Bottom line is, you just ain't gonna melt a thermocouple probe...



-cj

 

[dresslered]

I'm a post-turbo guy, but my goal is different than most of you.



http://dieselram.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=000105

 

[Royal]

Darel---I would not let your Cummins guy on my truck. I have worked on jet engines and diesel engines for over 50 years and have never seen a melted pyro probe. He must have used a cuting torch on the one you saw.

 

[C Schomer]

The old timers used to tell me about melted TCs when I had OTR trucks but I never saw one either. I pull mine out about yearly and make sure it looks good. After 4 yrs, it looks like new except for that black stuff! Craig

 

[shendren]

why would anyone want to read egt's past the turbo? the turbo adds energy with the compressor stage and thus the temp goes up again? thus the intercooler.....

 

[RustyJC]

Originally posted by shendren

Why would anyone want to read egt's past the turbo?

The engines our company builds have t'couples in each cylinder's exhaust elbow as well as one before each turbo. The only time we care about exhaust temps after the turbo is if (1. ) we are mapping turbocharger performance or (2. ) the exhaust is going into a catalytic converter, waste heat boiler or other temperature critical equipment.



Rusty