I am looking for thoughts/suggestions on this topic. I already read as much as possible on the search function, not much post turbo stuff.

I know two things:

1. The general concensus on FTE is pre-turbo, left rear manifold placement
2. The manufacturers; autometer, International, Ford, Cummins, and our Cat equipment techs all say post turbo

The Caterpillar and Autometer people said it is safer for the turbo if the probe were to break and/or all metal shavings had not been removed to go post turbo. This makes sense.

It also makes sense to go into the manifold to recieve instantaneous, highest recordable tempatures for the exhaust.

I will finish the installation this week and would like to get this issue resolved.

Can I get help from you guys on pre/post turbo EGT differences?
What temp is safe to not coke the turbo w/ a post turbo pyro?

I have no modifications yet so I am confident high temps won't be a problem...but, I can always plan for problems in the future!

 

This can be a BIG controversy even here among these nice folks...

The post turbo location ensures that a failure in the probe will not hurt the turbo... That's why the probe manufacturers suggest that - to limit their "exposure" ...

BUT the post turbo readings are slower to react than the pre-turbo since they are closer to the "firing" location... Some say as much as or more than 400 degree lower readings on post turbo locations... so if 1250 pre-turbo is bad for the aluminum fins in the turbo, than 800 post turbo is approaching the danger point... IMHO

In the real world, I've never heard of a pre-turbo probe breaking if properly installed...

but, it's your truck and your decision

 

What he said . . . .

There was a pretty good post once by a user who had probes both pre and post turbo and he had interesting comments on the temperature differential between the two. It was not a static differential and was highly dependant on load and operating conditions.

I was all set to go post turbo but after looking at the probe when I got the kit decided what the heck and went pre turbo. The probes are pretty stout and have a much higher melting point than they'll ever see in a PSD application - a lot of other stuff will melt first.

 

EXactly, the turbo, valves, pistons, etc. will all be melted before a high quality pyro probe is damaged enough to disintegrate and get pounded through the turbo. If you damage it before installation however, like dropping it, you are definitely stacking the deck against yourself. Just be careful and get the shavings out by finishing your drilling and tapping with the engine idling so that the exhaust pressure blows out the shavings and you'll be fine there. I have worked on diesels for most of my life that I can remember and I have never actually met anyone who has even seen an engine that a pyro tip broke off and caused damage in. I have seen one that was installed in a 6-71 detroit that when removed had some small chips in the probe and it was pre-turbo and the turbo showed no damage. The engine was in a skidder and ran at governor all day every day and there's no telling how many hours were on the engine and how hot it had gotten over the years. By small chips, I mean smaller than a pencil lead shaving, not chunks missing or anything. Also, the engine was still running great when it was torn down, but was rebuilt due to excessive oil consumption, and the pyro was checked simply because the turbo inlet tube was off and we were checking everything. Hope this helps with your decision. Oh, by the way, Autometer makes great gauges, but every manufacturer buys their pyro tips, all different makers, but they stick with quality or they would have too many people complaining and would lose too much business, especially since so many people do install pre-turbo. Mat

 

Well said

 

Coming from you, that's quite the compliment, thank you.

 

I've ran both pre and post turbo with the thermocouple on my 7.3 PSD.

Post turbo hardly ever moved while driving, when it did move it would do so very slowly, and it never got above 900*.....rarely got above 800*.

Pre turbo reacts much more quickly, and goes over a broader temp. range while driving 400-1300*+.

Under idling conditions they would measure the same eventually, cruising with no load would be similar. Big difference it temps acclerating especially under WOT.

There really isn't a set difference between the two, so determining a safe max temp would be hard to do IMO.

From what I remember the thermocouples are rated to 2300* (or somewhere close to it).

$.02

 

Can't say as I've ever heard of a pre-turbo probe breaking either. All of mine have been pre-turbo - no problems...

 

My probe has 120,000 miles on it from 2 different trucks and it looked brand new when I removed it to put it in my new truck. I would never worry about it having a problem pre turbo.

 

I have both pre-post....just for your info they both change and read togeather. No delay in post from pre turbo....might be nano seconds if it is.

My pre turbo is in the left ex manifold, and post is 4 inches from the turbo outlet.

 

Out of curiosity...what is the temp difference on your truck?

 

On average about 250 less post turbo

 

...so there is a variance? If so how much...and are the changes more prevalent under certain conditions? I am assuming its not 250 all the time...

 

Guess what I am saying is that when I have a temp increase, both gauges move, not the pre then post. I never have high temps with the exhaust upgrade and most times it runs on average 250 degrees apart. If you could log the temps you might get a better idea.

 

That's what I was looking for. I will try to talk my CAT buddy (mechanical engr) into the pre turbo mount but if I go post I guess I will have the info I need