I'm sure there's something I'm not realizing here so I'm gonna ask...I was looking at some pics in a few of your galleries and I noticed that alot of your pyro probs are drilled in the top of the exhaust manifold. The thing I thought odd was it is usually in one side or the other and not in the middle. Am I overthinking it to think that if it was in the center of the manifold that gases from all cylinders would pass the probe giving a more accurate reading? LCH

 

Not too sure about the common rail trucks, but the older manifolds actually have a divider plate right down the middle, so you can't drill and tap near the center.

g

 

and the hot ones near the rear are what ya wanna watch, cyl. #'s 4 5 6 run hotter so watchin the hot ones will make sure all are ok.

 

5 and 6 actually run hotter than 1,2,3, and 4 because they're at the end of the rail.

 

Ask cummins directly, and they will tell you put it behind the turbo.
In the early days Cummins actually put them in the manifold, and that they made the change to behind to turbo, for some unknown reason, and its been that way ever since. My company is a cummins Dealer, and that came directly from the tech from the local distributor.

 

So does the air cool any when it's pulled thru the turbo or would you get the same reading as having it in the manifold?

 

I have been told that there is about a 250-300 degree difference between pre, and post turbo.
In my opinion I prefer post turbo, and keep her at or below 1200 degrees.
I have seen the effects of a pre turbo thermocouple when they get a few years on them, break off, and go through a turbo, (not pretty).
I personally don't think pre turbo is not worth the risk, I know alot of guys do it, and that it doesn't hurt a thing in their opinion, but it is not my prefered way, as I said, working in a shop, I have seen what can happen.
If you look in an isspro parts book, you will see that they do offer a pre turbo pyrometer, and a post turbo pyrometer choice, it basically shows 3 zones green, yellow, and red, the difference between the two is where the zones are placed in relation the the temp difference between the two.
Hope this helps, I don't wanna get another pre/post turbo war going, this is just my 2 cents.

 

Yes, that all makes sense. I hadn't given any thought to the pre/post placement until your post. Did they give you any temp range to not exceed if placed post? All of this is new to me and I want to educate myself as much as I can before I do anything to my truck. Thanks..LCH

 

True of 3rd Gens also. Drill between rear and center.

 

Is there a projected lifespan of the thermocouples? I never even thought about it rotting out or breaking off one day and causing me to have to buy a bigger turbo or twins.. Oops, did I just say that????

 

I've been reading this site for a long time.Been reading TDR almost from day one.Have NEVER seen a post about a egt probe failing.Theres a lot of 1st & 2nd generation guys that have had same trucks for a LONG time.Lots of posts about things failing but never a probe.I just installed a Westach boost/egt combo gauge and never considered post turbo.My third truck and all of them I did pre turbo.

 

Me neither.....