Post Turbo Probe Install

[Jayhawker]

I know most members favor pre-turbo installation. However, I am considering installing post-turbo with the probe fairly high on the stainless steel turbo drop pipe. A hole would be drilled on the passenger side front corner (just outside heat shield). The probe fitting would be welded by a professional welder using ss rod. This would be done in-place.
I would prefer this location because I believe it is as close to outlet side of the turbo as you can get. Would drilling and welding this drop pipe have much potential for future cracking because of the high thermal expantion and contraction? Any comments on installing at this location (other than pre versus post turbo)?

[BassinRVer]

To my knowledge no manifold has crack because the probe was put in pre turbo.

[chuntag95]

Most of the fittings that have been tapped into manifolds have been brass. It will deform long before the cast iron cracks. Welded ones should be fine as well. The probability is not very high for cracking pre turbo IMO.

[ibelyea]

I was leary of drilling the cast iron preturbo, but was convinced by many on TDP that it was a piece of cake. After reading Hoot's discription and pictures, I found it was a snap and the probe was installed in less than 20 minutes. Easy to get to, easy to drill and easy to route. My previous probe was in the downpipe of my 98 6.5. This one responds better, gives me good steady readings and I know what temps are being pushed into the turbo. I just finished a 6500 mile trip and kept the temps below 1200 even in the mountains. I think you would have to wonder if the temps going into the turbo are safe if it were sensed post turbo. You know for a fact that they are correct with the preturbo (depending on the accuracy of the probe).

[svpdiesel]

I believe it is a bad idea to weld on anything while it is attached to the engine due to all the electronics it has. Even if you run a separate ground, the current spikes will probably kill something expensive. :eek: If you really want to weld, take the downpipe off the truck. Or, get a better temp reading and put it in the manifold pre-turbo. No welding... smile.gif

[GM Smitty]

Jayhawker - Check this thread out I started awhile ago:
Pre-Turbo EGT Installed (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=3;t=006022#000000)

I have my post-turbo EGT probe where you are talking about (high on the downpipe, close to the turbo). After installing my pre-turbo gauge, I couldn't believe the difference in temps sometimes. Something to think about....

Josh

[Jayhawker]

Josh - Thanks

I have been going back and forth between pre and post turbo. My gut feeling is the "instantaneous" pre-turbo reading is somewhat akin to the instantaneous mpg reading on my new 2003 . . . I almost wish it wasn't there because I find myself staring at it so often.

I don't push my truck with high settings on a performance box. When towing with the Juice in Level 1 on my 2001 2500HD, which had a post-turbo installation in turbo down pipe, I would force a downshift if the EGT got above 1100. This would only occur on long, steep mountain grades. But since you (and others) state the pre/post readings will differ by more than 100-200 degrees, maybe pre-turbo really is better.