Engine/Transmission (1994 - 1998) Thermocouple installation in manifold

[PMerrill]

I understand the reasoning behind installing the thermocouple in the exhaust manifold, but have heard horror stories of tip of thermocouple falling off and destroying turbo vanes in hot housing side. I previously have worked as a heavy truck technician for Peterbilt motor company and noticed that every engine manufacture including Cummins installs their thermocouples post turbo. I am installing a Banks Git Kit on my 1996 Ram 3500 4x4 and want to make the best decision on where to install the thermocouple on my engine. Just wanted to bring this up and see what kind of response it brings up.



Thanks in advance for responding it will help largely with my decision on installing thermocouple on my engine. I highly regard and admire the technical advice that all TDR members give.

 

[kenny61]

Most here will tell you installimg it post turbo is userless as you are just guessing what the pre temp is. I have read about some failures but they seem rare. mine has been pre turbo for 3 years with no problems(knock on wood) it is an autometer

 

[BigPapa]

What's up Paul?! Welcome to the TDR.



Mines in the manifold. In all my years of membership here, reading other forums, and talking to diesel owners, I have never heard of anybody that actually had this happen to them. I've heard the stories, too, but can't get anybody to tell me it's happened to them.



I'd do it again and I'll be glad to help you with yours. I have an 1/8" tap if you need it.



Scott

 

[BigPapa]

Forgot to mention, come on over here:



https://www.turbodieselregister.com/forums/southeast/84233-mid-tenn-chapter-roundtable-135.html



and introduce yourself. That's where all us Mid-Tenn boys hang out.



Scott

 

[SRadke]

I've never heard of a thermocouple related turbo failure and I always install them pre turbo. Of course I would advise against the Banks kit too so take it as you will.

-Scott

 

[PMerrill]

What is it about Banks kits you do not like?

 

[FFL8N]

The cost associated with the name..... too much advertising costs involved. .

 

[SRadke]

You can do better for the same money. I also dislike how everything (gauges included) are routed through their box so when any component fails you're forced back to their components or to start completely over.

-Scott

 

[CumminsPower98]

Manifold for me with hundreds of thousands of miles and lots of towing and high temps. I don't remember reading of a failure on here. Oh and I have Auto Meter with their higher end probe in the manifold and the one that came with the gauge after the turbo.

 

[Forrest Nearing]

the FAA approves pre-turbo thermocouple installations... if it's good enough for an airplane, it's good enough for a truck that you can pull off the road



your pistons will turn to molten aluminum before you'll melt the thermocouple

 

[BDaugherty]

You can do better for the same money. I also dislike how everything (gauges included) are routed through their box so when any component fails you're forced back to their components or to start completely over.



-Scott

Interesting perspective, sir. I'm not promoting Banks or knocking it either. However I always liked how everything was routed through the box so that you had minimal wiring. Also, that way you get a gauge and EGT limiting with only one thermocouple. However, I certainly see your point.



Also, I would put the thermocouple preturbo and it wouldn't bother me the little bit.

 

[Geno's Garage]

We have heard the "stories" too. Personally, I have been with Geno's Garage, selling EGT gauges, for 7-1/2 years, and have heard that concern dozens of times. I have yet to hear it from someone who has actually had it happen to him! We have sold, literally, thousands of EGT gauges and have NEVER had a single thermocouple break, and do other damage.



As far as pre- or post-turbo mount of the thermocouple, do what makes you feel most comfortable. Some will tell you that post-turbo mount is inaccurate, or unuseable. That is a misunderstanding of what the gauge is telling you. The turbo uses heat energy, so post-turbo temperatures will be lower than pre-turbo temperatures. Post-turbo mounted thermocouples will give an accurate reading of post-turbo temperatures. Someone previously suggested that with a post-turbo mounted thermocouple you are only guessing at the pre-turbo temprature. That is correct. If you want to know what the pre-turbo temperature is, install the thermocouple pre-turbo, in the exhaust manifold.



Regardless of where you mount the thermocouple, you will be reading temperatures across a wide range. The purpose for monitoring these temperatures is to watch for "heating trends" (watch for temperatures higher, or lower, than you normally experience under similar conditions). Don't let others scare you into thinking that EGTs above 1250 will melt the aluminum in the engine. If that were the case, VERY few of the Dodge/Cummins trucks would be on the road today (aluminum actually melts at around 1220 degrees). Remember that you are reading AIR that is being rapidly compressed, and super-heated through compression. You are not reading the temperature of the engine's aluminum components. Try keeping the EGTs below temperatures high enough to reduce the service life of engine/exhaust components, around 1250-1350 (pre-turbo), or 1000-1100 (post-turbo). These temperatures will be easy to stay below on a stock truck, with no load. Start adding performance fueling components, heavy loads, and/or very hot outside air temperatures, and you will approach, or exceed these temperatures easily, but with an EGT gauge, you will know when you have reached these temperatures, and can take steps to reduce them.



The debate between pre- vs. post-turbo installation is as alive and strong as the Coke vs. Pepsi debate. Install the thermocouple where you want, and drink the cola of your choice.



Geno's garage suggests mounting pre-turbo for monitoring of the hottest temperatures in the exhaust system, and ease of access to your installation point.



Hope this helps.



~Andy

 

[Forrest Nearing]

Andy, great post...



while it certainly won't hurt to keep temps below 1250*, I always say, put the pyro on a stock truck and go haul a big trailer at high altitudes!



the size of the piston allows it to dissipate heat, especially when combined with the cooling nozzles bathing the undersides of them with oil

 

[gitchesum]

I've registered EGT's over 2000* in my truck with 5 different thermocouples installed in it and not a one showed any sign of damage.

Also, to back up Andy's statement, when I pulled my head due to a dropped valve seat, there was absolutely no damage to the piston whatsoever. You could still read the number printed on the top.

 

[kenny61]

Was probably real clean after 2000*:-laf



I've hit at least 1600* don't know for how long, when i wasnt paying attention. Looked over at the EGT gauge and it was buried

 

[gitchesum]

Pretty clean.

#ad

 

[Shadrach]

I have been in the heavy truck/diesel industry for over 25 years and Yes all the OEM's mount the pyro post turbo and Yes all the older mechanics will tell you Not to mount it pre turbo. Have I ever personally seen a tip damage a turbo? NO. With the technology of todays materials I will not be afraid to mount mine pre turbo. I have seen One tip burn off, but he was pushing over 800hp and 100 # of boost and it burned a hole in the tip but didn't do any damage to either of his turbos. ( He broke lots of parts on that 12 valve over the years. ) Isspro, for example, makes a tip that is good for over 2000*. The main thing is know your range and drive accordingly. Shadrach

 

[CTD12V]

Ditto on the Isspro tip. My Isspro gauge package came with the hi-temp Inconel thermocouple which is rated for 2000* F.

 

[Pliska]

As mentioned above, the ISSPRO high-temp Inconel thermocouples are rated for sustained 2000°F.



I have checked around here at ISSPRO, and we do not have a single recorded instance of a tip burning or breaking off of a modern thermocouple (the type we have been building for over 20 years). The tip damage incidents I have heard of involved old style thermocouples, in which the welded thermocouple wire junction was exposed directly to the exhaust. Modern automotive thermocouples encase that junction in a metal housing, to give it mechanical strength as well as heat resistance.



On my truck I have been running pre- and post-turbo pyrometers for a while, and seen them in a variety of conditions. The temperature differential can be anything from "-100°F" (where the post-turbo location is 100° warmer), to +500°F under a heavy load. Given that range of differential, I would never rely solely on a post-turbo installation, at least for my truck.



Regards,

Michael Pliska

 

[Shadrach]

Hey Pliska I just got my EV2s. Nice gauges. Waiting for the tach to be available. Shadrach