Pre-Turbo EGT Gauge Install

[rbattelle]

Has anyone successfully installed a pre-turbo EGT gauge yet? If so, where and how, exactly? I thought I remembered someone did it, but for the life of me I can't find the post.

 

[amsoilman]

I have a Friend who has the new 03' HO engine, and he mounted his pyro thermocouple in the manifold, just above the turbo flange on the front three cylinders. It's mounted on the side of the manifold. He drilled and tapped for the thermocouple.







Wayne

amsoilman

 

[bzingre]

Pre-Turbo

I understand the fact that all of you guys with Pre-Turbo Pyros are trying to get an accurate reading of what's going on at the manifold. But is that it? It seems to me that a better idea is to put that thing as close as you can post turbo. There are so many chances to destroy that turbo that it seems real risky. Not to be a traitor or to blow my own horn, but at work (Caterpillar Truck Engine Division), we don't advise or deny the use of a pyro on our engines, but we do say that an appropriate place to install them is post-turbo 18". The advantages of post-turbo installation are: one, the thermocouple stays cooler, thus last longer, two, if the thermocouple fails, it won't go through the turbo, three, there are no holes in the exhaust manifold that would create stress risers and lead to future cracking due to repeated thermo cycles, four, any chips left over in the manifold after the hole is drilled won't go through the turbo if the hole is in the pipe. There might be more advantages that I'm not thinking of, but I no for sure that any chance to cause forgein material to pass through the turbo is like making a deal with the devil.

 

[Brett Maverick]

A'men!!!

I dig your train of thought.

A little math will provide an accurate set of operating paramaters for "post turbo" operation, and a whole world of security for that turbo. Not to mention, that the exhaust brakes usualy come with a threaded port for the thermocouple, so you don't even have to drill a hole.



If I put gauges in my '03, I'll fer-sure dangle the heat seeker "Post Turbo".



Brett.

 

[Mark_Kendrick]

Every different turbo has a different thermal chage across the turbo. the HY vs HX35,40, vs different housings, exhaust manifolds, piping etc all have a d9fferent change in temperature from before the turbo to after it. So, how could post turbo tell you what is going on inside the engine.



the purpose is to see what the temp is of the exhaust gasses coming out of the engine not tell how hot the turbo is right now.



Ideally you need both. one to tell a bout the engine the other to tell about the turbo.



FWIW,

Mark

 

[rbattelle]

I hadn't thought about the possibility of the thermocouple breaking... remote, but possible.



For some reason, the pre-turbo installation seems safer to me, since you are directly monitoring the engine. With post-turbo, any information about how the engine is functioning is buffered by the turbo. Temperature change across the turbo will change depending on boost pressure, flow rate, etc.



By all means, I would prefer to install one post-turbo (if you garf up the install it's MUCH cheaper to replace the turbo downpipe than the exhaust manifold). Ideally, you'd install one pre and one post and monitor both.



Where do most people install it and why? I had been under the assumption that most people installed one pre-turbo. If Caterpillar advises post-turbo, maybe that's the way to go. What does Cummins think?

 

[amsoilman]

On my 94', I had the temp probe located "post" turbo for a good share of the time I owned it. The probe was located in the elbow of the BD exhaust brake. I switched to the "Pre" turbo location for the probe by drilling and tapping to accept the probe. All I can say is; there is a BIG difference in the readings between the two locations. First off, the gauge reads very fast in the Pre turbo location, and is as much as 350 F different at various times. This was observed pulling identical loads up the same hills The big thing is the response with the pre turbo location... ... ... ... ..... very responsive!

As too the liklihood of having the probe brake, I think it would be very unlikely, as I have never heard of one braking in all the years I've been associated with the Dodge/Cummins applications. First one was a 91 CTD.





Wayne

amsoilman

 

[MLee]

pyro

the pictures that was posted couple weeks ago on the "03" that was put on the dyno that had the new hardware on it, was post tubo. it did'nt look like there was a good spot in the manifold to mount 0ne. just my penny's worth.



Marv.

 

[RSnaith]

Good post on the pre-turbo install reasons, and indeed most heavy equipment manufacturers place thermocouples post turbo. However this is because they are operating within a given set of often fixed parameters, such as max turbo boost.



So here's a few reasons for pre-turbo install





1) in light/medium duty trucks, the importance of measuring turbo heat is less than the importance of watching cylinder temps. The turbocharger is capable of handling more heat than the pistons/cylinder head/exhaust manifold, and except at deceleration, the post-turbo temps are never higher than pre-turbo temps.



2) Parameters are no longer set in stone, especially boost and load, so simple mathematics doesn't give you a realistic measure of exhaust gas temps. For example, cylinder temps can be off by as much as 350F, due to changing boost levels and outside air temp. Heavy equipment is rarely ever more than 200F different between pre and post turbo, and when under load, boost levels are often at a constant, so there isn't much in the way of math to worry about.



3) The chance of a thermocouple breaking is virtually nil. Murphy is alive and well, but having put millions of miles on heavy trucks, and more hours than I care to think about on old field tractors, I have yet to see a thermocouple break, pre or post turbo. They're manufactured to read up to 2000F, and have about 30% tolerance built in.



Rod

 

[DIESELMAN]

Boy this subject has sure been covered a lot!



I've got ONE reason for POST turbo, its spelled I-M-P-A-T-I-E-N-T , I wanted to get mine in but didn't have el deseo to pull the manifold.



Not worried about chips, just couldn't find the right angle drill to squeeze in there!



Besides, the post (elbow) drilled hole will go away when the brake gets here, eventually, and the truck will be dirty by then, it wont bother me to get in there and make some slivers!Oo.

 

[FourBarR]

pre or post ?

i have a 98. 5 and installed mine pre turbo. all the aircraft i have worked on in the last 22 years have the thermocouple pre turbo and the max egt is 1650 f. i have never seen a probe break off. if its good enough for continental and lycoming , its good enough for cummins. my 02 cents. Oo. Oo.