Best place for EGT probe?

[AH64ID]

This was not mentioned, When post tubo installed you have to keep in mind a temp difference of approximately 300* cooler than pre tubo. The cooler temp looks cool but you don't want the piston to get above the 1250* and get damaged. A lot of PRO & CON. OTR trucks have them post. They are working harder than ours. And the 5-6 area is your hottest spot.

It was mentioned, and the small housings on the HE341 and HE351 make for a less predictable variance, so 300° doesn't always work. On older, or aftermarket turbos that have properly sized turbines then 300° guess is better, but still not accurate.

Even pre turbo has it's flaws, as timing plays a huge role in EGTs. 1450° might be fine on a 2005, but might melt a 2003.

 

[cerberusiam]

Zombie thread arises. :-laf:-laf

Funny how some objects of discussion transcend time and space.

 

[AEdelheit]

One thing to keep in mind on all the engines that come with post turbo EGT probes is that it was engineered using post turbo reading so the engineers now what the egts need to be post turbo to within specs. We dont have that knowledge, Pre turbo is the most accurate for EGTs no matter how you look at it.

 

[Wingate]

heres my 2 cents worth..
Pre-turbo has its arguements as well as post.
Pre-turbo is only as accurate as the average of the cylinders you are sampling from. With the manifold being a 4/2 split, you have no clue whats going on with the un-sampled cylinders. The true best way to monitor cylinder temps is to have a thermocouple installed directly outside the vavle port on EACH cylinder and use a thermocouople scanner to look at all temps for min/max and deviation/variation. The 5.9L engines tend to run hottest in the #1 and #6 cylinders, so simply getting an average of 3,4,5,6 isnt as accurate as you would initially think. Add in the potential for thermocouple failure grenading the turbine wheel on the spool. (although this is a very remote possibility unless something hits it)
Post turbo is more of a general average of all cylinders. While you should not see the peak temps as with a pre install, I find them to be very accurate when towing hard in the Texas heat. The key for me was to install the post turbo thermocouple at low mileage and in stock trim and run the truck for several months thru various load conditions to get a trend of whats normal. Then I added programming and could see the difference that altered fuel timing/duration made. I know whats normal and whats not.
Not sure what side thermocouple one can use in such a small runner port on the manifold , i would guess 1/8" and only probably an inch of probe inside the manifold. With the post turbo install, I was able to use the larger 1/4" probed and have 3-4" of probe sampling the exhaust stream. Mine is installed in the exhaust elbow directly behind the turbine housing.
On large displacement diesle and NG engines, we monitor individual cylinder port temps as well as turbo inlet and turbo outlet, catalyst in and catalyst out. Nothing happens without me knowing about it!

 

[RVTRKN]

Well it sounds good and all, checking each cylinder EGT, but impracticable. Kinda of like putting a fuel pressure gauge on each injection line, when just the Common rail pressure will give you same info. As long as I have been on TDR and other web sites, I've never heard of a Thermocouple probe grenading, as far as location, the best place pre turbo, is at the "Y" of the manifold.

 

[Motorhead]

I have used the SAME SPA digital gauge and EGT probe on TWO trucks, a 2001.5 that I sold with 120,000 miles and it is now on my '07, 5.6 with 70,000 miles currently. BOTH trucks have had the probe mounter Pre-Turbo. On my '07, I removed the right inner fender plastic so I could access the manifold straight on. My manifold has that thick space and that is where I drilled and tapped. I just coated a "R" letter drill with grease and drilled the manifold. I greased the pipe tap, tapped the hole and then started the engine momentarily to blow any remaining chips out. A few cast iron drill chips blown past the turbo wheel is not going to hurt anything. Done a bunch this way. With my DIGITAL gauge and having it pre-turbo, I know QUICKLY if I exceed safe temperatures. I have seen where guys get lazy and drill into the exhaust manifold at one of the connecting tubes. DON'T do that as the manifold isn't very thick there and you won't get very many threads to hold the probe. My $0.02 worth!

 

[Wingate]

Well it sounds good and all, checking each cylinder EGT, but impracticable. Kinda of like putting a fuel pressure gauge on each injection line, when just the Common rail pressure will give you same info. As long as I have been on TDR and other web sites, I've never heard of a Thermocouple probe grenading, as far as location, the best place pre turbo, is at the "Y" of the manifold.

I have, although not very common, I have seen one go thru a $50,000 turbo and effictively destroy it.
monitoring fuel pressure at the individual lines on a CR system cannot be a logical comparison to monitoring individual exhaust port temps. While you will get the same reading on the injection lines, there is potential for HUGE variation between cylinder temperatures.

 

[RVTRKN]

I realize that each exhaust port has the potential of being a different temperature, in fact that would be a great setup in helping to detect individual injector issues. I'm a little anal with knowing more than stock allows or accounts for, (see pic) like the oil pressure algorithm on the newer trucks that is nothing more than a camouflaged idiot light, and is the reason I have an oil pressure sending unit installed so I can see the real oil pressure. The task of adding individual EGT sensors at each exhaust port and the software needed to install it is a little more anal than I would be. I actual have that ability if I wanted to install the software where I could see them all at same time, but to install the sensors properly, would require a special exhaust manifold or special undersized Thermocouples. The cost of that though, would probably pay for half the cost of replacing the engine if it ever failed. Again, I'll repeat it again, it's impracticable to go through the cost, hassle and installation of that, just to see a few degrees difference, in the chance something might fail, and that would be astronomical in the odds that it would. In the picture below is what I can see at present, and I could easily change the gauges to all be EGT sensors. I'll take my chances that my Thermocouple will not fail.

 

[AH64ID]

With the manifold being a 4/2 split, you have no clue whats going on with the un-sampled cylinders.

A common, including myself for many years, misconception. The 3rd gen manifold is indeed a 3/3, thou I think a 4/2 would flow better.

OEM is on top.

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