1HD-T Pre vs Post Turbo EGT Readings (1 Viewer)

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I have both pre and post turbo gauges rigged up on my truck right now, so I thought I'd do a couple hill runs for my own comparison and I set up the GoPro so I could show others as well :)

It's noted in the video as well, but the analog gauge is pre-turbo in Celsius and the digital reading on the 3in1 is post-turbo and Fahrenheit, so it's not a straight comparison, but it's what I had to work with. Just a little math required.



Note, not only the temperature difference pre to post turbo, but also the reaction time difference between the two. Post turbo probe is located 3" from the joint off the factory elbow.

Bit of a summary of my truck:

1994 HDJ81
Intercooled
MMP turbo presently fitted
Tuned
285/75/16 Duratrac tires at the time of the video.
 
I am on my phone at the moment so the video is a bit small. What is the average difference between pre and post? I have my gauge post and always wondered what the difference is. I always assume I am 200-250 lower than pre.
 
I always assume I am 200-250 lower than pre.

the difference is not linear. under different conditions, the temperature difference pre and post can vary.

in the clip above, at 0:44 Pre turbo EGT had peaked at ~650c, the digital reading post turbo was ~585 f or ~300c. thats a huge difference a that point in time. 350C discrepancy!


Post turbo temp peaked at 1:15 at the end of the run, and temp was ~720f or 380c
the pre turbo gauge was steady at ~680c for quite a while before the post turbo EGT peaked.
thats a 300c discrepancy again
 
the difference is not linear. under different conditions, the temperature difference pre and post can vary.

This for sure. I ran the post turbo EGT gauge only for about 4 years and I guessed (also from reading on the mud forum :) ) that the difference between pre and post turbo EGT's would be about 400 degrees F when looking to run at the high end of max 1200 F pre-turbo. It still looks like this is about right for when the temperatures plateau, but I didn't expect the post turbo temps to be that delayed. Some delay, yes, but not that much. I suspect I ran hotter for longer than I thought when I had only the post turbo EGT readings to go by.
 
This is great! Thank you @MonsterCruiser!!

One day I will get a pre-turbo EGT probe installed :) How easy (or hard) was the pre-turbo probe install? Did you do it yourself? Did you take off the exhaust manifold to drill it, or did you drill into it with the manifold on the engine?
 

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