Supermutt Posted July 24, 2023 Share Posted July 24, 2023 I thought I would share what I recently read and possibly most of you already know. I just installed a new pyrometer in my 96 DM. I got it from PAI. After thinking I would have to weld a nut on the exhaust I found that it was tapped with a 1/4” plug about 3” downstream from the turbo. It was on the back side so I didn’t see it at first. So as usual I installed everything without reading the instructions. After I was done I browsed through them. I found a warning/notice stating that if the probe was installed post turbo the gauge would be reading 150-200 degrees cooler than the actual exhaust temp ! It stated that if possible to locate the probe pre turbo in the exhaust manifold. Welp there is no way that’s going to happen on my e7 350. I personally have never seen one on a Mack installed in the manifold. Or for that matter on a cat or Cummins. Always just after the turbo. So for the last 40 years when I was looking at the exhaust temp and thought it was 850 it was really 1050 degrees ? How many of you are aware of this. Am I the only one that never gave this any thought ? Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/73086-pyrometer-location/ Share on other sites More sharing options...
D-Day Posted July 24, 2023 Share Posted July 24, 2023 that is very unusual definitely never seen any pyro in any other place than about 2 or 3 inches after the turbo on any cummins or mack and detroit with the exception for the 864 v8 no turbo 2 pyros at the exhaust manifolds 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73086-pyrometer-location/#findComment-535532 Share on other sites More sharing options...
Supermutt Posted July 24, 2023 Author Share Posted July 24, 2023 For what it’s worth here is a pic of the instructions that refer to location & temp delta. Quote Link to comment https://www.bigmacktrucks.com/topic/73086-pyrometer-location/#findComment-535534 Share on other sites More sharing options...
Solution Popular Post Geoff Weeks Posted July 24, 2023 Solution Popular Post Share Posted July 24, 2023 Pyro's thrermocouple are placed down stream of the turbo so if the tip fails (burns off or breaks) it doesn't take out the turbine wheel. 1300deg F is considered the max temp, ahead of the turbo, with 1100-1200 post turbo. Some manifolds have plugs pre turbo for diagnoistic purposes but for running full time, I have only seen them after the turbo. 2 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73086-pyrometer-location/#findComment-535539 Share on other sites More sharing options...
Supermutt Posted July 24, 2023 Author Share Posted July 24, 2023 Geoff thank you for clearing up the confusion. Makes perfect sense on why not to place the probe upstream. Quote Link to comment https://www.bigmacktrucks.com/topic/73086-pyrometer-location/#findComment-535543 Share on other sites More sharing options...
Geoff Weeks Posted July 24, 2023 Share Posted July 24, 2023 I've never seen one come apart, but I don't think it is worth the risk. I noticed they said the guarantee the thermocouple, yeah great you'll replace the $50 part but I'm on the hook for the replacement turbo, no thanks. I routinely saw north of 1000 deg pulling hard with no problems. oil cooled pistons keep the aluminum ones from cracking, newer stuff uses steel composite pistons, steel crown with aluminum body. Even the older ones used a steel 1st groove. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73086-pyrometer-location/#findComment-535545 Share on other sites More sharing options...
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