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Old 02-10-2016, 08:48   #1
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Measuring eng temp with IR guage

where is an appropriate area of the engine to measure temperature with an IR gun....head? mixing manifold? exhaust manifold??
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Old 02-10-2016, 08:57   #2
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Re: Measuring eng temp with IR guage

I would read it were the temp bulb is that is wear the engine manufacturer is reading from
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Old 02-10-2016, 10:11   #3
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Re: Measuring eng temp with IR guage

Ensure that you measure it in exactly the same manner each time, with the sensor braced against the same piece of structure, & aimed at the same angle, from the same distance. Otherwise your results will be skewed, knowingly or not, & thus not be helpful.
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Old 02-10-2016, 10:16   #4
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Re: Measuring eng temp with IR guage

Uncivilized nailed it. My only suggestion would be to measure from a few spots, like the block where the temp sensor is, the exhaust manifold, and the exhaust pipe after the water injection point. If you make a note of each every time you will be able to spot problems. You might check the transmission as well while underway under power. I do.
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Old 02-10-2016, 11:15   #5
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Re: Measuring eng temp with IR guage

Some engines have been known to have hot spots and not-so-great engineered cool systems. Ford's classic 289 V8 automotive engine was famous for burning one particular valve, because the engine overheated in that area, while water tapped for the heater in the cabin never was hot enough to really make heat in cold winters.


So, you might want to pick a couple of spots. Use a dab of paint or a marker circle to mark them on the engine. Wherever the hot water exits the block (to a water pump and intercooler or to the exhaust) would be one spot, that should never exceed the expected temperature. Where the original sender was, for sure. Maybe a couple of spots "midengine" near the cylinder heads as well. Odds are there will be some variation, especially if there is a blower bringing in cool air, or a hot alternator blowing out hot air, etc.
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Old 02-10-2016, 11:50   #6
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Re: Measuring eng temp with IR guage

Uncivilized and Hellosailor have got it nailed for you. I'd only add - this is not a good situation for a Harbor Freight level IF gauge. Invest in a good one.
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Old 02-10-2016, 12:00   #7
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Re: Measuring eng temp with IR guage

There's someone on another website who posted a pretty good "how to" explanation for monitoring your engine temp w/handheld IR scanner. He marks the engine w/sharpie and #'s for reference.

Engine Temp Monitoring & Over Heating Baseline Assessment Photo Gallery by Compass Marine How To at pbase.com
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Old 02-10-2016, 18:05   #8
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Re: Measuring eng temp with IR guage

Another little physical nit is that the "emissivity" of the surface being measured makes a difference, sometimes a significant one. Thus, say a true reading of 180 from a black rubber hose can be quite different than one from a shiny piece of stainless or a nice brightly red painted engine part.

Best practice, as previously noted, is to take a set of "base" measurements at several locations when the engine is running well and fully warmed up. That way you have a consistent reference to work with. With some luck, the measurements might even agree, but don't hold your breath.

Also note that if the surface changes significantly -- for example a "good??" salt water dousing rusts your favorite "sweet spot" -- the reading may be considerably different even if the temp is actually the same.
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Old 02-10-2016, 18:08   #9
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Re: Measuring eng temp with IR guage

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Originally Posted by jamhass View Post
Another little physical nit is that the "emissivity" of the surface being measured makes a difference, sometimes a significant one. Thus, say a true reading of 180 from a black rubber hose can be quite different than one from a shiny piece of stainless or a nice brightly red painted engine part.

Best practice, as previously noted, is to take a set of "base" measurements at several locations when the engine is running well and fully warmed up. That way you have a consistent reference to work with. With some luck, the measurements might even agree, but don't hold your breath.

Also note that if the surface changes significantly -- for example a "good??" salt water dousing rusts your favorite "sweet spot" -- the reading may be considerably different even if the temp is actually the same.
Patches of black tape stuck on appropriate target points?
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Old 02-10-2016, 18:22   #10
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Re: Measuring eng temp with IR guage

The tape would act as an insulator in addition to providing a more constant emissivity so hard to tell which wins (but try the experiment!). Perhaps starting with a nice clean surface (painted OK) and painting a nice flat black or sharpie. The "perfect" emissivity is a matte black that does not reflect. Worst is a nice shiny mirror surface. Should have noted that earlier. Thanks for the prompt.

PS: I apologize, I "R" an engineer ....
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Old 03-10-2016, 03:48   #11
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Re: Measuring eng temp with IR guage

Greetings and welcome aboard the CF, dlparch.
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Old 04-10-2016, 11:55   #12
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Re: Measuring eng temp with IR guage

Quote:
Originally Posted by jamhass View Post
The tape would act as an insulator in addition to providing a more constant emissivity so hard to tell which wins (but try the experiment!). Perhaps starting with a nice clean surface (painted OK) and painting a nice flat black or sharpie. The "perfect" emissivity is a matte black that does not reflect. Worst is a nice shiny mirror surface. Should have noted that earlier. Thanks for the prompt.

PS: I apologize, I "R" an engineer ....
I would think a matte black surface would be best as well. Glossy black tape would not be a good choice. I would go with a painted black spot as jamhass suggests myself. Try taking a battery temp reading off of a stainless steel terminal post screw and you will see the problem.
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Old 04-10-2016, 12:09   #13
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Re: Measuring eng temp with IR guage

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Originally Posted by StuM View Post
Patches of black tape stuck on appropriate target points?
Mask off and paint a 1" square of flat black if you really want to do it right. It really does matter.
I haven't heard emissivity used since flight school where we were being taught to fly with Night Vision System or FLIR
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Old 04-10-2016, 13:25   #14
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Re: Measuring eng temp with IR guage

Sorry.....
Could I ask why everyone so keen on IR temp monitoring with hand helds instead of installing a good quality temperature gauge wherever the manufacturer indicates? Surely it's a pain in the butt to keep grabbing the hand held IR instead of just looking at a gauge? Or is this purely for diagnostics? But from some of the posts seems people do it all the time....why?
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Old 04-10-2016, 13:28   #15
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Re: Measuring eng temp with IR guage

Diagnostics is my answer, but you can spot impending problems and if I'm checking, I'm checking oil temp, alternator temp, heat ex temp, transmission. More gauges than I want to install.
One day I'll get around to installing a camera in there too as my plotter will show two camera inputs.


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