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02-10-2016, 08:48
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#1
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Registered User
Join Date: Oct 2015
Posts: 152
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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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02-10-2016, 08:57
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#2
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Registered User
Join Date: Nov 2015
Posts: 7
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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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02-10-2016, 10:11
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#3
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Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
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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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02-10-2016, 10:16
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#4
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Registered User
Join Date: Mar 2014
Location: Anacortes
Boat: previous - Whitby 42 new - Goldenwave 44
Posts: 1,835
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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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02-10-2016, 11:15
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#5
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֍֎֍֎֍֎֍֎֍֎
Join Date: Apr 2006
Posts: 15,136
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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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02-10-2016, 11:50
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#6
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Moderator
Join Date: Feb 2012
Location: Carrabelle, Florida
Boat: Fiberglas shattering 44' steel trawler
Posts: 6,083
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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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02-10-2016, 18:05
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#8
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Registered User
Join Date: Jan 2008
Location: SF Bay Area (Boat Sold)
Boat: Former owner of a Valiant V40
Posts: 1,143
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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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02-10-2016, 18:08
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#9
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Senior Cruiser
Join Date: Nov 2013
Location: Port Moresby,Papua New Guinea
Boat: FP Belize Maestro 43 and OPBs
Posts: 12,888
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Re: Measuring eng temp with IR guage
Quote:
Originally Posted by jamhass
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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Patches of black tape stuck on appropriate target points?
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02-10-2016, 18:22
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#10
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Registered User
Join Date: Jan 2008
Location: SF Bay Area (Boat Sold)
Boat: Former owner of a Valiant V40
Posts: 1,143
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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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03-10-2016, 03:48
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#11
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,126
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Re: Measuring eng temp with IR guage
Greetings and welcome aboard the CF, dlparch.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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04-10-2016, 11:55
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#12
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Registered User
Join Date: Mar 2014
Location: Anacortes
Boat: previous - Whitby 42 new - Goldenwave 44
Posts: 1,835
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Re: Measuring eng temp with IR guage
Quote:
Originally Posted by jamhass
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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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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04-10-2016, 12:09
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#13
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Measuring eng temp with IR guage
Quote:
Originally Posted by StuM
Patches of black tape stuck on appropriate target points?
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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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04-10-2016, 13:25
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#14
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Registered User
Join Date: Nov 2015
Location: Zimbabwe
Boat: Calypso Cat 21'
Posts: 49
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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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04-10-2016, 13:28
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#15
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Moderator Emeritus
Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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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.
Sent from my iPad Pro using Cruisers Sailing Forum
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