If I want to use a non-contact infrared thermometer to read the temperature of each cylinder at the exhaust port during idle, how high of a reading should the thermometer be able to handle?

  • I'm adding this as a comment rather than an answer, because I can't seem to find a definitive source, but from what I see in different chat-like forums is that exhaust manifold temperature is typically around 1200°F - 1400°F at highway speed, probably less at an idle. From what I've seen on shows like "How It's Made," they can get red-hot.
    – BillDOe
    Sep 29, 2015 at 20:09
  • You may want to reword your question, Robert. As it stands you are asking us to figure out what the probe can handle (question in the body) without any information about the probe itself. If you are actually asking what is in the title, it would make more sense, but still very vague. It really depends on the engine, engine speed, how well the engine is running (rich or lean), etc. Very broad. Sep 29, 2015 at 21:09
  • Diesel, gasoline, LPG?
    – Nick
    Mar 20, 2017 at 13:53

3 Answers 3


According to this website from the University of Washington:

Manifolds and/or exhaust pipes on some vehicles can reach 1200 degrees F. It is rare to find temperatures this high in normal operation.

If your laser thermometer can read up to at least that high, you should not have any issues.

EDIT: As pointed out by @Zaid below:

... if a cylinder is running lean it can drive exhaust manifold temps up to 1600 F.

This would be a very lean condition, but is possible.

  • 2
    One thing to consider here is that if a cylinder is running lean it can drive exhaust manifold temps up to 1600 F.
    – Zaid
    Sep 30, 2015 at 13:33
  • @Zaid - You are exactly right. Also, you can use exhaust temperatures to improve overall performance. You can adjust your fuel trims across the board on a single cylinder by adding/subtracting for that cylinder. Add fuel to drop a temp/ reduce to raise a temp. In doing so, the entire engine will be running as evenly as possible. Checking the temp of each exhaust port will give you what to do with each cylinder (injector, really). Thanks for the edit, btw. Sep 30, 2015 at 16:03
  • @Zaid Important point which should be added into the answer. Sep 30, 2015 at 16:35
  • Would 350F at idle be normal? Nov 23, 2015 at 11:33
  • @RobertS.Barnes, I'd suggest posting that as a separate question, as it's different from what's being discussed in this one.
    – Mathieu K.
    Jul 19, 2016 at 18:33

I just IR my exhaust manifolds and temp was 290 deg after about a 30 min run..outside temp here in Phoenix today is 95 deg. Bobby O

  • Search on youtube for engine on test beds and look at some of the colours that the exhaust manifold shows...
    – Solar Mike
    Mar 20, 2017 at 12:42
  • Your exhaust manifold or the heat shields for the exhaust manifold?
    – Nick
    Mar 20, 2017 at 13:52

I just checked the exhaust manifold of my 1934 Buick with a straight 8 after about a 15 minute drive. The temperature about 4 minutes after shutting of the engine was about 450F degrees, checking with an infrared laser thermometer. It's about 75 degrees outside. The engine temperature while running was about 140 to 150 degrees, as indicated by the original, but restored, dash temperature gauge.

  • Welcome to the site. I'm not sure how this answers the question? The OP is asking how high the thermometer needs to go while the vehicle is running. I'm sure it will be far in excess of 450F. The temperature on the dash is the temperature of the coolant, not exactly what the exhaust manifold is reading. Jun 19, 2017 at 1:07
  • @Paulster2 Your 450F seems low, especially as you yourself make the case for 1600F in very lean conditions ....
    – Solar Mike
    Jun 19, 2017 at 6:59

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