182L 470 eng, JPI monitor, high CHT #4

I am flying a 182 L with the 470. No turbo etc. I have the JPI engine monitor, and upgraded from 700 to 730. Uses the bayonet probes on all cylinders except for a gasket sensor on #4. I know it is supposed to read higher as it is on/mounted with the spark plug. Mike Busch recommends temps below 380 for the continental engines. In climb, all CHTs are about 370, but #4 is over 400. In cruise, 8000-9000 msl, CHTs in 330-340 except #4. I have been leaving a bit of cowl flap open to keep lower. About 50% cowl flaps gives #4 just about 380. So the question: If all bayonet sensing cylinders are good and the gasket sensor cylinder is 50-75 higher, is it OK to disregard and close the cowl flaps? spoke to JPI, they just say expect 50-100 degrees higher on the gasket probe cylinder. they don't (won't) say that is acceptable.

Comments

  • Scott ShererScott Sherer COO Forum Moderator

    Stand by while I send this to our association A&P, Erich Rempert.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Scott ShererScott Sherer COO Forum Moderator

    From our A&P Erich Rempert:

    Absolutely, close the cowl flaps.

    If you look at the TCDS for the engine (I have a Navion with an IO-470) it lists the max CHT with various probes, the 460 number we're all familiar with is using a bayonet probe, with a spark plug gasket probe it's 525, and with a barrel type (never seen one) is only 290! (Limits here are for IO-470-C, refer to the TCDS for your specific engine limits, see attachment)

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Not familiar with TCDS abbreviation. It looks like your source is allowing a 65 degree increase for gasket fitting readings compared to bayonet style. (Even if above the red line on the JPI monitor) So I can likely go with that. Will review the TCDS document as soon as you are kind enough to advise what it is. I have the operator manual, as well as the maintanence manual for the engine.

    Your comment also noted "see attachment" which I do not see. This may contain the needed info.

    V/R
    pb

  • Scott ShererScott Sherer COO Forum Moderator

    Hello PB,
    My apology. Here's the attachment that Erich is referring to. My error.

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Very helpful, thank you. Can you advise the source document? I will try to find on line for reference. Just did a 50 hour oil change, cut filter for inspection (no issues) and compression test. Two cylinders just below 60, but runs smooth and uses a quart of oil every 16-20 hours. I suspect the issue is due to prior to my ownership, it flew 400 hours from 1999 thru 2019. I purchased in December and have more than 100 so far.

  • Scott ShererScott Sherer COO Forum Moderator

    These came from the TCDS, or FAA Type Certificate Data Sheets. Here's a link: https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/Frameset?OpenPage

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

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