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Manifold Pressure Sensor Recommendation

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  • Manifold Pressure Sensor Recommendation

    Apparently I installed the wrong MP sensor/transducer. The sensor I installed is the Kavlico P4055 as shown below (and used by Garmin). I mounted it on the engine side of the firewall. I was getting a wacko reading and confirmed on the Dynon forum I installed the wrong sensor. (I'm using the Dynon Skyview HDX for my EFIS). I already have a Dynon pressure probe (also shown below), but it needs to be mounted on the cold side of the firewall. I would like to avoid that as I have already buttoned up my boot cowl and instrument panel and to install one of these will be a huge setback with considerable dismantling.

    Anyone have a suggestion for a MP sensor/transducer that can handle engine compartment mounting?

    This is the pressure sensor I currently have installed. It is NOT giving me an accurate reading. (See the pic of my Skyview below with the erroneous reading.)

    Screen Shot 2020-08-01 at 11.51.59 AM.png

    This is the pressure sensor from Dynon to be mounted cabin side of the firewall. Trying to avoid mounting this and looking for an alternative to the P4055 shown above that I can mount on the engine side of the FW.

    Screen Shot 2020-08-01 at 11.55.27 AM.png

    Not Indicating ambient pressure when engine is not running and showing 8 inches.

    Screen Shot 2020-08-01 at 12.03.33 PM.png
    Last edited by robcaldwell; 08-02-2020, 07:39 AM.
    Rob Caldwell
    Lake Norman Airpark (14A), North Carolina
    EAA Chapter 309
    Model B Quick Build Kit Serial # 11B-24B / 25B
    YouTube Channel:
    1st Flight May 18, 2021

  • #2
    Those sensors used by Garmin come in different pressure ranges, are you using the correct range for the Dynon? Just went through this on a Bonanza and had the wrong range sensor in there at first. They should be able to play together.


    • robcaldwell
      robcaldwell commented
      Editing a comment
      This is the one I am using. You can see in the picture that it does not indicate correctly. Trying to find the correct Klavico for my Dynon. Will post on their forum as well.

    • N942VT
      N942VT commented
      Editing a comment
      I can't remember off the top of my head the other ones, let me take a look when I get back to the shop. The shop is a top Garmin dealer and has access to unique Garmin documents. Peter, if you're on - do you remember?
      Just a thought but does the Dynon unit have the ability to adjust the parameters in the calibration process? Garmin does. Might help.

  • #3
    Most MAP sensors on cars are mounted on the engine. I know the avionics companies always want everything perfect, but at some point the lawyers write it and it is just a legal disclaimer.

    You already own it, and want to replace it. It is only for EFIS display and calculations. Not safety of flight. I might just mount it in the engine compartment and replace it somewhere down the road.

    Only the bottom 3 of the pictures show up, at least on my Mac.


    • Rollie
      Rollie commented
      Editing a comment
      I second that, an engine sensor should be able to be mounted in the engine compartment. Mine is Kavlico, which they want remote mounted for less vibration, I have a tube running from the tap on the cylinder (with a flow restrictor to stop the crazy fluctuations you get without it) and the sensor is attached to the engine mount with adele clamps. Same kind of deal, you could mount it to the firewall on the engine side. I don't think it would be warm enough there to interfere with the sensor's operation. Maybe it will fail sooner than it would if it was aft of the firewall but maybe not.

      The kavlico sensors are supposed to be remote mounted to get them away from the engine vibration but my oil pressure sensor is threaded directly into the accessory case cover. there is only so much room behind the engine in a Patrol, and, as my mechanic used to love to say, it's your experiment.

    • robcaldwell
      robcaldwell commented
      Editing a comment
      Pictures fixed.
      Last edited by robcaldwell; 08-02-2020, 07:36 AM.

  • #4
    My EFI MAP's look identical to the Dynon, I thought mine had Bosch on them but I will have to check. One gotcha with MAP's that I learned from the EFI instructions was the pressure port should be facing down. It helps to drain water and condensation which can kill the sensor.

    I have seen the Dynon style mounted on the engine side of the firewall. I mounted both of mine on the cold side.

    The P4055 is a range of pressure transducers, used for both fluids and gases. Obvously engine mounted. MAPS of the same style come in different pressure ranges, a lot of times 1-3 BAR, to cover the range of turbo-ed engines. I would bet the EFIS companies have this in their configuration settings, but I haven't looked.


    • #5
      Dave, Rob,
      It depends on Dynons ability to set the factor for an accurate read. I would find it odd but not totally surprised if Dynon didn’t play with the same standard.


      • #6
        Donna and I have the Dynon MP sensor on the engine side of the firewall and after over 500 hrs on our Patrols we have had no issues.


        • #7
          Most automotive sensors like these operate 0-5V. They are so standardized the wiring is labeled in a standardized format, similar to the terminals on relays. The scale you are measuring needs to be compatible, or software configurable. Since Dynon and Garmin are both used on turbocharged aircraft as well, I am assuming the scale of the MAP sensor is software configurable somewhere in the configuration menu's on the EFIS.

          I see Dynon charges 65 dollars. I think they are 1/2 of that though automotive parts sources.

          They are very reliable.