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Cold Cylinder

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  • Cold Cylinder

    My new 260SE has an issue im not sure on. The #3 cylinder shows about 100 degrees colder than the others on the CHT. The engine runs incredibly smooth and starts up in about 1/2 a turn. Im getting about 150-175 RPM drop on the mag check but its the same on both.

    One thing I am wondering is if I should be leaning on takeoff at 5500 feet field elevation? My CHTs on the other cylinders are barely 300 but the #3 is under 200??? Climb performance seems a little low to me so I am thinking maybe I have a cylinder problem?

    I went out this morning and had these problems but after landing I came in and then did another run up but leaned quite a bit and the #3 cylinder was much closer in temp to the others. I didn't have time to take it back up but before i called the mechanic over i thought i would ask if perhaps i am just running too rich or something else wrong? I don't think its a bad probe but it could be.

    the only other thing i have noticed is at certain prop and throttle settings i was getting a little surging on the prop and the rpms were bouncing around?

    Any help is appreciated

  • #2
    It's likely you don't have a problem with number 3 cylinder. Most approved EDM700 installations HAVE to retain the old Cylinder Head temperature instrument probe. On my engine this is on cylinder 3 and the EDM cylinder head temperature probe is fitted in addition to the standard probe on this cylinder.
    This can affect the EDM700 temperature readout on that cylinder by in my case 60c. In other words all the other CHTs can be around 360 but cylinder 3 shows 300.
    I can send you some pictures if you provide an e mail address.
    Talk to your IA. I'm not sure you can simply remove the old factory probe legally but it seems to be a grey area.
    A slightly different point, your CHTs seem a bit low around 300. There is a school of thought that says you can run Big Continentals too cold and run into compression issues. I had my CHTs around 300 in winter and sometimes less if LOP. Oil temperatures were also too cold around 130. I have tightened up the cowl flaps and now the temperatures are much better. However, in the winter cold I still need to blank off about a third of the oil cooler to keep the oil temperature around 170-180 where it should be.