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Thread: CHT, thoughts, tips, HELP....

  1. #1

    Default CHT, thoughts, tips, HELP....

    We have just installed 4 new ECI Titan cylinders on our 160 Tri Pacer....ohhhhh they look nice...and we installed a JPI EDM 700 to monitor their temps/health...

    We are at about 35 hours since NEW on the cylinders, they broke in almost immediately, and they are working very well. The problem is the CHT's are still a bit higher than we would like to see....430 on climb on #3, and about 400 in cruise....

    We discovered that we were missing the "air scoop assembly" that attaches to the brackett air filter and covers up alot of the irregular shaped hole that the nose wheel tubes exit through. We will attach the "scoop assy." and try to seal up any additional holes in the lower part of the cowl....to attempt to keep as much negative pressure in the lower cowl so we can more effectively draw air from the upper high pressure cowl area, through the cylinders, and out the exit near the firewall....and hopefully do a better job of cooling all 4 cylinders...

    We have rebuilt all our baffles, used McFarlane Cowl Saver materials, which is very nice baffle seal material, and have caulked all we can find to minimize/eliminate any air leaks, other than the two mag blast tubes, and the two scat tube connections right above #3 cylinder for forward cabin heat, and carb heat.

    Our oil temps are running very cool, and we may need to adjust to a higher limit....only about 170 degrees in cruise....

    We are interested in any hints, tips, modifications etc that have yielded cooler CHT's in PA22's....Thanks

  2. #2
    Pacerfgoe's Avatar
    Join Date
    Nov 2009
    Close to Edmonton, Alberta

    Default Re: CHT, thoughts, tips, HELP....

    When I installed a cylinder head temp gauge I was shocked to find out how hot it was running (O-290D). All the baffling was new and I thought in good shape. My focus then moved to the lower cowl, and the air that was getting in around the air filter, oil cooler,and the little cutout for the starter. There is supposed to be a leather seal around the airfilter to seal against the cowl, and my opening at the oil cooler is a touch too big ,so I'm going to work on that also. the starter hole i'll just get one of the newer smaller starters and just patch up the hole.
    Now while pondering all this I went ahead and "repaired" my carb as it was leaking gas,and needed the throttle shaft replaced. While looking the carb over I discovered that the wrong nozzle had been installed somewhere along along the way, and it was considerably smaller than what was supposed to be in there (.081" compared to .107") I think this is really what was making my engine run hot.....it was lean all the time, and I didn't know enough to figure it out. I've fixed it now so we will see if it runs cooler when I get it airborne again this summer.
    So what I'm saying is have a quick look at your carb to ensure things are OK there as well.

    P.S. I see its your first post.....Welcome
    Last edited by Pacerfgoe; 02-17-2012 at 01:27 PM.

  3. #3

    Default Re: CHT, thoughts, tips, HELP....

    good things to consider by Pacerfgoe above. Might check for an induction leak that would make it run hotter.
    Run you mixture thru entire range of rich to peak egt to see if you have at least 150-200 range of egt between rich and pieak,( I think i get at least a 270-290 degree spread ) if less than that could be carb to lean for some reason. also what type cht probe are you using. The spark plug washer style plug will indicate anywhere from 50-75 degrees hotter than the cylinder head probe. I had one that was almost 75 degree difference between the two style probes on the #3 cylinder
    "Progress is our most important problem"

  4. #4

    Default Re: CHT, thoughts, tips, HELP....

    Hi Mark;
    Your post said this:
    We discovered that we were missing the "air scoop assembly" that attaches to the brackett air filter and covers up alot of the irregular shaped hole that the nose wheel tubes exit through.
    Can you please describe this, or maybe post a picture of it ? I have never seen this or a reference to it and if I am supposed to have it I don't or if I do,I don't know it. Thanks.

  5. #5
    rocket's Avatar
    Join Date
    Dec 2010
    5NK in the Bristol Bay, AK

    Default Re: CHT, thoughts, tips, HELP....

    this thing around the filter housing. It has leather around the cutout for the olio strut and thick felt where it lays against the bottom of the cawling.

    Do not forget that horizontal strip that attaches to the lower nose gear tubes with adel clamps and lays laterally across the bottom of the carb heat box. My nose gear is not attached so it is not shown in this foto. A bad drawing can be found in the parts book.


    filter fairing.jpg
    Last edited by rocket; 02-20-2012 at 09:42 PM. Reason: add other fairing info...and spelling

  6. #6

    Default Re: CHT, thoughts, tips, HELP....

    Thanks for that Rocket. I appreciate it. I definitely do not have that piece, however in looking at my cowling etc. I can't figure out how it would fit. I will have to get inside there and noodle it a bit. For Steve, did you find one of these or buy one ? Thanks to all for the information.

  7. #7

    Default Re: CHT, thoughts, tips, HELP....

    Univair sells the piper air scoop assembly, 150.00! We bought one for our tri pacer, will see what difference it makes soon, I hope. Only applies to PA22, not PA 20 Pacers, they use a large flat leather seal tha mounts to the air filter bracket to seal off any air fro going around the space between the filter and the cowl.

    All of these pieces, along with the air dam at the back of the lower cowl scoop ( pa22) appear to keep high pressure air from the lower side of the cowl so as much air from the upper high pressure side of the baffling is pulled down around the cylinders to cool them.

  8. #8
    Steve Pierce's Avatar
    Join Date
    Nov 2007
    Graham, Texas, United States
    Blog Entries

    Default Re: CHT, thoughts, tips, HELP....

    I have never seen the part Rocket posted a picture of. There is a fairing/scoop with baffle material that Adel clamps to nose nose gear mount tubes that I believe is there to control air flow.

  9. #9

    Default Re: CHT, thoughts, tips, HELP....

    I too was shocked when I saw my CHTs after installing an EI system. I have the bayonet probes and I was going up to 425 - 430 climb out. I am still working on it and have the plane taken apart for it's condition inspection right now. I have changed the air intake to smooth things out and will be working on sealing around the Bracket air filter. My Pacer is technically an experimental so I have a little more latitude in what I try.

  10. #10

    Default Re: CHT, thoughts, tips, HELP....

    Let us all know what you find out. Certainly good to keep things like CHT as cool as we can for longevity....

    Mark S.

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