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  1. #1
    bob27s's Avatar
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    TT40 - winter season roundup

    Worthwhile doing this every so often - and since it is cold outside (at least here in Cleveland) seems like a good time.

    Many of us fly Club 40 and 424 with the TT40pro engine. Perhaps a little data exchange. No speculation, no theories, no guesses, no BS just some real time data you have personally collected, recorded or observed over the past flying season.

    I have been pleased to see the enthusiasm and growth of the Club 40 group we have put together here in northern Ohio, and I have been pleased to help folks out as they learn and develop into the sport.

    I have broken-in and setup at least 15 of these the past couple of years. Some for myself, most for other people. I know what the stock engine is capable of on the bench, and although 15 engines is not a statistically significant sample, I am going to claim it as such There was some variation, but in general fairly consistant results.

    Consider these all NEPRO configuration. Stock. Stock head gasket, stock muffler, baffle, not-messed-with fully functioning carb. Most newer models with stock rear bearing. Same 9x6 prop. Sometimes varied conditions (but real world averages out). Fuel 15% omega.

    Two significant measurments were observed to be consistant: None of them peaked over 17,000 rpm with APC 9x6. All of them would peak over 16,000 rpm.

    So allow me to open this up...

    Provide your results. Prop, fuel, usage (424 or club 40), your geographical location, and typical observed rpm on the test bench, and rpm installed in the aircrft (sometimes different). If possible, the number of engines you race, and any noteworthy variation between them.

    Let this start, and I will add some of my data into the mix.

    Bob

    Bob Brassell
    Jett Engineering - Engine Mfg Support Forum Host
    rjbrassell@gmail.com or bob27s@hotmail.com
    RB-78

  2. #2

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    RE: TT40 - winter season roundup

    Bob, as you know there are two different baffles that come in the muffler.  One is the disk/cyclone Baffle and the other is the cone baffle.  I think the newer ones all use the cone baffle.  I sent a cone baffle last year (2010) to Jim Duda in Texas ans he ran some tests.  All the same afternoon with pretty constant parameters of temps and humidity, same engine. just the mufflers were different.

    The results basically came out the same.  Maybe the disc baffle was 50 rpm faster but using the tachs margin of error as a fudge factor they were identical being within the margine of error.  That could be a honest question in the future from someone.
    Barry...
    http://www.RCPRO.org

  3. #3
    vicman's Avatar
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    RE: TT40 - winter season roundup

    Gosh Bob, The first thing I do is pull the bearing and lock down the muffler before I ever fire it up. All my data would be skewed.
    A guy who used to live on this site and now is rarely here due to the "upgrade".
    Most likely fading away till the My Forums is fixed. Too bad.

  4. #4
    bob27s's Avatar
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    RE: TT40 - winter season roundup


    ORIGINAL: vicman

    Gosh Bob, The first thing I do is pull the bearing and lock down the muffler before I ever fire it up. All my data would be skewed.
    well data like that is ok, as long as it is qualified like that
    Bob Brassell
    Jett Engineering - Engine Mfg Support Forum Host
    rjbrassell@gmail.com or bob27s@hotmail.com
    RB-78

  5. #5
    vicman's Avatar
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    RE: TT40 - winter season roundup

    Ok,
    After I change the bearing, lock the muffler down and check head clearance to .007 I usually see 16,700 with a relative rich setting using a 9x6 apc. I can easily lean out to 17 but don't relish burning up engines. I've done it before but they don't last long enough to make it worthwhile.
    I break in with a 8x5 prop using Byron 18/15 fuel for break in and most of my practice flying. I haven't hurt any engines for the last two years using this formula.

    17k on the engine has not helped me on race day yet so working on thumb failure has been my main area of attention.
    A guy who used to live on this site and now is rarely here due to the "upgrade".
    Most likely fading away till the My Forums is fixed. Too bad.

  6. #6

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    RE: TT40 - winter season roundup

    Hi Bob,
    OK as you know we run box stock here in Nepro and other than the muffler bolt fix most of us run stock bearing as well. The engines run best when they are propped down to about 16,400-the props make a huge difference. Look for ones that pitch heavy. Best times I turned on the short course were in the high 1:14 range when I raced full time. I think Ralph, Ray and Lloyd maybe have gotten down to the 1:13's now, and 1:14's on a regular basis. Plugs, K&B 1L or Mc -59. Tried the Merlin's no real benefit was found.


    Lewis
    WWW.LCSPERFORMANCE.COM


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