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High EGT

in 912 / 914 Technical Questions 8 years ago

  • Re: High EGT

    by » 8 years ago

    Gents,

    I no response, so what the heck. Pulled the carbs apart, and moved the clip down one position, to #3. I will give it a run and see how that affects the egt. Like I said, probes are about 3 inches from cylinder, and ran 1600 degrees. didn't exceed the max, and runs much cooler when I run it hard... but I like pulling the power back to 5200 and thats when the temps go up.
    best

    sd
      
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  • Re: High EGT

    by » 8 years ago

    I think you nailed it when you said, "...all that is happening here is I can see what's going on...".
    Nothing has changed. Ignorance WAS Bliss!

    The manual says 880°C. That means the number between 870 and 890.
    Do not add more significant digits (resolution) than is really there.
    Converting to Farenheight and declaring that 1616°F is the spec is a conversion error. ***
    It is not going to melt down at 1617°F.
    It is not even going to melt down at 1700°F
    ~880°C (more or less) is just the place that the engine has historically been shown to peak on the leaning curve.
    If you are below ~880°C, you are still on the rich side of peak.
    Don't worry, Be happy!

    The 912iS engine is identical to the 912ULS except that it is fuel injected and is intentionally run on the lean side of peak all day long.
    It is spec'd at 950°C (1740°F). And even it is not going to self-destruct at 1750°F.

    As long as your temp does not go over 885° (1630°F) you are still technically within the 880°C limit. ***
    And never forget that this is the way it has been happily running for the last 250 hours when didn't know what the temperatures were.

    ***
    880 = 2 significalt digits.
    880°C = 1616°F (4 significant digits) is an improper conversion.
    880°c = 1600°F (2 significant digits each) is the proper conversion.
    If you insist on using Farenheight as temperature, remember that 1600 is the number between 1500 and 1700.

    The original number was 880° which implies a 5° error band.
    885°C = 1625°F. Or more properly 885°C = 1630°F (3 significant figures each.)

    Bill Hertzel
    Rotax 912is
    North Ridgeville, OH, USA
    Clicking the "Thank You" is Always Appreciated by Everyone.

      
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  • Re: High EGT

    by » 8 years ago

    Sheldon
    I went through the same thoughts when I first installed a digital engine monitor.(912UL) Here's what I know. When I installed my engine there was no requirement to monitor EGTs. Typical on 912s to only monitor EGT on cylinders 3 and 4. Probes, I assume you are using ones supplied from GRT. This is a must there is no selection for probe type in the GRT. Typical for EGTs to be cooler when the engine loaded down (climb etc), then increase some as you throttle back to cruise. Mine have run with a similar differential, typically up to 1550 on the hot side. Check your spark plugs, what are they telling you? I'm using the #3 setting on the needle valve (field elevation 1000ft). Other things you can check: carb. piston moves freely and easily, the carb. bowl vent tube is not being influenced by air flow under the cowl. Possibility of debris restricting fuel flow through valve.
      
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  • Re: High EGT

    by » 8 years ago

    Gentleman

    Thank you... All of you. I love this engine, and this forum. I bought this plane and engine, skeptical. I am in awe of it now.
    Today I flew the heck out of it, with the clip in the number 3 position, and its a better plane. I am running about 1550 when I throttle back to about 5200. I do get a egt split in this range, which I just adjusted the setting to 275 ( max diff was about 220) . The egt is very even at 5400 and up, and 4300 and down. I do like pulling the power back to 5000, to 5100 for cruise, and that seems to be the range that the split is. It is running so smooth, I have no complaints.
    I bought a hackman leaner which is not installed as yet, any opinions? Clearly it isn't needed up here, but any one have opinions on this system?

    best

    Sheldon
      
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  • Re: High EGT

    by » 8 years ago

    Hi Sheldon,

    The sweet spot for your ground adjustable prop would be a WOT setting of 5600-5650 rpm in level flight. Then throttle back to your cruise rpm. If all you get is 5200 rpm WOT you are way over pitched. and you're stressing the engine. I would also set the idle rpm for 1650-1800, but never just sit and idle at low rpms. The 1650 will be good for shut down and you should sit and warm up at 2000-2400 rpm so you don't bang on the gearbox. An EGT split in the 200F's is way too much and something is out of whack. Normal may be anywhere from 0 - 80F and possibly for some on occasions 100F.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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