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Exhaust Manifold Configuration

in 912 / 914 Technical Questions 12 years ago
My 912ULS is installed on a Zenith CH750. The exit angle of the exhaust manifold from #1 and #2 cylinders appears more abrupt than it needs to be and #1 EGT runs above 1500 degrees F at full throttle. Would modifying the manifold for a smoother transition relieve backpressure and reduce EGT? Photos attached.
Manifold1.JPG (You do not have access to download this file.)

  • Re: Exhaust Manifold Configuration

    by » 12 years ago

    Hi Ken,

    I don't believe changing the angle on the exhaust pipe in the pic would help. Maybe someone else may know something else.

    I can't tell by looking at the picture alone, but it doesn't quite look (I maybe wrong) like the EGT is 100mm (3.93 (4) inches) away from the exhaust flange as described in the installation manual? Being too close will make the temps higher.

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

      
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  • Re: Exhaust Manifold Configuration

    by » 12 years ago

    Good eye, Roger. I got my EGT probe distance from Rotax Installation Manual, dated 9/1/1998, page 10-1, which indicated 850 C (1562 F) max, and 880 C (1616 F) at take-off, taken 70mm (2.76 inches) downstream of exhaust flange. That’s where I put my probes. Do those temps look appropriate compared to what the 100mm distance would give?

    Thanks for giving me some comfort in the design of the manifold.
      
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  • Re: Exhaust Manifold Configuration

    by » 12 years ago

    The temps look about right for being closer than 100mm. The4 closer the probes the higher the temps and the further away the cooler.

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

      
    Report
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