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Thread: Lean of Peak

  1. #1

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    Lean of Peak

    Is it possible to run a Lycoming 0320 H2AD - carbureted - lean of peak? If yes how?

  2. #2

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    Interesting question. The easy answer is that there is a lot more to running lean of peak than just running lean of peak. I don't know about the O-320-H2AD but my O-320-E2D ran fine at 25 LOP (lean of peak). Any more and the engine roughness became a problem. So yes it ran LOP, but no it would not run 50 LOP nor would it run WOT (wide open throttle) LOP. Not a problem at the power settings I used.

    1. Why do you want to run lean of peak?

    2. What power settings do you want to run at?

    3. Do you have an engine analyzer with EGT and Fuel Flow?

    4. Do you have the Lycoming O-320-H2AD Operator's Manual?
    Last edited by ahramin; 09-17-2020 at 04:47 PM.

  3. #3
    FlyingRon's Avatar
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    Possible. Certainly. Just pull the knob out.

    Is it possible to run it effectively lean of peak. The problem is that on a non-injected engine, its hard to get all the cylinders running at reasonable mixtures on the LOP side. Some will be too rich, some too lean. If you get them all LOP, then some may be starting to misfire (not dangerous to the engine but not efficient) the poster above notes.

  4. #4

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    O-320 LOP running

    Quote Originally Posted by exftrplt View Post
    Is it possible to run a Lycoming 0320 H2AD - carbureted - lean of peak? If yes how?
    I ran my O320 in my Symphony (D-EMIC) very LOP during 5 yrs and strictly using Mogas. At annuals, the engine looked like brand new. The Symphony (a certified copy of the Glastar), leaned easily up to minus 150 rpm vs no leaning at the same throttle setting. It had a fixed prop. Calculated power was about 50-55% (80 HP and 20 ltrs/hr). Without any hiccups or rough running I was able to lean to minus 300 RPM, but it was difficult to adjust (small changes in mixture or throttle would result in large swings of RPM, so I never flew at such extreme settings.
    Now I have a very well instrumented O-320 E3D in my RV9, registration PH-RVN. The RV9 has a 3-bladed vari-pitch MT prop. So now I can really play around.
    HARD FACTS on long trips: 1830 RPM, 21 MAP, leaned to 18.2 ltrs/hr resulting in 42% power and 128 kts avrge speed. Very little noise in- and out-side, very gentle running of the engine, all temperatures go down: oil 82 degrees C, highest CHT 173 c, highest EGT 753 C. Mind you: EGT is unimportant; CHT is the one to watch. At such low power settings you can do no harm to the engine, no matter what you do (read Mike Bush: Engines) and many other writers. With the RV9 136 ltrs fuel tank, I can therefore fly during 7.5 hrs no reserve; I use 1 hr reserve it is still 6.5 hrs and a distance of well over 800 nm (plus 1 hr reserve). For large non-stop distances (example Ireland to Iceland), I start-off with 100 KIAS, 1810 RPM, 15.5 MAP and a consumption of 11 ltrs/hr, good for 12 hr (no reserve) and a distance of 1200 nm (no reserve). However, when I see that I can easily make it (winds may change quickly, so I start slowly and I can divert to the Faroe Islands if necessary), I'll increase speed to the numbers above: 128 KIAS etc. When the engine runs that slow, it sounds like fully at home. Coming from 2500 RPM for the climb, it feels like the engine is completely dying; I can actually see the prop turn.
    I know that I am extreme and many instructors from the old school have predicted I would ruin my engine, blow it up, etc. It is now my second airplane and 6 years that I lean the heck out of it combined with very low RPM's and relatively high MAP values (a difference of 6 maximum; ex. 18oo RPM and 24 MAP). Both O-320's seem to like it. No deposits whatsoever, completely clean exhaust,... Of course running such low RPM and, low CHT's, little fuel, every drop is fully burned, so there is nothing left as deposit of any kind; no dirty belly, very little engine wear. What's wrong with that?
    One important note about Mogas: here in the Netherlands all Mogas fuel pumps for aviation contain zero alcohol guaranteed, contain 98% octane and are tested every day - I never sump any fuel for testing; nobody does. Additionally the cost is 2/3rd of AVGAS 100LL , but still €1.80/ltr - Avgas is €2.80/ltr.
    So go ahead and lean the heck out of it; again at low power settings 50% or less, you cannot do any harm whatsoever. So where's the problem?
    And oh yeah, both O-320's are carburetted; both have about 700 hrs total (still the original plugs)
    Last edited by belgianbuzzer; 09-18-2020 at 08:05 AM.

  5. #5

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    Thanks to all. I conclude that I need more than just one CHT and one EGT to do this. Once again, thanks for you inputs.

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