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  • Re: removal of airbox cause significant oiltemp inc

    by » 11 years ago


    Ok Roger ..I hear you.. I will pneumatically sync my carbs forthwith.
    In the mean time I have re installed my air box and .. problem solved..did an hour flight up to 4000' and temps were back to their old self of very cool.
    SO ..out of this experience I must deduce that the 'optional' airbox.. it is actually essential on most LSA's given that my installation is pretty much the average or norm tractor config.

    Incidentally, I would estimate the temps are down by 20 deg C both CHT and oil temp. I would never have expected that.

  • Re: removal of airbox cause significant oiltemp inc

    by » 11 years ago


    Hi Dave,

    Glad to hear it. I always tell people not to mess with air flows and fuel flows. Rotax has this setup in balance and doing something as innocuous as turning the carb more sideways verses straight up can change air flow enough to change temps. When making a change on an engine it is imperative to know why a company did something for the reason they did. It usually isn't a random decision and making one change can have an affect on 2-3 other items.
    I have seen a Bing 94 carb on a Jabiru and when it was turned you could manipulate the temps and all by air flow. This is actually a recommended practice for that engine. (It is not recommended for the Rotax)

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


  • Re: removal of airbox cause significant oiltemp inc

    by » 11 years ago


    SO ..out of this experience I must deduce that the 'optional' airbox.. it is actually essential on most LSA's given that my installation is pretty much the average or norm tractor config.


    The airbox is not essential, but if installed the carburetor jet needle clip position or main jet size may be different to the jetting on the same engine installation without the tuned airbox. By removing the airbox, it sounds like you might have affected your mixture. You can certainly remove your airbox but you will then need to make a change to the jetting on your carbs.

    This point is addressed in a note on the US distributor's web site. "Important Note: If an air intake box of a different design is used, or no air intake box is used at all, changes in carburetor settings may be required. In addition, correct carburetor settings must be confirmed by a CO measurement carried out on each cylinder using the same procedure as set out for the ROTAX 914. (see Rotax Service Instruction SI-07-1997)"

  • Re: removal of airbox cause significant oiltemp inc

    by » 11 years ago


    Mike .. thanks for that. I stand corrected.
    Dave

  • Re: removal of airbox cause significant oiltemp inc

    by » 11 years ago


    You're welcome. You can buy the manual for the Bing 64 carbs on your engine for $11.00 shipped from the Bing Agency. The manual contains the information you will need to rejet your carbs. You may need to buy new needle jets. Your aircraft's manufacturer can probably tell you which needle jets were installed in your carbs at the factory (and also the jet needle clip position). If not, the needle jets have identifying marks which allow you to determine their Rotax part number.

    And just to cover all the bases, the airflow through your cowl may be sufficiently different without the airbox that the oil cooler and coolant radiator are seeing less airflow.

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