A more effective way is to control the pressure in the float bowl (via the
float breather). It is only this pressure which drives fuel through the
carburettor jets; so if you can control it you can control mixture strength.
Duncan McFadyean
-----Original Message-----
From: JohnJMoran@aol.com <JohnJMoran@aol.com>
Date: Thursday, August 19, 1999 2:41 PM
Subject: Re: Flying: Fuel consumption with Rotax 912.
>Has anyone tried leaning the Rotax' mixture at altitude by introducing a
>controlable air leak (via a needle valve) through the fitting provided for
>connection of a manifold pressure gauge? Manifold air leaks generally
cause
>undesirable leaning -- this would be an attempt to use a controlled
manifold
>air leak to achieve desired leaning.
>
>Unfortunately, this crude approach would be sensitive to power setting:
>reducing power with the leak open would (I think) cause the mixture to go
>leaner. The pilot should close the valve before changing power to avoid
>over-leaning. But it might, in careful concert with EGT readings, allow
>better efficiency during stable cruise at altitude. With the danger, of
>course, of the engine quitting or being damaged if the pilot changes power
>setting without closing the leak. As with early turbochargers, the pilot
>could damage the engine through unconsidered use...
>
>
>John A044 Newtown, CT
>
>
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