Light-Sport Aircraft Yahoo group Re: Can cruising the Rotax 912 a bit below 5000 RPM actually INCREA >

> Posted by: "pwrsport@ix.netcom.com" pwrsport@ix.netcom.com
>
> I have been using Ethanol fuels (10%) in our 912’s here in
> the phoenix metro area for about fifteen years or more with zero
> problems. Also zero problems with water in the fuel. The Rotax
> engine is design to run around 5300 rpms all day, every day and
> could care less. Rotax 912 engines obtain volumetric efficiency
> at high rpms and were designed so. Lugging the engine at low
> rpms is not the best trying to save it? Those flying 50 to 100
> hrs a year may die before the engine does. Keep the r’s up
> in continuous cruise and watch the temps, high oil temp is the
> enemy.
> Ed Snyder

Lugging:
when an internal combustion engine is run at overly low RPMs
for the load being applied to it,
potentially damaging the engine in the process.

Yes Ed, nobody is recommending "lugging the engine".
An example of that would be if a pilot had an in-flight adjustable prop,
and while flying with almost full throttle, he then dialled in
more pitch causing the RPMs to reduce, eg down to 4500.

This is completely different to the situation I had in mind, and which
would apply to all Sport/LSA craft (no in-flight adjustable props)
which is where the pilot no longer needs full power from the engine,
and reduces the throttle setting until the RPMs are (say) 4500.

If the engine was providing 80 HP at 5500, then (using a rule of thumb)
slacking off the throttle until engine revs are 4500 would be using
about 4500 cubed over 5500 cubed times 80HP.
IE; about 44HP.

Mike

(the above rule of thumb is more accurate if the airspeeds are similar)
(eg;
 climbing at 70 mph with 5500, and then cruising at 70 mph with 4500)

.

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