Rotax 912UL airbox or not?

by Przemysław Wiśniewski in 912 / 914 Technical Questions 8 years ago

HI. I want to buy water carburetors heaters but there is also option to use oryginal airbox for my 912UL
Question is, what gives airbox? Ok, carburetors heating like on cessnas etc but there is something else?
More power, performance etc?

Re: Rotax 912UL airbox or not?

by Roger Lee » 8 years ago

Roger Lee

131 5.38k 5.44k

They are better tuned for the engine and setup for proper cool air flow to the carbs. Using air filters on each carb under the cowl isn't a good way to go. The guys that have air filters under the cowl attached right to the carbs are flying in carb heat all the time. It makes for a rich fuel mixture. Cool or cold (depending on your definition) dry air for combustion would be better.
I too like the hot water carb heat option. The Rotax air box has an inlet to attach tubing that comes off the muffler for carb heat when needed.

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

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Re: Rotax 912UL airbox or not?

by Peter Kl. » 8 years ago

Peter Kl.

7 230 382

Provided the air box is fed with cool air from the outside rather that from underneath the cowling (have seen some weird installations) there is a chance to get a little more power from that. This effect is maximized when flying full throttle. Since (I guess) none of us is doing this "all the time" the effect on power will be limited. However, if it is not the performance on full power it may lead to a slightly reduced fuel consumption. At the end of the day you may as well save the dosh and keep flying without an airbox.
To me it seems better to use the water based carb heat against carb icing than feeding warm air through the carb. Both ways work, but personally I do favor the first one. Besides, the temp underneath the cowling is not as high as one would think during flight which limits both the potential power gain and the carb heating function.
Regards
Peter

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