Zodrak

Hi,

I have a 3W 55 US engine with a supersonic pitts style muffler and a 3W 23x8 prop . The engine is mounted inverted and I have a 3W tank and the vent nipple has a tube that goes inside the fuse.
When I fly on knife edge with the carburetor up the engine reduce rpm and almost die. This phenomenon apears only with the throttle lower than 40-50 % . On high rpm it works fine. But on 3D manouvers the engine it not responding right .. rolling hariers… for example.. every time that the carburator goes up.. the engine loose rpm. I've check and change the tank.. over and over again.. no results.

Last weekend I leaned the low needle and the problem seems to reduce a little .. it only reduce rpm if the throttle is about 30% or less., but the down side is that is dificult to start the engine when is cold.

PLEASE help …!!! What is the problem ? I know in theory that the engine should run in any position because the carburator has a pump in it…

On the ground I tach 6400 rpm and I have a steady idle .. and it works greate in any position. The engine has about 30-40 litters of gas thru it and I use sintetic oil 1:40.

I wrote the problem to 3W suport and I got no answer…

How long should be the tube from vent nipple to the fuse ?

I have 2 more 3W engine 28 cc … should I espect the same problem ? Or is because the side carburator ?

Thanks !

skiman762

My guess wouldl be it has something to do with the way the air get into the cowl in the knifedge position it may be taking away or giving the carb more air messing up the mixture.
lots of airflow changes around the cowl happen in aerobatic/3D flight
Try flying it without the cowl and see if you still have the problem

Zodrak

With or without the cowl is the same thing ..i guess.,.. because the carburator is outside the cowl. This is the second cowl. In the first cowl I have almost full opening around the motor and same problem...

Zodrak

Anyone ? I have this plane and engine from almost a year .. the guys on 3W dosen't bother to respond to my problem...

Any ideea where is my problem ?

Steve

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One thing you can try is taking the vent tube off. Looks like you may not need it. I'd also look at the carb crap trap inside the carb. If it has a restriction, you will be running the low needle out much more than its supposed to be and that could be affecting your mid range. Clean the carb good and see if that helps. Your low needle should not be out more than 1 and 1/4 turns open and are usually around 1 turn open. If you are more, than I'd clean the carb and see what happens.