YS160DZ loads up in vert
 

Similar question to byoung's recent question, but a bit different.

I load up at the top of verticals when at WOT. Flying level at mid throttle, ready to do 1/2 square loop, pull to vertical and apply WOT. Transision to WOT is typical YS, ie great. However, by the time I'm ready to push or pull to level at the top of the vertical leg, the engine has started to load up, RPM drops, and there is a lot lot of smoke. It will clear out a about 2-3 seconds later at WOT after I pull to level at the top.

The problem seems most pronounced when I need WOT after the engine has been running in the midrange for a while. I have however noted the issue will occur in about any WOT vertical if I hold the vertical long enough. WOT in level or even 45's never seem to produce the issue, only verts. No other issues noted. Engine runs great otherwise. Idle and transition and WOT (not in vert) are fine.

Engine has about 15 gallons in it, using CoolPower 30% heli, APC 17x10 standard(not the narrow), OS F. Regulator never touched and is set as per factory, high needle set about 1-1/4 to 1-1/2. I have set the valves, but it was about 8 gallons ago. The engine did this from day one to a certian extent. The issuse is just more pronounced recently.

I would like some expert advice before I fiddle with it anymore. Suggestions? Thanks.

RE: YS160DZ loads up in vert
 

Weird!

Try a different prop size, maybe a little heavier.

RE: YS160DZ loads up in vert
 

Thank's Dave, you were right on. I checked, and I was turning the 17x10 well over 8,500 RPM. I could swear that it wasn't over 8,500 a few weeks ago with that prop, but the point is moot. I propped to APC 17x12, RPM dropped to 8,350, and my problem went away.

RE: YS160DZ loads up in vert
 

Dave guesses right!

Hasn't happened often lately.

Good Flying!

Dave