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HomeAircraftHelicopterFuel-Helicopters New or Limited ActivityAvant › YS 91 ST gear ratio?
06-06-2009 03:58 AM  9 years agoPost 1
Heli Wiz

rrApprentice

Moravia,N.Y. U.S.A.

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Can anyone tell me what is the best gear ratio for the avant EFX? I'm running a YS ST 91 with a Curtis pipe. It currently has a 7.91 in it. Is that to much? Thank's Bill.

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06-06-2009 06:55 AM  9 years agoPost 2
Dood

rrProfessor

Wescanson

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You would be better off with 8.45:1 with the ST.

I don't see a reason why the 7.9 wouldn't work for you, you just may have to deal with a higher headspeed to get your engine RPM's up into the power band.

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06-06-2009 03:31 PM  9 years agoPost 3
Mike Wilson

rrVeteran

Toronto, Canada

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I agree with Dood. 8.45 with a headspeed of about 1850 to 1900 is optimal for the YS 91 ST. If you are running 7.9 you'll need to run a headspeed of about 1950 to get into the power band but you will probalby loose a bit of torque. The higher headspeed will make the machine a bit snapier but you will have the manage the collective a little bit better at that gear ratio.

....Mike

Teambob00

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06-09-2009 01:22 PM  9 years agoPost 4
Chopper

rrKey Veteran

Stow,Oh- oops, I mean St Louis, nope Stow again,

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I dissagree on the 8.45. If you can get the 8.18 gearing for the Avant, the ST runs great on that ratio. That is what I use. I run 8.25 on the Aurora and the Avant runs just as good or better with that ratio. In my opinion...

Paul Soha is a free agent now. Wow.

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06-09-2009 04:32 PM  9 years agoPost 5
Mike Wilson

rrVeteran

Toronto, Canada

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It really depends on your flying style and collective management. Best thing to do is experiment until you find what works for you.

....Mike

Teambob00

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06-22-2009 03:28 AM  9 years agoPost 6
CoronaL

rrKey Veteran

Winnebago IL

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~8.2 on my Rex700 and ST at 1950 or so was pretty darn good power with Hatori SB16fh. With a new outrage90 pipe or the RJX pipe, or SB19 maybe even better

Randy!!! I am the liquor

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