[NSRCA-discussion] OS 91FX or 120 AX for Focus sport

[Archie Stafford]

I would definitely go with the 120AX out of these 2.  It really will make a
difference.  Those may be the posted numbers, but I own a 120AX and it has a
LOT more power with the right prop than the .91 does.  Also, the Focus is a
pretty good size plane.  

 

Arch

 

  _____  

From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Shoval
Aviv-BAS036
Sent: Thursday, June 26, 2008 8:24 PM
To: nsrca-discussion at lists.nsrca.org
Subject: [NSRCA-discussion] OS 91FX or 120 AX for Focus sport

 

Hi All,

I'm fairly new to pattern flying. I'm considering to buy the Focus sport and
want to "keep it simple" with the engine. I know the Focus was design for YS
110 but for cost/ simplicity reasons i am considering the OS 91 FX or the OS
120 AX. In the OS web site they claim that the 120AX is 20% more power but
when I compare efficiency it looks like the 91FX wins. Its 6% more efficient
in power to Wight and 16% more in power to displacement. Am I missing
something? Practical RPM misleading numbers? What would be your
recommendation?

 


 

120AX

91FX


Displacement (Cu in)

1.2

0.91


Weight (gr)

650

550


Output (BHP at RPM)

3.1 at 9000

2.8 at 15,000


Cost

250

200


 

 

 


output/ weight

0.004769

0.005090909


Output/ displacement

2.583333

3.076923077

 

 

Best Regards,

Aviv

 

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