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

[Shoval Aviv-BAS036]

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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