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

[Ihncheol Park]

Aviv,
Go with 120AX.  It has more power at lower RPM.  You can run 91FX at lower rpm, but setting isn't that easy.  
Even the new Aquila can be flown with 120AX.
Ihncheol


----- Original Message ----
From: Shoval Aviv-BAS036 <aviv at motorola.com>
To: nsrca-discussion at lists.nsrca.org
Sent: Thursday, June 26, 2008 12:24:19 PM
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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