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

[John Pavlick]

Yup, I agree. Replace the rear bearing before you fire the engine for the first time and you're good to go. Also, the front bearing in the 120 is a double sealed type (like the 140 F.I. rear bearing) whereas the 91 has a shielded bearing. In my experience the double sealed bearings last much longer so if you put one new bearing in the 120 you should have NO bearing issues for a long time.
   
  John Pavlick

michael s harrison <drmikedds at sbcglobal.net> wrote:
                Cant get too much power.  Do the 120.  Also, consider replacing the bearing with the OS1.4 efi bearing and the engine will run great forever.
   
      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 12:24 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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