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

[John Pavlick]

Stock muffler works fine with a 14x8 prop on a Venus 2. RPM is in the 8-9K range on 15%. I'm about to try an Aeroslave pipe. That should give me a few more prop choices as well as some added grunt. We'll see. This is a nice motor. Quiet and VERY easy to handle. I haven't touched either needle since it broke in.

  John Pavlick
  
Bob Richards <bob at toprudder.com> wrote:
            What are you guys using for muffler/pipe on the 120AX?
   
  What you say makes sense if you look at ALL the numbers. The 2.8hp of the .91 is at 15k rpm, while the 1.20 is 3.1hp @ 9k rpm.  The hp of the .91 will probably be much less at a pattern useable rpm, while the rated rpm of the 1.20 is very close to a useable rpm figure.
   
  Bob R

--- On Thu, 6/26/08, J N Hiller <jnhiller at earthlink.net> wrote:

  From: J N Hiller <jnhiller at earthlink.net>
Subject: Re: [NSRCA-discussion] OS 91FX or 120 AX for Focus sport
To: "General pattern discussion" <nsrca-discussion at lists.nsrca.org>
Date: Thursday, June 26, 2008, 4:02 PM

              I recommend the 1.20 AX. It will turn a bigger prop, which offers a more efficient HP – Thrust conversion. I am flying advanced with a 9+lb airplane powered with the 1.20 AX and a 16-10 APC. I am getting away with the 16-10 but I feel I am pushing the upper limit. It would probably be more comfortable with a 15-10 or 16-8. It is probably more power than needed in lower classes but throttle management is one of the things we need to learn and the sooner the better, besides the extra power will be most welcome in adverse weather conditions.
  Jim Hiller  
   
    
    
           
    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
   



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