Register

If this is your first visit, please click the Sign Up now button to begin the process of creating your account so you can begin posting on our forums! The Sign Up process will only take up about a minute of two of your time.

Results 1 to 5 of 5

  1. #1
    SpinnerRow's Avatar
    Join Date
    Oct 2008
    Location
    Flower Mound, TX
    Posts
    1,371
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    OS 75AX on a MACS 1260 Pipe

    Stock muffler and an APC 13x6 Sport was 11,800 and with the pipe I was able to get it to 12,900. Stick a 1/2" piece back in and I can run a 13x8 at 12,000. Throttle response with the 13x6 is sick! This is going on a 6.5lb Rookie which has a 59" slightly swept wing. Should be a fun combo. I need to get a 12x8 APC and try that but I had a limited number of props with me today since I wasn't sure what this thing would like.

    5% Ritch's Brew with 22% oil (11/11) and it is 86 degrees here in the Dallas area.

    Is 12,900 decent RPM for this motor or does this thing like more RPMs? The size of the carb suggests this is a lower RPM torquer but I'm just guessing.
    \"Hey!!! That tree was NOT there when I took off!!\"

  2. #2

    Join Date
    Nov 2003
    Location
    Auckland, NEW ZEALAND
    Posts
    1,324
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: OS 75AX on a MACS 1260 Pipe


    ORIGINAL: SpinnerRow

    Stock muffler and an APC 13x6 Sport was 11,800 and with the pipe I was able to get it to 12,900. Stick a 1/2'' piece back in and I can run a 13x8 at 12,000. Throttle response with the 13x6 is sick! This is going on a 6.5lb Rookie which has a 59'' slightly swept wing. Should be a fun combo. I need to get a 12x8 APC and try that but I had a limited number of props with me today since I wasn't sure what this thing would like.

    5% Ritch's Brew with 22% oil (11/11) and it is 86 degrees here in the Dallas area.

    Is 12,900 decent RPM for this motor or does this thing like more RPMs? The size of the carb suggests this is a lower RPM torquer but I'm just guessing.

    Those numbers look impressive. Do post your numbers on the APC 12x8 - for comparison, my Jett .90L with Jettstream muffler gets about 13K with the 12x8.

    Here's a tip - for each of your runs for each prop/pipe length combo, use Pe Reivers' spreadsheet to calculate the horsepower you are getting. Plot those on a graph and you'll see where the sweet spot is rpm wise. We did this with an MVVS .77 and found that it was happiest piped to do between 10,500 and 12,000 rpm. Anywhere in this band, we could pipe the engine to get a little over 1.9 HP calculated.

  3. #3
    SpinnerRow's Avatar
    Join Date
    Oct 2008
    Location
    Flower Mound, TX
    Posts
    1,371
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: OS 75AX on a MACS 1260 Pipe

    ORIGINAL: Harry Lagman
    Those numbers look impressive. Do post your numbers on the APC 12x8 - for comparison, my Jett .90L with Jettstream muffler gets about 13K with the 12x8.

    Here's a tip - for each of your runs for each prop/pipe length combo, use Pe Reivers' spreadsheet to calculate the horsepower you are getting. Plot those on a graph and you'll see where the sweet spot is rpm wise. We did this with an MVVS .77 and found that it was happiest piped to do between 10,500 and 12,000 rpm. Anywhere in this band, we could pipe the engine to get a little over 1.9 HP calculated.
    Weather was warmer and may more humid when I ran this test.

    APC 12x8 and 12x7 got 12,600. Pipe is too long for these props. It would probably spin up a little more if I cut more off the header. Debating if I want to do that or not.
    \"Hey!!! That tree was NOT there when I took off!!\"

  4. #4
    SpinnerRow's Avatar
    Join Date
    Oct 2008
    Location
    Flower Mound, TX
    Posts
    1,371
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: OS 75AX on a MACS 1260 Pipe

    Cut some more off the header. I'm in the 13,100 range on a 13x6. 12x8 is 12,700 and the 12x7 is about the same as the 13x6.

    Video of the 13x6 APC. Hard to be dissatisfied with this.
    \"Hey!!! That tree was NOT there when I took off!!\"

  5. #5
    SpinnerRow's Avatar
    Join Date
    Oct 2008
    Location
    Flower Mound, TX
    Posts
    1,371
    Gallery
    My Gallery
    Models
    My Models
    Ratings
    My Feedback

    RE: OS 75AX on a MACS 1260 Pipe

    Can a moderator move this to the Tachometer Forum? That's where I wanted this one to go in the first place.
    \"Hey!!! That tree was NOT there when I took off!!\"


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
All times are GMT -6. The time now is 11:18 PM.

SEO by vBSEO 3.6.1 ©2011, Crawlability, Inc.