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OS 91 FX Tach readings

Old 07-03-2004, 10:26 AM
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wood
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Default OS 91 FX Tach readings

If you have any Tachometer readings for your OS 91 FX please post them here.
Old 07-03-2004, 11:20 AM
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bentgear
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Default RE: OS 91 FX Tach readings

Have you tried hitting the search button? Lots of info out there.

Ed M.
Old 07-04-2004, 09:58 AM
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wood
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Default RE: OS 91 FX Tach readings

yes, and I just asked you a question in another thread. But since this is in the Tach Readings area, I thought I would ask here too. I am trying to figure out how a OS 91 FX compares to a YS 91 FZ on a 3d type prop like the APC 16-4W. Can you post what you are experiencing?

Thanks,

WOOD
Old 07-04-2004, 10:44 AM
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Hercmate
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Default RE: OS 91 FX Tach readings

Wood,

that is so strange! I just came on here to post EXACTLY what you just did! I want to see if its worth changing my YS91 for an OS91 on that exact prop.

How spooky

Andy
Old 07-07-2004, 01:53 PM
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malcolmm
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Default RE: OS 91 FX Tach readings

APC 15x4, 10% cool power - 10,500 peak, I richen it up to around 10,300 for flying.

I would be interested to know how this compares to a YS 110. I am looking at 90 to 120 size 3D planes like the Funtana 90 and Extreme Flight 68" Yak. The OS 91 FX would be a bit marginal in these planes, I would like to know how much extra thrust I would get out of the YS 110 - running the same % nitro.
Old 07-07-2004, 09:52 PM
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wood
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Default RE: OS 91 FX Tach readings

Thanks, for the info, I would like to know as well.
Old 07-08-2004, 09:10 AM
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Default RE: OS 91 FX Tach readings

The OS 91FX and the Magnum 91XLS are virtually identical in performance, and my Magnum on a Performance Specialties Ultrathrust muffler turns an APC 16x4W at 10500 on 10% Omega. With the stock muffler, it only turns around 9200.
Old 07-10-2004, 05:20 PM
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basmntdweller
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Default RE: OS 91 FX Tach readings

Something must be wrong with my 91FX! CP 15% only gets me 8800 on a Pro-Zinger 15-6. I have a Pro-Zinger 15-4 to try but I needed another washer between the prop and stock washer. The nut ran out of threads before it would tighten up on the prop. I bought an Ultrathrust muffler for it but haven't used it yet. I need to get mine up to the performance you guys are getting before I swap mufflers. Maybe it's due for a piston ring. Compression is excellent and it starts and runs fine, just not near the power you guys are getting. I'm pretty sure it used to turn over 10000 with the Pro-Zinger 15-6 last season.
Matt
Old 07-12-2004, 01:56 PM
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jharkin
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Default RE: OS 91 FX Tach readings

12x8 APC - 11,700 peak, idle around 2200-2300 after a gallon of break in.
- stock muffler, powermaster 15%, OS #8 plug, 75F and humid at around 500ft ASL.

This motor is the older style of remote needle and I do get some bubles, but it only seems to affect the midrange, idle and full blast are rock stable. I'm going to try the perry remote needle to fix the midrange.
Old 07-20-2004, 01:32 PM
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STG
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Default RE: OS 91 FX Tach readings

10,400 15x6 apc with baffle removed.

11,300 15 x6 apc and ultrathrust.

Moves a 10 pound plane around with ease--pull out is very good.

15%cool power.
Old 05-23-2006, 03:23 PM
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MattyC-130
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Default RE: OS 91 FX Tach readings

12x8 APC 15% nitro os#8 plug, 12k with stock muffler(baffle removed), 13k with Ultra Thrust muffler.
Old 06-05-2006, 07:09 AM
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Default RE: OS 91 FX Tach readings

My tower .75 turns a APC 12/8 @ 11,400 richened for flight running WC 10% with a Slimline pitts muffler. Maybe I will not put the FX.91 in that plane.
Old 07-06-2006, 05:27 PM
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Flyer95
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Default RE: OS 91 FX Tach readings

I have about 10 tanks through my OS91FX now and the prop has been the APC 12x14 from the first start. Muffler is the stock and it turns that prop +9000rpm. I am gonna tach it later again when a have leaned the high speed needle more. I use this engine on a speed plane of 1200mm (47inches) wingspann and it goes pretty fast end very quiet. This engine runs very nice and reliable and had only one tank on the ground and the other nine in the air I use OS8 plug and 10% nitro.
Old 04-09-2008, 07:48 AM
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Lutzifer
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Default RE: OS 91 FX Tach readings

My OS 91FX tachs at 9800 with a 13x10. I use for speed as well in my Minnow. I was thinking of trying a 12x10 out, but after the previous post i might try that 12x14 as well! Question, is there any guideline as to how much an engine will unload when flying, or how close to the max rpm specs of an engine you should be when taching on the ground?
Old 10-06-2009, 08:01 PM
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Default RE: OS 91 FX Tach readings

HI CORRECT ME if i am wrong -but OS recommends running this engine at 11,500 rpms-to be in the correct power band for this engine-which no one here is doing i see high 9's mid 10' s and even 13'000i am running a 13/7 APC at 12,100 (stock muffler ) and came here to get closer to 11,500 on an APC-had a 14/6 APC on my 60 size ULTRASPORT-it ran bad at mid range which is were i normally fly most ( ran at 11,100 )-but low end was way to rich at that time -and the engine was not yet broken inso it ran poorly with some vibrationhave to try that again with the needle valves set up much more correctly now-is anybody running this engine in the 11,500 range on an APCif so which prop THANKS TONY
Old 10-06-2009, 11:00 PM
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jamesc43
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Default RE: OS 91 FX Tach readings

I got my OS 91 FX in a H9 Pulse XT 60. I bought it used with a MAS 13X* prop. I put a tach on it a couple weekends ago. I was
getting around 10500. I tried MAS 14X8 prop not to long after I got the plane. The plane spends most of the time around half throttle so I really don't see how making sure it hits the power band is so important.
I also had a YS 91 AC in a WM P51. I oringally had a MAS 15X8 prop to keep it under 9000. I eventually put a MAS 14X8 prop on it and I am getting around 9200 RPM sitting on the ground. I am sort of worried that during high rpm runs that the engine might overspeed and brake. Anyway, the plane wrecked and so the engine is sitting on the test stand at the moment. I am thinking avbout putting it in a Sportsman Aviation Waco 60.
Old 01-03-2010, 01:29 PM
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Default RE: OS 91 FX Tach readings

hi my OS 91 FX started to run very different than it has in the pastafter hours of fiddling saw a lot of air bubbles only- mid rangechanged the needle valve '' O'' ring and all got back to normal the plane and engine are 10 years old my pattern flying buddy told me he changes his nv ''O'' ring once a year as normal maintanence-i would like to pass this info on as this is often overlooked and can save us a lot of time fiddling at the fieldnot to mention dead sticks and engine damage from air leaks
i was running my 60 ULTRASPORT on an APC 13/7 @ 12,100 RPM i went to a 13/6 now at 13,300 RPM (top end RPM readings ) as i run my engine mostly at mid rangewere it sound richer than i would like it to (just do not like the sound it makes at midrange ) thought that more RPMS at midrange would help consume more of the fuel there it worked-like it better
when using the pinch fuel line -method to set the top end nvyou need to pinch the fuel line -just before the carb-with a remote nvyou will get incorrect feed back if you pinch before the remote nv-my low end when pinched has about a 3 second run up when it is set as it s/bthis is fresh in my mind as this just happened this week
i need to try the ultratrust muffler to see if it helps me enjoy the sound of the engine moreas i said i really do not like the way it sounds nowthe stock muffler always seemed to have a strange harmonic-as strange as the engine has soundednever once has it stopped running on me
another thing that is odd to me are the great number of different props that are posted in threads that this engine will run on from my 13/6 to a 16/4 but i do understand you prop the plane not the engine for performancevertical performance in a given airplane being the guage we measure performance by
my ULTRASPORT with the 91 FX flys and tracks on railsmore power than i could need-a super great flyer that gets its share of attention when i fly herejust got to get here to sound betteras i am very motivated to fly the planes i own that sound awesome in the airthats the rush for meOH WELL-working on that ENJOY REGARDS TONY

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