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Anyone got readings OS Fx 91?

Old 02-12-2006, 08:05 AM
  #26  
RCflying
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Default RE: Anyone got readings OS Fx 91?

Ultrathrust Muffler,
Tower Power 15%(3rd 12oz tank),
14X7 Top Flite Power Point 2 blade prop,
700 ft, 40 degrees,
12,000 RPM,
Thrust HP Calculator indicates 3.3 HP and 15.66 lbs of thrust.
I have two, one for an World Models Midget Mustang and one for an AKM Su-27 Flanker.
Mike
Old 02-22-2006, 11:04 AM
  #27  
Kostas1
 
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Default RE: Anyone got readings OS Fx 91?

Two-three weeks ago i received my OS 91 FX with the upgrades in the needle and backplate installed.
It is installed in my Hangar 9 Corsair.
I will break-it in in a couple of days so i will let you know.
Also i will start with an APC 13x8 for the 2-3first tanks and then i will go with an APC 14x6.
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Old 07-24-2006, 07:23 PM
  #28  
Bill Yonescu
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Default RE: Anyone got readings OS Fx 91?

Just tried the FX-91 with 4 different 16x6 props. All with 15% Power Master and standard muffler. All are peak RPM (I wouldn't fly at this). Trust is static within minutes of each other.

MA "K" Series - 8850 - 11 lbs 12 ozs.
MA Classic - 8600 - 10 lbs 15 ozs
MA Scimitar - 8500 - 11 lbs 0 ozs
APC - 8600 - 11 lbs 5 ozs ( this may be low - will retest - think it s/b about the same as the "k" in RPM & Thrust))
MA "K" Series - 8850 - 11 lbs 12 ozs. ( repeated test)

This FX-91 is brand new - looks and runs great. Haven't tried any other props.

Bill
Old 09-12-2006, 02:48 PM
  #29  
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Default RE: Anyone got readings OS Fx 91?

OS-91 FX with pipe (Merker) on 18% synthetic/castor mix oil, 5% nitro:
APC 15-6 at 9400 rpm, 93 Db at 3 meters; great flying, but a little noisy!
APC 14-8 at 9100 rpm, 91 Db. Good flying
APC 14-10 at 8300 rpm, 89 Db at 3 meters; good for pattern flying, but "feels" slow (which it isn't)
Old 09-17-2006, 03:10 PM
  #30  
asmund
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Default RE: Anyone got readings OS Fx 91?

apc 14-10. 9300 rpm. apc 14-6 11300 rpm. on tower 75 muffler and os 60L helicarb[8D]
Old 09-17-2006, 05:21 PM
  #31  
Flyer95
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Default RE: Anyone got readings OS Fx 91?

APC 12x14 and four chamber quiet pipe turning @9700 static but unloads very nice airborned and pulls my plane like crazy[sm=wink_smile.gif]
Old 09-18-2006, 01:55 AM
  #32  
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Default RE: Anyone got readings OS Fx 91?

What should i expect with an MA 15x4 static?
I have installed my FX on my new UCD 46
Old 09-18-2006, 07:21 AM
  #33  
Bill Yonescu
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Default RE: Anyone got readings OS Fx 91?

Since wagen017 got 9400 with the 15x6 MA you should expect at least (according to ThrustHP) about 10800. - Bill
Old 09-18-2006, 09:43 AM
  #34  
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Default RE: Anyone got readings OS Fx 91?

I think you should expect 10500-11000rpm static.
Old 12-15-2006, 12:08 PM
  #35  
Fuelman
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Default RE: Anyone got readings OS Fx 91?

Old well used 91FX (only one that ever ran good for me). Engine is on a Bruce Tharp Delta Vortex and it goes like a scalded cat with the 14x8

APC 14x8, 15% fuel, stock exhaust: 10410 rpms
APC 14x8, 20% fuel, stock exhaust: 10530 rpms
Old 09-21-2007, 08:44 AM
  #36  
WMB
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Default RE: Anyone got readings OS Fx 91?

How does this engine run inverted? I know fuel tank position is important. Will it idle ok is the big question. I've had/have 2 4 strokes and 1 2 stroke that run great inverted. Had bad luck with another 2 stroke inverted. Thanks, MikeB
Old 11-27-2008, 07:07 AM
  #37  
mfuess
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Default RE: Anyone got readings OS Fx 91?


ORIGINAL: africanmike

They don't like to run much above 10000 R.P.M. so prop accordingly. An A.P.C. 15x8 will turn about 8900 and a master airscrew 14x9 three blade , about 9600. The MA 14x9 can be difficult to find Though and a 14x7 three blader will churn about 10000 R.P.M.
I have to disagree with you on this. I have an OS 91FX on a pylon plane and it turns an APC 12x8 prop at 13,500 RPM on the ground, and 14,700 in the air. My engine runs perfectly every time, every flight.
Old 12-06-2008, 03:08 AM
  #38  
DarZeelon
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Default RE: Anyone got readings OS Fx 91?


ORIGINAL: mfuess

I have to disagree with you on this. I have an OS 91FX on a pylon plane and it turns an APC 12x8 prop at 13,500 RPM on the ground, and 14,700 in the air. My engine runs perfectly every time, every flight.
MFuess,


I agree with you, as long as a good, high-performance aftermarket exhaust, like the Nelson UltraThrust , or the JettStream is installed, along with a suitable.

With the original muffler with the baffle in place, this engine will be happier doing 10-11K.
Old 02-15-2009, 05:38 PM
  #39  
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Default RE: Anyone got readings OS Fx 91?

I'm wondering if I can change this thread just a bit.
I have a problem and would like some assistance. After a bit I'll post my rpm readings, but since I haven't tach'd my 91FX in quite a while, that'll have to wait.
Here's my problem.
I have a Midwest Little Cap 232 that I have my OS 91FX pulling it around. I built it several years ago and it came out a bit heavy - maybe 8.5#.
I started powering it with a TT91, but wasn't happy with it - kept overheating - or it seemed like that was the problem. So I swapped it out for the OS91FX.
Seems like I continue to have overheating problems, or at least it'll pull like crazy for about 5 minutes, then I'm into a dead stick.
I'm currently running Wildcat 18/20 fuel, propped with an APC 14x6, which broke on a dead stick landing - replaced it with a 14 x 7 - another dead stick. Replaced it with a 13x6 MAS and same result.
The engine is cowled in, and has an air dam in front to push incoming air to the head, and has a big outlet area for exit heat. The cowl has a large cutout where I previously had the 4-stroke engine in.
I'm wondering if that open area is just allowing too much air to escape from around the head. Or should I just be using cooler (lower nitro) fuel or maybe a hotter plug?
Any suggestions? Thoughts???
Thx all
Pete
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Old 02-15-2009, 09:19 PM
  #40  
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Default RE: Anyone got readings OS Fx 91?

Pete Sounds like you have had similar problems with both engines. I would make sure there is not a problem with the fuel tank and associated fuel lines. Seems like both engines are having a similar problem, so it's time to look at issues that could be affecting both engines. From what you said it doesn't sound like air inlet and outlet is the problem for cooling. If that is true then something else is causing your engines to run hot and quit. How close to the engine is the fuel tank, and could it be mounted much lower than the center line of the engine ? Also is the tank wrapped in foam rubber or could the fuel be foaming due to vibration if it's not. I'd check out the tank real good if it was me.
Old 02-15-2009, 10:09 PM
  #41  
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Default RE: Anyone got readings OS Fx 91?

Good thoughts!
Maybe I'll just retank and put new fuel lines on it.
Project for this week!
Thanks for the suggestions.
Pete
Old 02-16-2009, 01:07 AM
  #42  
DarZeelon
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Default RE: Anyone got readings OS Fx 91?

Pete,


You may also want to do a search in the '[link=http://www.rcuniverse.com/forum/forumid_114/tt.htm]Glow Engines[/link]' forum, for threads that address exactly this issue.

Unlike some other things in life; engine cooling is not all about sizes and diameters... In fact, they have but little importance.


Having a large cooling air inlet and a three times larger exit, may not necessarily cool your cowled engine.

For a cowled engine to be properly cooled, it should be elaborately baffled, to cause the incoming air to flow snugly around the cylinder and especially around the head.
The cooling air must flow relatively slowly, between the cooling fins; not just around them. And then it must be extracted from the cowl.

Even if your model has a voluminous cowl, with a large entry (even directly in front of the cylinder) and a three times larger exit hole(s); what guarantees that the cooling air will not just flow directly from the entry to the exit; bypassing the engine altogether, or that the air will at all flow in the right direction (i.e. the pressure at the exit could be higher than at the entry)???

Go to your local airport and take a look at some light, piston-engine planes, to see the elaborate baffling around the engine... It might initially appear to mask-off the cylinders altogether...


Learn and apply!

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