bert-RCU

I own a new OS 91 FX ringed , I have a couple of questions :
1) Has anybody used this engine for 3D Flying ? , I d'ont know which is the best prop for this engine (My 3D plane is about 75 In span).
2) I found a cone baffle inside the muffler , can I remove for improving the performance ?
3) What you think about using nitro fule with ths engine ?.

THANK YOU!

Walt and Sage

I fly a ModelTech "FUN FLY 90" with an OS 91FX and it is a BLAST...

298 flights and going over 300 TODAY... GREAT PLANE & MOTOR...

If you remove the baffle you will need to install a stronger rod that
holds the muffler together or it will snap during flight..
I used 10/24 all thread rod with double nuts and lock tight
The OS 91FX has 2.8 hp and the size and weight of a 60..
I use 10% nitro fuel and runs just fine...

HAVE FUN...

EL TEMUCANO

SUPER TIGRE G90 APC 14/6 CA MODEL EPSILON

SUPER TIGRE G90 APC 14/6 SWALLOW EX 90

STG

My Feedback: (26)

Best props .91FX for a 8+ pound 3D plane are:

Ranked by spool up--

1) 15 x 6 Schimitar wood or Pro Zinger
2) 15 x6 APC
3) 16 x4w

Removing the baffle should give you another couple hundred RPM

Mine turned 10,300 with a 15 x6 apc and baffle removed on 15% cool power.--just enough to hold my 10 pound Spacewalker in a hover. Had no trouble with the muffler stud.

I like 15%, but will run good on 5-10% as well.

George E.

My Feedback: (16)

Remove the baffle in the muffler.

I have good luck with the 15x4W APC but never tried the 16x4W.

I run 15% nitro.

You can drill the muffler outlet to a larger diameter but it will be LOUD.

EXTRA ADDICT

My Feedback: (2)

Do you guys have any fuel delivery problems with the baffle removed? Do you have to run a pump with it like that? I have this motor in my Harrier 3D 90 with a 15X4W on it and I am wondering if there is much of a performance increase. It does graet but I would like a little more punch out of a hover.

bert-RCU

Thanks to everybody , your informations are very apreciated!

STG

My Feedback: (26)

If this is still not enough get the Ultra thrust muffler or Turbo Jet. The .91FX the Ultra Thrust would turn a 15 x6 apc 11,400 (10,300 stock muffler baffle removed) This was enough to give me confidence to hover the 10 pound space walker lower and still have power to pull out.

The Ultra Thrust is a little louder and I did notice an increase in fuel usage. Also, make sure if you order one you call and let them know what your application is (what prop and motor you are running so you get the right one.)

wahlrite

I run a 13 x 8 APC, 3% nitro , 17% oil , 80% Methonol on a .60 ultra stick, my os .90 will turn 12,500 rpm with the noise reducing disk removed from the expansion chamber and the exhaust outlet drilled out as big as i could with out hurting it.
Im at 2700 feet above sea level 100 deg. F 5% Hum. 15% DP. and about the same numbers with a MAC pipe.
the manual states that it will make 2.8 BHp @ 15,000, I personally take that number 15,000 and pick a prop so the RPM will hit 75 to 80% of that RPM ( 15,000 X .75 = 11,250 ) if i dont let the motor spin at a min. of 10,000 it gets real hot and the cylinder head will turn black ( HOT )

I dont know if this is right or wrong, its what i do, and i NEVER have ANY engine problems what so ever.

Wahlrite

STG

My Feedback: (26)

My gues is that you have a 13 x6 and not a 13 x8 turning 12,500

From http://www2.towerhobbies.com/cgi-bin...?&I=LXBY47&P=0

Engine guru Clarence Lee tached this engine w/various props
Prop Size RPM
13x6 12,500
13x8 10,400 using a 13x8 prop,
13x10 9,500 Hobby Services tached this
14x6 10,900 engine at 11,300 rpm
14x8 9,500 6-24-99
14x10 8,400
15x6 10,200
15x8 8,100
16x6 8,300

Looking at these #'s it is easy to see that the 15 x6 will give you the most thrust, while still giving plenty of forward speed( 6 pitch prop turning 10,000 rpm). My empirical tests have proved the same results.