str86diesel

Hello everyone,

I was hoping that you guys can steer me in the right direction. I have been working on breaking in my OS 46fx with an 11x6 MA prop. After the 5th tank of fuel I started messing with the carb. Due to the fact that the engine was way to rich and it stutters when going into WOT.

After leaning out the motor just a bit, I am seeing about 9400RPMS with the 11x6 MA. Is this a Low reading or does it sound about accurate? I still need to lean the motor out a little, but I wanted to break it in with another tank or 2 first.

What do ya'll think?

Thanks

Kev

Pepe J

My Feedback: (2)

Hey Kev,

I does sound like the RPM is low? I have ran an 11x6 APC on mine, but it was some time ago. I recall the RPM to be in the mid 11's from what I remember, but then again were comparing an APC with a MA.
Something to keep in mind here, a 46 FX is a ABC/ABN type engine. It is a definite NO-NO to break-in these engines type's "slobbering" rich, only engines with ringed pistons. I've always ran my engines up to max. rpm @ WOT and turned the high speed needle out a little to richen it up just a hair. You want to run it as hot as possible, but not to the point where it is about to overheat.
First two runs @ 5 minutes with cool downs in between. Next couple of runs @ WOT, I lean it out a bit/back to rich a bit by just turning the High Speed Needle.
It sounds like the low end needle may need some adjusting and the MA prop may be putting a little to much load on it for break-in. You may want to try a smaller prop or an APC.
I will see if I have an MA 11x6 in my collection and run it up for you, but I don't think so?

Happy Fly'n....

str86diesel

Thanks for the reply. I did lean the motor out quite a bit before I first started it and make sure it wasn't slobbering rich. Though I wanted to make sure it was rich enough to still give me a good smoke trail (being that it is kind of chilly outside, mid 30's, and due to the high altitude). The only thing that was really rich was the low speed needle, in which I have leaned out. I am going to run another tank through the motor tomorrow and lean it out more to see what kind of revs I can get out of it again.

Thanks for the good info I really appreciate it.

Kev

Pepe J

My Feedback: (2)

Hey Kev,

Good to hear, sounds like you've done things correctly for Break-in. I did not take into account that you live in the "Mile High" City, so that will take away a few RP's for sure. It does still seem to me that MA 11x6 maybe just a bit to much prop? I've never used one so I can't really pass judgment.
What % of Nitro. fuel and glow plug are you using? Considering the Altitude, the engine is new and if you are using a low Nitro fuel, the RPM may not be far off. I think you will be fine running the engine and it just needs some more time on it.
I plan to go out fly'n tomorrow, weather permitting. I don't have a MA 11x6, but I'll see if I can locate one (I'll keep you posted if I do). I use a Bolly 11.5x5 on mine for all around sport flying which is my prop of choice and a APC 12x4 on the "Profile" I fly. I'm going to give a 12.25x3.75 a try when I come across one.

Happy Fly'n....

str86diesel

Thanks for all of your help, I really appreciate it. As far as fuel, I am using Cool power 15% nitro.

I am also going to play with some different props to see what kind of revs I can get. I have a few APC's, Top Flite, and zinger props laying around. Hopefully I get better performance from them..LOL

Again, Thanks for your time and assistance.

Kevin

str86diesel

Well, I found out today that the problem is with my Carb. The low speed needle has a small crimp in it. I did my best to fix it. I'm going to buy a replacement carb and put this one in the tool box...

I would still be interested to see what your tach is reading with an 11x6 though.

Kev

Fredde Flygare

Kev,

Your RPMs seem to be on the low side. With 5% nitro and 16% Aerosynth 2, I get the following readings with my 46FX using the standard silencer:

APC 10x7: 12800
MA 11x6: 12500
MA 11x7: 11600
RAM 11x6: 11800
APC 11x7: 10700
APC 11x8: 9700

Cheers,

Fredrik

Pepe J

My Feedback: (2)

Hey Kev,

I threw an MA 11x6 on mine today. With out any tweak'n and pinning the throttle I got 12,300 15% Nitro / 20% Oil (75%syn-25%cas.)

str86diesel

Thanks guys. I can see that My carb was have been worse then what I thought...LOL

I am going to buy a new carb this week and then get back to the drawing board.

Kev

dpsper

Kev,

Do you still have the baffle cone inside the muffler?
I removed mine since day one and have always been using either an 11x6 or 11x5 MA or APC. I have used 9 gallons of fuel it in the past 3 years and consistently turn 13,300-13,800 on 15% Morgan fuel. Get your carb tuned for a snappy transition to WOT and let her rip. I can peak at 14,300 but that is way too lean.

str86diesel

I do still have the baffle in the muffler, not knowing if it really is needed or not, I chose not to remove it.

So I can remove it and still have the motor runnind safely? Back pressure is not an issue?

Thanks

Kev

IXLR8

My Feedback: (55)

Taking the baffle out will increase your RPM and I found that mine run as well if not better with them out. I also generally use a 10x8 on my os 46s which they seem to like better than an 11" prop. Switch over to APC and you will notice a big difference.

str86diesel

Ok guys here's the latest.

I totally rebuild the carb, got her running pretty good now. I took off the MA 11x6 nylon prop and put on an MA 11x6 wood prop.

After 1/2 a gallon of fuel total through this motor, I am now peaking at 11,100, so I turned it down to about 10,800rpms.

Is this at least decent now? I figured after a couple of more tanks, I can probably get her up to about 12k.

Thanks for all of the advice you guys have given me..it is much appreciated.

Kev

Gizmo-RCU

My Feedback: (27)

Try an apc 10x7, should give you lots of revs. and work well on most applications. My ST 51 turns 13,000 plus on the bench with that prop and hauls---- give it a try.

Pepe J

My Feedback: (2)

Hey Kev,

Something maybe Cah-Cah with that engine? If it is still under warranty, ship it back if things don't improve.
My engine and Fredde's are pulling approx. the same RPM's and this should give you a Ball Park figure what an MA 11x6 should be twisting at. Removing baffles and running 10" props. is not going to cure your problem. It would be nice to know what RPM's others are getting at the 5K level?


Happy Fly'n....

ShempHoward

My Feedback: (3)

Don't forget he's in Denver which is a mile high in altitude.

At sea level here in San Francisco on Cool 15% (klotz enhanced to 20% syn-oil) Fox Long Idle Bar Plug.

MA 11X6 12800 flyably rich
MA 10X6 13800 " "

JimTrainor

Round about 1000 ft ASL

15% Omega, Tower Muffler, 12x4 APC, 13500
15% Omega, Jett Stream exhaust 11x5 APC 14500 (very loud)
15% Omega, Jett Stream exhaust 11x6 APC 13500
10% Omega, Macs Quiet pipe, Perry V30 pump, 11x7 APC, 12500

All A8 plugs.

I may be able to do better than 12500 with the 11x7. It's the first time I've tuned a pipe. Also, I may or may not get a small boost when I test with 15% fuel. I've read 15% is can be too high when used with a pipe.

The 11x7 at 12K+ with the Macs quiet pipe was more than 10 dB quieter (at ~20 feet) than the 11x5 at 14k+.

DarZeelon

My FX turned the MA 11x6 at 12,400, on 5% nitro 20% synthetic-Castor oil mix fuel. The muffler was the stock 873, with the baffle removed.

Changed to a Bolly 11.5x6 prop and RPM went down to 11,600, but vertical performance was transformed. My WM T-34 pulls straight up until out of sight. It also unloads more significantly as flight speed increases.

I replaced the muffler with a Tower.46 unit and got RPM back to 12,150 with the Bolly prop. The model now accelerates straight up, from zero speed hover.

This tells me the MA is not very efficient and is under-pitched.

Sincerely,

Pepe J

My Feedback: (2)

Gotta like them Bolly's.....


Happpy Fly'n....