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OS 46FX Midrange Lag
Hello,
I am running a 4 year old OS 46FX on my OMP Edge. The motor has approx. 200 flights with no crashes. I am having an issue with midrange power. When I pull into a hover I am normally at idle. I will add approx 1/3 throttle to start the hover, however when I have to add a little more to hold the hover the motor will quit for a split second. It will then catch up and produce plenty of power to pull out. During normal flight attitudes I don't notice it. I can go straight up at full problem with no problem. As you can imagine with the motor stalls at 20' the plane starts dropping rapidly until the power comes back! I have tried adjusting the low end and high end. On the bench my low end seems ok, with a smooth transition from idle to full or half throttle. My high end is running 200 rpm rich of peak. I have tried Wildcat 10% and 15% nitro and I am currently running CoolPower 20% Heli and they all do the same thing. I have also tried an OS #8 and A3 glowplug. I am running the stock muffler with the baffle out. The motor is turning an APC 12.25 X 3.75 @ 12,100 RPM's. I tried an APC 11x4 with the same results. Any suggestions as I have tired everything. Thanks |
RE: OS 46FX Midrange Lag
To lean you low speed needle may help
Be cautious and just move the needle 1/8 turn at a time and then fly. Keep the plane higher until you figure out what is wrong? |
RE: OS 46FX Midrange Lag
Thanks. I tired that today and it made it worst. Maybe I went to far. I normally check my low end 2 ways. First I let it idle for 30 seconds and then go full throttle. I look for a smooth transition. Secondly at idle I pinch the carb supply line and see how the motor quits. I want it to quit without speeding up too much (ie. too rich)
Do you have a method for checking the low end? Yea I am keeping it high until I figure out what's going on with the midrange! |
RE: OS 46FX Midrange Lag
First I let it idle for 30 seconds and then go full throttle. I look for a smooth transition
I think this is best The pinch is only a reference for early on for idle<br type="_moz"/> |
RE: OS 46FX Midrange Lag
Try some of your ground adjusting with someone holding the plane vertical
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RE: OS 46FX Midrange Lag
I guess you are running muffler pressure to your tank, but maybe try putting the baffle back in the muffler to see if that helps. Maybe you are not getting enough muffler pressure without the baffle. How far back from the engine is the tank? Seems the problem is only when the plane is vertical for awhile, could be fuel feed problem. JMHO
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RE: OS 46FX Midrange Lag
1 Attachment(s)
Do you still have the baffle, try and put it back in. That should help the mid range a bunch, but it will take away some top end rpm.
I use the "KJ" Uni-flow set up as my standard for for all my non-YS engines, works like a charm. This works like the standard Uni-flow except when the throttle is reduced the tank drops pressure almost instantly so the carb isn't suddenly too rich and helps keeps the fuel from surging into the muffler. You need a OS bubble-less clunk, (other brands are cheaper,but don't work as well). A standard clunk (cut the line so it just doesn't reach the other). Two check valves (light spring), keep these closer to the tank than the muffler. A fuel safe "T". The pink vent line goes to the forward top of the tank as usual. Fill and drain point is between the filter and tank. If the plane has sat for a few months the check valves can stick, just disconnect from the muffler and connect that line to filler pump to push than pull just a few turns, than reconnect to muffler. Tip: cut a short length of fuel line and use needle nose pliers to stretch it around the outside of your lines to help your lines from slipping off tubes and fittings. Use a sharp blade to cut fuel lines, never scissors because the pinching action of scissors can make the tube split lengthwise later on. A picture is worth a thousand words, here's a mock up: |
RE: OS 46FX Midrange Lag
QS Pilot,
The engine's behavior and response to opening the throttle in a hover, can only be determined and adjusted, with the model in hovering attitude... If you adjust the transition quality perfectly (the low-speed needle) with the model on its wheels, in level attitude, it will be too-lean, with the model in the full nose-up attitude... What you are seeing (the engine 'stumbles' momentarily) suggests too lean a setting, rather than a rich one. If it was too rich 'nose-up', it would load-up and sputter when the throttle is advanced... Even more so with the plane in level attitude. Sorry to have to contradict you, Jim. Also, to get a perfect '1/3 to full' transition; adjusting for a perfect 'idle to full', or 'idle to half', will just not do the trick... It must be done in the target attitude AND in the target throttle range. Also, regarding your fuel; 'Cruel Power' all-synthetic is not the right fuel for this engine. If you want it to run right and to last, you must use fuel that contains a reasonable amount of castor oil. |
RE: OS 46FX Midrange Lag
Dar- he did suggest that the condition is too lean. Going from level flight at idle to a 90 degree nose up attitude while giving throttle will test the tuning of an engine. You should be able to tune this out like Jim said. I use the 30 second method too, and never rely on the pinch test.
However smoothly an engine will run, I would probably have just a bit more throttle applied before pulling up into a hover. Just to be on the safe side. And, I would apply it very smoothly as I pulled up. |
RE: OS 46FX Midrange Lag
Barry,
I was referring to the words used by Jim in post #2. "To lean your low speed needle may help"... |
RE: OS 46FX Midrange Lag
Thanks everyone. I will try adjusting my mixture richer and have someone hold the aircraft nose up to test. I am also considering the bubble-less as I do notice some bubbles from time to time.
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RE: OS 46FX Midrange Lag
I have a similar engine (OS 46AX) which was somewhat gutless in the midrange area where I prefer to do my 3d flying.
I fly a 128 cms wingspan profile of a Yak 54 (scratch built) that weighs 1.95Kg, wet. My prop is an APC 12.25x3.75 The response out of hover or high alpha situations was not acceptable. The engine never quit but it was taking more than expected to react. My solution: 1. OS 8 plug 2. Very thorough inspection of fuel lines and 0 air/fuel leaks 3. Tune the HN to just shy of 12k 4. Close the idle needle to just a tad less than 1/8 turn (from original OS setting) 5. With engine running, move the throttle stick (halfway in my case) to were you think the engine shows lack of reaction and use the HN to improve the performance. Play by ear. By doing that, I optimized the sector where most of my flying takes place. I rarely go WOT with this plane but in the few WOT up lines I did, the engine never gave any indications of leaning out. I hope it helps. I know it did for me |
RE: OS 46FX Midrange Lag
ORIGINAL: freakingfast Do you still have the baffle, try and put it back in. That should help the mid range a bunch, but it will take away some top end rpm. I use the ''KJ'' Uni-flow set up as my standard for for all my non-YS engines, works like a charm. This works like the standard Uni-flow except when the throttle is reduced the tank drops pressure almost instantly so the carb isn't suddenly too rich and helps keeps the fuel from surging into the muffler. You need a OS bubble-less clunk, (other brands are cheaper,but don't work as well). A standard clunk (cut the line so it just doesn't reach the other). Two check valves (light spring), keep these closer to the tank than the muffler. A fuel safe ''T''. The pink vent line goes to the forward top of the tank as usual. Fill and drain point is between the filter and tank. If the plane has sat for a few months the check valves can stick, just disconnect from the muffler and connect that line to filler pump to push than pull just a few turns, than reconnect to muffler. Tip: cut a short length of fuel line and use needle nose pliers to stretch it around the outside of your lines to help your lines from slipping off tubes and fittings. Use a sharp blade to cut fuel lines, never scissors because the pinching action of scissors can make the tube split lengthwise later on. A picture is worth a thousand words, here's a mock up: wow thats intense.... too many frosties [8D] maybe tomorrow i will get it |
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