SNestle

My Feedback: (3)

I've test run my OS91 for the first time this evening. It is in a Byron F16. 16oz saddle tanks plumbed in series. 5% byron fuel OS#8 plug.
It is slobbering rich at only 2.25 turns out on the high speed needle. I have not changed the factory setting on the low speed needle.
Floods really easy unless I pinch the line with hemo's until right before I hit it with the starter. I'm assuming that is because it is inverted.
Should I be starting this with the plane upside down?
Does anyone out there know what their high speed needle setting is?

rcs1313

It sure makes it easier to start by turning it upside down. The original Byron manifold system was an attempt to reduce the flooding tendency.

Just turn it upside down and forget the problem...but now you have to have a stand to put it on...always something....

Using an inflight needle valve sure helps to get the engine running right in the air as well as using a header tank--not really necessary, but does seem to help things overall...

Rod

JimBrown

My Feedback: (2)

As rcs1313 said, it will be easier to start upside down.

2.25 turns out is a good place to start. As you found out though, it is slobberingly rich. Once you have it started, go to full throttle and then slowly turn the needle in. As you do so, you should find that the rpm's increase. Keep going until the rpm's do not increase anymore. If they start to decrease, turn the needle out a few clicks quickly, as you are getting too lean. Once you have found the spot where the rpm's do not increase anymore, again turn the needle out a few clicks so that you are running a bit rich and run the tank almost dry. Shut it down and let it cool off for 15 minutes. Refuel and do it again, but a click or two leaner. You should always see a good bit of smoke coming out the tail end. After the second tank full, you should be ready to fly.

Please make sure that you use a fuel that is designed for ducted fan engines. DF engines require more oil, about 21-23%. My personal preference is Wildcat Jet-A 5%.

Once you have the engine broken in and the high needle set, then you can start messing with the low needle, if needed. I generally find that the OS .91 low end is usually set slightly rich at the factory. You should be able to let it idle for 60 seconds, then go to full throttle without any hesitation or sputtering. If you go to full throttle and the engine sputters and belches lots of smoke, your low needle is too rich. Lean it an eighth of a turn at a time until it transitions smoothly. If the low needle is too lean, the engine will, when idling, slowly lose rpm's until it quits.

Hope this helps, and good luck!
...jim

Jackjet

My Feedback: (1)

Senstle,
Rcs13 and Jim B are right-also if you want to be able to start your Byron jet right side up-you can install a black Robart fueler in the carb. feed line-fill your jet and leave the fueler open untill you start it-no flooding-no dripping fuel-.Heres how I do it-I assume your engine is broken in right ?-(first start of the day)-remove the glow plug-fill the jet-insert the starter probe-close the fueler-open throttle fully-spin starter untill fuel sprays out-open fueler-spin starter again untill no more fuel sprays out-re-install glow plug-activate glow driver-throttle back to med. idle setting-close fueler-hit starter-engine is now running-after 5-10 secs.-remove glow plug clip-if you have a on board mix.control-set it rich and throttle up to full power-now start leaning it out-(you can tell when it is right by the sound and the smoke trail)-throttle down to idle power and listen to the sound-it will most likely be slightly rich-turn the low speed needle in about 1/8th of a turn at a time untill it will idle for at LEAST 3 mins without loading up-thats all there is to it. It is real easy when you do it a few times..........believe it or not my engine will idle inverted for 30 mins.or more and I can punch it to full power and it wont even hesitate-it just goes to full power like a turbine. I use McCoy # 9 Ducted fan plugs. Hope this helps. One more thing-I add extra castor oil to my fuel-protects that $190 piston and sleeve in case of a lean run..........



Jackjet

F900

My Feedback: (2)

Jackjet,

I just got my first OS 91 with the jet i bought, happens that the OS 91/BVM pipe are inverted. I intend to use the Wildcat (5%) and Mcoy 9 plugs, as i have had great success with using this combo with the BVM.91/96 engines using (10%WC).

Is it true to say that the OS.91 will run as good even if inverted, and that the low and mid ranges of throttle are the same as the engine was upright. It will start very easy, did not find it hard even with the Os 91 inverted.


Anyone answer this question ?

When my jet with the BVM 91 starts rolling down the runway ( breaks released after full power is acheived) for takeoff, about half way down (500ft runway) its picked up quite a bit of speed.

Another guy with is jet but with an OS 91/Ramtec fan, same method as above on the few takeoffs he did, seemed to be at a slower speed when he reached the same point down the runway.

I know there can be many reasons why, but whats the difference between an OS 91Ramtec Vs BVM 91 setup. Is it that the OS has more "pull" and the BVM produces more Rpm's

Anyone care to answer ?

Thanks

Robert

Topgun2mo

My Feedback: (45)

How are you fellas measuring your RPM? Do you paint 2 stripes on the spinner and use a standard tach or is there a different method?

Thanks

Mike

Terry Holston

My Feedback: (1)

Thats one way to do it.

Another way is get a turbine, and the ECU will tell ya.

F900

My Feedback: (2)

Can anyone answer my question above ?

Thanks

Robert

SNestle

My Feedback: (3)

Thanks for all the responses gentlemen! I will have a chance this weekend to work on it.
One thing I will be changing is fuel. My LHS only carries Byron fuel. I have added oil to it. But, is there a performance increase with the Wildcat fuel?
I just happen to have one of those Robart fueler's Jackjet! I'm gonna have to print out your sequence and read it each night before I go to bed in order to memorize it though! LOL!

JohnVH

My Feedback: (38)

I use the byrons 5%x20% in mine, runs great in an inverted byron plane. I start it with the engine inverted and plane on its wheels, works fine for me. I believe I have the MC9 plug also.

SNestle

My Feedback: (3)

Well, it would be easier for me to stick with the Byron fuel. I am not really concerned at this time with squeezing every drop of power. This is my first jet, I will be pumped if I can simply enjoy the thing for a while! Then maybe I'll try Terry's idea and get a turbine.
Say, just how does one go about telling your wife you need 5K for a model airplane? Or don't you tell her at all?

JohnVH

My Feedback: (38)

I told mine the other day what I had into my one turbine model and she didnt even flinch, then I told here I needed another turbine for the new plane, she really thought that was a good idea!:stupid: haha but didnt say no

Terry Holston

My Feedback: (1)

You are correct, the BVM is slightly smaller in Dia and the BV .91 is a higher RPM engine than the OS. Also the Ramtec fan has more pitch on the blades than the Dynamax and "Loads" the engine down, giving more "Torque" or low end thrust. launching the plane quicker. Good for grass field operation.

Does that help?

SNestle

My Feedback: (3)

Are OS#8 plugs okay? I have a few of them around. If the McCoy's are that much better I can switch to them later. But, for now I would like to use what I have.