os 91sx-h for pattern
 

just grabbed one of these engines in hopes of sticking it in a ca widebody 60. have many questions on how to set this engine up for aircraft use. does it run well inverted? and so on. what kind of fuel is used? what are the prop recomendations for break in? I'd appriciate any advice. thanks

os 91sx-h for pattern
 

You should be able to use it just like any other reliable sport motor. It likes 15%-30% Nitro and for Pattern perhaps a 15X10 prop.The question arises what type of an exhaust system will you use as this engine is more powerful than the 91FX but still might benefit from a stock 91FX exhaust system other wise your looking at a pitts style or tuned pipe.

os 91sx-h for pattern
 

going to see what I have to work with for room in the belly pan for a tuned pipe... started building the belly tonight so I should have a better idea sometime in the next few days. do you know how these engines run inverted?

os 91sx-h for pattern
 

esport33,

I am also using the 91SX-H on my WB60 as you know.
I haven't run mine yet, but here are the things that I found.

Break-In
Break-in prop suggested by OS is APC 15x8.
I am planning to use 14x8 to break-in.
I will probably use 16x4W after the break-in.

Spinner & adapter nut
With a TT 2.5" backplate and APC 16x8 on the shaft, there is no shaft left for the prop nut. Not sure how thick is the 16x4W hub is.

If you are going to use Tru Turn spinner,
you may need a reach through prop adapter. I haven't got the E-mail reply from Tru Turn yet, but I will call today to findout which one and post the part number here.

If you aren't going to use Tru Turn spinner and use plastic spinner, make sure that the backplate of the spinner is thin enough.

Throttle linkage on carb
Throttle linkage of the 91SX is similar to full length servo arm, and the shaft for throttle arm is also very long.

In WB60, I think it is fine with original if you cut half of the arm because there is a large cowl space wide enough for the engine.

If you are going to install the engine in a narrow engine mounting area, you will need a new throttle arm, and may have to cut the shaft also. I am going to use the throttle arm from Thunder Tiger 46 that has a set screw on it. It has 1mm larger hole. I may cut the shaft that the throttle arm goes on.

What heli guys talked about this engine
I found many of those Heli guys talking about this engine.
Vibration, mid range problem.

The solutions to this were
Installing an extra shim to the engine to lower the compression.
Perry pump for midrange. I will use pump after break-in.
You can still use upto 30% nitro, but lower nitro (below 20%) works very well.

I am not sure if the engine will cause vibration at high rpm when installed in a plane. I will have to run it to find out.
Heli guys who used the solutions were happy with this engine.

Exhaust
Since the engine does not come with muffler, you will need to find one that you like.

Ultra thrust muffler from Performance Specialties, and Jett muffler are available for about $70 ~ 80

I believe you can also use the muffler from OS 91FX, and probably from the Magnum 91AR also.

Another way is to use one of the Heli muffler that similar to the tuned pipe that we use on planes, but considerably short and has a little bit larger diameter.

I am going to use a Macs (muffled or quiet) Tuned pipe with modification to the fuse to accept the long pipe.

I will post more when I find out.
Hope this helps,

os 91sx-h for pattern
 

thanks Pattern. I have the fuse built and am getting ready to get into the bellypan tomarrow, I'm wanting to use a tuned pipe in mine as well let me know the part #'s from Mac's when you get to that point. are you going to instal the engine inverted? it seems the cleanest way of going as far as the cowl is concerned. let me know what you find out. eric

os 91sx-h for pattern
 

Eric,
I just got an E-mail from Tru-Turn on the prop adapter for 91SX-H
The part number is TT-019A.
This is one for the OS 77VR-DF.
It comes with a prop washer also.

Hope this helps,

os 91sx-h for pattern
 

thanks patternflyer, I need to get that ordered tonight. just about done with the fuse. MK bellcrank installed real well. have you explored what tuned pipe to use yet?b

os 91sx-h for pattern
 

Eric,

the adapter partnumber is TT-0519A.
I missed one digit in the previous post.

Central Hobbies has them. I just ordered one and a few props to use. Just got a Macs Quiet tuned pipe.
I will be running probably next week after receiving another pipe.

os 91sx-h for pattern
 

I found the adapter at horizon hobbies for 9 bucks and place the order. Central sold me the tt ultimate 120 cut spinner for 25. that was a deal. check with them if you're still needing a spinner. I'll be looking for you're recomendation on a tuned pipe since I still need to grab one. thanks

os 91sx-h for pattern
 

Well, I called the Central Hobbies after reading your post, but they told me they don't have the Ultimate 120 cut for that price.

Which size are you talking about?
I asked them for Ultimate 2.25" 120 cut. They told me it is a light backplated one for $32.00

os 91sx-h for pattern
 

Eric,

I just ordered a Macs standard header for 91FX. It is same mounting with 61FX, but has larger diameter pipe for 90 size tuned pipe.

If you are done with the fuse, can you find out the header clearance? How far should it be from the fase of the exhaust port to the center of the exhaust header pipe?

I am not sure which one can fit in the fuse ( standard header 1-5/8", Long 2-3/8", ExtraLong 3-1/8").

I am still waiting for another tuned pipe to arrive. Hope it is lighter. Macs Quiet pipe weighs 180grams with mounting. Standard Header for a 90 weighs 83 grams with coupler.

That is almost 9.25oz.

I am also waiting for a reply regarding a carbon tuned pipe from Taiwan. It is very light and can be use on 140 also. I will post again when I finalize the deal.

Let me know

header
 

I haven't yet built the bellypan portion of the fuse so I'm still flexable with the header and pipe. just not too sure how easy it's going to be removing the one piece wing with the tuned pipt down there? anyway, I still would like to pull it off somehow. Are we assuming that the engine is mounted inverted? I can still pull a measurement for ya once I mark off the height of the horizontal on the bulkhead. I'm leaning on a mac's header and a shorter pipe mounted to the outside...but ,, I just haven't been there yet. eric PS. get two if you strike the deal with taiwan, I'm going to be building the Fantacy next and will need a good pipe for that one.

os 91sx-h for pattern
 

We have side mount the engine.
It is possible to mount the engine inverted, but it will require custom wrap around header to have the exhaust out through the center of fuse bottom.

os 91sx-h for pattern
 

yes, sorry.... I knew that. I've been up late finishing the wing all night! I'll get the measurement asap.