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s.d.50-90lx

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Old 09-02-2008, 09:51 AM
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russm
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Default s.d.50-90lx

replaced my 75ax-pits muffler w/ the 90lx-turbo muffler setup in my h-9 sundowner. started w/ an apc 10x10 prop, 13,600 rpm. tried a 12x8 apc, 13700. then went w/ a 11x7.5 wood prop, 14300. i did not have a 11x8, which is what i would have used. i was thinking i should be geting around 15000 and up in that range . this should be a blistering setup. not much faster than the previous setup. the engine is runing very well overall. transition is excellent.using 15% synth fuel w/ os f type plug. there will be a radar gun at the field this weekend. i was hopeing to top dubs 135 mph mark. very nice plane. well put together. any thoughts for higher rpm numbers? also am geting some leaking around the muffler connection. thanks,russ
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Old 09-02-2008, 11:46 AM
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Default RE: s.d.50-90lx

The turbo-jett is not tuned for real high rpm....

The regular 90L jett-stream likes around 14,000.
The 90LX muffler likes 15,000.

TurboJett for that size engine typically is set up to run around 11,500 to 13,000 rpm with a bigger prop like a 13x6 or 14x6 or similar. It is effective well beyond that..... for your application somewhere around 13,000 to 14,000 rpm. Maybe 14,500 it should hang in there, but it will be a governor much beyond that.

You lose some rpm here, but you gain in torque. Use the torque.

That is why you didnt see the 10x10 climb beyond where the 12x8 spun up to.

The 11x7.5 was about right at the upper rpm limit.

It is going to be a bit of a trick matching the 90LX sleeve timing and the turbojett rpm preference. The torque will help the engine run stable on the ground and will also help it unload in the air.... so you can take advantage of that. Try and keep peak ground rpm above 13,500 with what ever prop selection. The engine should unload a bit and the porting will work better once in flight and the prop unloads.

You might want to try that 11x8, 11x9, and even an 11x10.

Set the engine down from peak rpm as normal then see how it unloads in the air.

Bob
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Old 09-02-2008, 02:10 PM
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Default RE: s.d.50-90lx

russum:

Gotta admire your aspirations!!!! Sort of reminds me of when Billy Cohen decided to slug it out with Joe Lewis. he he he
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Old 09-13-2008, 09:41 AM
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Default RE: s.d.50-90lx

turned out to be a very nice setup. got in a lot of flights last weekend. was estimnated at around 150 by some ex-racers. who knows? it feels about as fast as my pred w/ a rossi 40. aside from the speed, i get a lot of comments about the turbo muffler,and not good. hope to get this setup radared sometime.
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Old 09-14-2008, 09:37 PM
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Default RE: s.d.50-90lx

Sounds like it is running fairly well.....

As far as I know you are the first one trying to actively run the LX with the turbo on it.
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Old 09-15-2008, 09:36 AM
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Default RE: s.d.50-90lx

did not have a choice w/ this setup. the engine has never run better. transition is perfect. feels pumped. had to remove a lot of cowl for the muffler, but well worth it.i get a lot of questions about the muffler. glad i finally found the right plane for this engine. best wishes to dub and his family and co.
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Old 09-15-2008, 09:39 AM
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Default RE: s.d.50-90lx

Thanks Russ.......

send me a few photos when the opportunity permits.....

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