Finding a short enough tuned pipe...  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Finding a short enough tuned pipe...
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Finding a short enough tuned pipe... - 8/27/2005 9:02:34 PM   
Rudeboy



Posts: 3256
Joined: 12/9/2002
From: Bejing, BELGIUM
Status: offline 		Hi Bob,

I had my BSE FIRE 50 on the test stand today, doing some pipe and prop experimenting before it goes in the Diamond Dust.
I am currently using the Weston pipe that came with the West 50 and my (now destroyed) Magnum.

Now here's the problem: I have a 1" rise header on the engine, and with the Weston pipe I cannot set the pipe length short enough to use an APC 8.8x8.5 cut down to about 8" diameter.
When throttling up, it gets on the pipe at about 19000 and it tops out at about 20500 (full lean, I back it off to 19700-19800)... the engine obviously wants to give more, but can't deliver because the pipe is too long... that's frustrating

When I insert a piece of piano wire into the Weston pipe to find the end of the pipe, it shows that the pipe is about 12 inches long from the start of the diverging cone to the end of the stinger.

Do you happen to know where I can find a shorter pipe, so I can properly tune my setup?
MACS unmuffled pipes "look" shorter, but I don't know if their muffled pipes use the same "tuned part" as their unmuffled counterparts.
Do you think it is advisable to try a MACS "marine" pipe, or are these not suited for airplane use? They look pretty radical, and probably have a very narrow power band (perhaps too narrow)...

_____________________________

Revver Brother #33
...I think it needs more power...
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RE: Finding a short enough tuned pipe... - 8/29/2005 6:24:01 PM   
bob27s



Posts: 4740
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hey there...

thanks for writing.

First, yes, you can use the standard MACS nitro pipe or marine pipe. The marine pipe has a bit more volume in it too. But as you surmised, it makes the engine a bit peaky, but really gives some boost. Not too hard to deal with though with some experience. The Weston pipe should work well.

On any of the pipes, you can remove the first 1/2" of the pipe inlet itself if needed.

Just a suggestion as for the length and tuning - if you have hit that 19K+ rpm range, perhaps go up in prop size. That is a ton of rpm. I seem to recall Dub set you up with a high-timed sleeve. So getting to 19.5K to 20.5K is about right. The 8.8x9.25 when cut down might be what you want.

Perhaps leave the pipe alone where it is, and just increase the prop load. Leave the diameter up to 8.5, or go up in pitch.

When you find a prop setup where the engine does not needle well and acts goofy, that is 'past' the peak tuning rpm. At least you will know that much, and give you an idea of where things are lengthwise. Go back one prop size, and you will be right on the money.

Let me know how you make out.

Bob



< Message edited by bob27s -- 8/29/2005 6:25:20 PM >


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Rudeboy)
       Post #: 2

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Finding a short enough tuned pipe...
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