Tuned Pipe Queston  
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Tuned Pipe Queston - 1/1/2004 5:54:52 AM   
Kelley


 

Posts: 52
Joined: 4/18/2002
From: memphis, TN, USA
Status: offline 		I am building a 60 size prop jet for high speed and have never before run an engine with a tuned pipe exhaust. The plane is a highly modified Great Planes F-14. My plan is to use one of your BSE 90 rear exhaust engines mounted upright. I want the exhaust to travel straight back, past the fuel tank and then to make a 45 degree bend down through the fuselage and exit the bottom of the plane where another 45 degree bend will align it with the tuned pipe mounted under the belly of the plane.

I cannot simply invert the engine and run the pipe straight back because of interference with the nose gear. I do not want to run the pipe straight along the top of the fuselage because of interference with the canopy and poor aesthetics. I do not want to mount the engine at 90 degrees with the pipe going down the side of the plane in a more customary configuration because of aesthetics.

I estimate that the distance from the rear of the engine to the intake of the tuned pipe (underneath the belly of the plane) is about 15 inches. What will be the approximate loss of maximum RPM with this extended length? Would a muffler and not a tuned pipe be just as effective in this configuration? Am I crazy for trying to run a 15 inch connector between the engine and the pipe?

Assuming my question even has a valid answer, should I use an aluminum connector bent to fit, and insulated inside the fuselage, or should I use silicone connector tubing? Would silicone tubing at that length be hard to tie down and not vibrate wildly inside the plane? Would silicone tubing provide sufficient heat resistance with no additional insulation?


Larry Kelley
       Post #: 1

RE: Tuned Pipe Queston - 1/8/2004 2:13:50 PM   
bob27s



Posts: 4831
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Larry,

Thanks for writing. My apologies for the delay in my response. I am still trying to get my forum subsription stuff to email me with new posts. Holiday season had me all over the place too

Pipe length defines the RPM. It is a function of wavelength. Pipe length is generally measured from the exhaust outlet face to the largest (divergant) diameter in the pipe.

From what you decribed, you wish to route a long 15" long "header" that reaches the bottom of the aircraft, where it will then enter the tuned pipe.

Technially speaking, there might be a way to make this work. You would have to make the header 2x the total tuned length. But the results might be questionable due to all of the turning, back pressure and other factors. The system would not likely be much more than a big muffler. You would need some significant cooling air flowing over a long header like that too.

The exhaust temperatures involved generally require you to use a solid metal header. Flexible silicone could not be used for long runs, but is generally used at the pipe/header joint.... and that gap should be kept to a very minimum.

Now, having said all of that... depending on what point in construction you are at.....
Why not run the pipe inside of the fuselage? (RE engine, mounted up right or mounted 90 deg). It might take some creativity in relocating the fuel tank. You can extend off of the end of the pipe to exhaust out of the structure. This has been done before by others on other aircraft, but I am not aware of anyone specifically who did this on an GP F-14.

You can also run the engine inverted.... about 170deg cylinder down (not entirely inverted). This would allow a RE header to pass along side of the nose landing gear, and the pipe can be recessed (either completely or partly) into the belly of the aircraft. Similar to the pipe installations in some pattern aircraft.

A more resonable approach..., I would suggest the BSE90 side exhaust, with the stock Jett-Stream muffler. Performance with the jett-stream is incredible, and it has a broader range of RPM's to work with. You will not at all be disappointed by the performance. Looks better than the long pipe under the plane too! A full pipe requires you to match the prop/pipe/engine rpm more carefully.

Any questions, feel free to drop me an email at bob27s@hotmail.com

I hope this has been helpful

Bob Brassell

(in reply to Kelley)
       Post #: 2

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Tuned Pipe Queston
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