flyrotary@lancaironline.net Mailing List Archive

Chris, I don't think we have a cut and dried answer.

Certainly different airframes (pusher vs puller) certainly present different factors for consideration - I for one don't have to worry about any part of my exhaust going through my prop. Second is the heat factor, there is no question a muffler tucked up inside the cowl presents a more aesthetic (and less drag) solution - however, it also provides a high BTU oven under the cowl with attendant heat problems. I have two straight tubes 2" dia with two 3 1/2" dia shells as mufflers. I say shells because I have not been able to find any arrangement of internal baffles that survive the pounding of the exhaust pulse.

The Hush Master probably presents the best current solution if hanging it under the airframe as its fairly streamlined, can take the punishment and fairly effective in reducing the noise. The spin tech worked well, but was not streamlined and was fairly heavy. Biggest draw back was the flat surface to the airstream. I have not heard any results of the spiral type - I'm interested because I could possible stuff some in my shells.

That's my 0.02 worth

Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
http://members.cox.net/rogersda/rotary/configs.htm#N494BW

----- Original Message -----

From: the mallorys

To: Rotary motors in aircraft

Sent: Friday, August 25, 2006 4:41 PM

Subject: [FlyRotary] Exhaust system

I've looked back through the archives, and seen lots of different ideas for exhaust systems. But no real definitive answers.

There is the Cool tube exhaust that has very short pipes,like Bob White posted.

There is the medium length, no muffler system like Buly has or like Joe Hull has mocked up.

There is the really long tubes with muffler hanging under belly like Tracy has.

Do we know what the correct length tube is to tune the exhaust for our RPMs? Does this length include the muffler?

It appears the diameter most used is from 1.5 to 2".

What about the different mufflers? I only found two mufflers named in the archive that guys are happy with, the Flowmaster Hushpower II, and the Moroso Spiral Flow Racing Mufflers. Last year at Shady Bend, Monti talked about noise levels and testing different mufflers and pipes. Are there ant results from that?

I'm ready to start mocking up my exhaust, so am seeking the collective wisdom of the group.

Chris