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Date: Sun, 01 May 2005 21:36:18 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Inserts
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rijakits wrote:

> snipped
>
>Charlie,
>
>I suggest you look also into exhaust augmentation.
>If you are already "skunk working" on something new and exhaust related, you
>might as well reap the benefits from that. It should help with cooling
>(pulls air through the radiators/oil cooler), it would provide some kind of
>fairing (streamlines the cooling exit, exhaust exit and might hide any
>muffler), it also should muffle the exhaust noise (might get away with out
>any muffler...). As the augmentation implies a mixing with cooler (...than
>exhaust) air this should muffle the noise as well. If it does not mix, it
>will at least suround the hot exhaust gases with a mantle of cooler air -
>muffling again. It should also increase efficiency as you have the exhaust
>gases do some work - should also work for a turbo (double duty!)
>Last but not least benefit: Depending on the exhaust routing ( how early in
>the duct you can introduce the exhaust pipe into the cooling duct), the
>cooler air in the duct will isolate the exhaust heat from the rest of the
>engine compartement.
>
>Just a little info from this site: http://bd-4.org/cooling_nicoson.html
>Dan Nicoson is planning a V8 installation with exhaust augmentation, so it
>is also liquid cooled and a lot of heat to be removed.......
>
>Anyway, I hope between all on this list the maximum power, lightest weight,
>most reliable system is found some time, so I can shamelessly copy the
>perfect setup!! - ...sometime when I get to build:))
>
>Cheers,
>Thomas Jakits
>

Thanks for the link; it's good reading. I've thought a lot about exhaust 
augmentation. The 2 downsides I've heard (2nd hand info only) is that 
they can actually increase drag at high speeds & that they usually 
*increase* noise levels. The 2nd is not too hard to understand & pilot 
opinions about certified planes using the technique seem universal that 
they are louder than similar designs w/o augmentation. The 1st is a 
little harder to understand. Maybe the augmenters draw too much air 
through the system.

Are you considering a BD-4? I owned one for about a year, between two 
RV-4's.

Charlie