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From: "Hapgood, Matt" <matt.hapgood@funb.com>
To: lancair.list@olsusa.com
Subject: alternate air for a turbo engine
Date: Mon, 17 Apr 2000 15:07:34 -0400
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First Union Securities, Inc.

Someone posted this morning (before my computer crashed) about a spring
loaded alternate air door.
Also said it was spring loaded and getting filtered air.
I am confused, so I will ask my questions precisely -
1.  Is this door automatic, or is the spring to keep it shut until manually
opened?
2.  If manual, is it by a "pull" type of cable?
3.  How is the air still filtered?  I thought the idea would be to get the
air after the filter in case the filter is clogged?

As background, here is the layout of the air for my 360 Lycoming:

1. Air enters through the lower snout on the Lancair cowling (standard lower
cowl for long engine mount) 
2. into a scat for about 6" then into an airbox (which is mounted to a
bracket on the bottom of the engine)
3. the air box is about 3" high and 6" wide, and extends about 14" towards
the back of the engine
4. at the top of the rear of the airbox is the airfilter - a rectangular
bracket filter
5. air is routed straight up, through the filter and then funneled
6. into a highly contorted scat tube (about 12")
7. which leads into the turbocharger intake (at the rear of the engine)
8. then out of the turbocharger (hopefully compressed and without fragments
of an impeller...)
9. into a short pipe to the intercooler
10. from the intercooler into a long series of tubes into the throttle body.

whew.

Any suggestions for alternate air?  Do I really need one (gliding isn't my
specialty)?  Right now there is none.  Ideally I would like a simple
solution - like a spring loaded door after the air filter that would work
kinda like the opposite of a wastegate - open when the vacuum (in the area
after the filter) indicates a blockage.  Not that I know what that pressure
would be ...  (It's a turbo normalized engine...?)

Matt Hapgood -
L360 that has sucked my social life and wallet dry...
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Please send your photos and drawings to marvkaye@olsusa.com.
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