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Date: Fri, 30 Nov 2007 17:51:20 -0500
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From: Art Jensen <flycassutts@yahoo.com>
Subject: Re: [LML] Removing ram air duct from 360 cowling
In-Reply-To: <list-2510813@logan.com>
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I just removed five inches of my ram air tube on the
IO-550 in my Legacy.  I removed it because of cooling
problems with the oil.  The hard to believe part is
that it had to create a large air dam at the inlet. 
The proof is in the observed changes in the oil and
CHT temps.  I had to put my oil door back on to keep
oil temps above 170 and my CHT's used to run in the
mid 300's but now are all below 300 degrees.  With ram
air open I would see a 1.5 inch increase in MP but
with it cut it still gets 1.3 inches.  

Now I have to get the CHT's back up.  I plan to
install smaller inlets and maybe reduce the exit air
openings as well.  Will it make a measurable
difference in speed?  Don't know!

Well, that's my 2cents worth.

Art Jensen


--- kneaded pleasures <kneadedpleasures@sbcglobal.net>
wrote:

> Unless persuaded otherwise by commentary from this
> august body, I intend to remove the ram air duct
> from my 360 cowling for these reasons:
>    
>        *Never use ram air;  *It doesn't work
> (doesn't add inches of air pressure);  * It is
> draggy (perhaps add a knot of speed by removing); 
> *Making a tight seal of cowling to ram air aluminum
> structure has always, for me, been problematic
> causing some loss of ram air pressure and adversely
> affecting cooling air;  *Saves weight and complexity
> (remove one long cable and and air valve and replace
> with simplified, gently-sweeping 90-degree elbow
> into fuel injection from air-box/filter);  *Doing
> previous step permits further streamlining of
> cowling;  *Plane is now in a repaint cycle so this
> is logical time to modify cowling;  *Aircraft will
> hereafter use only clean filtered air;  *Facilitates
> removal and installation of cowling (less time on my
> back; less dirt and fewer expletives);  *Most spam
> can planes have only a single source of filtered air
> (...I think);  *Air filter will be parallel to
> airflow entering the plenum  making it very highly
> unlikely that the air-box can
>  ever be plugged so as to suffocate the engine.  Oh,
> yes, did I say that I never (except for test) use
> the ram air feature in flight?
>    
>   My loins are girded.  What thinkest you of this
> plan?   Greg Nelson
> 


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