Message-ID: <001101c10248$7922a8e0$a0ca0041@mshome.net>
From: "Robert Smiley" <robsmiley@home.com>
To: <lancair.list@olsusa.com>
References: <200107011133_MC3-D7C0-9ABE@compuserve.com>
Subject: Re: Oil and lower cowl cooling?
Date: Sun, 1 Jul 2001 10:11:23 -0600
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Reply-To: lancair.list@olsusa.com

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N94RJ  360-mkII  with the short motor mounts  has been flying for two years.
The first year was in primer to shake out all the bugs, do necessary body
work, rubbing areas and any post flying fixes necessary for proper
performance and operation.  July 2000 it was painted and operates in the
Northwest area. Hot weather was not an issue in the Northwest.   I have
moved to Salt Lake City for a year and here I am bumping up with the max oil
temp problem. The IO360 runs very cool on egt and cht but the oil temps are
very high when outside temps get above 90,95 + degrees. The intakes on the
cowling were enlarged during initial construction because of the larger
engine installation.  I assumed "More horsepower, more heat, get more air."
Also I took special care to seal the baffle system to the engine and
cowling.  NO LEAKS.  the temps do not vary more than 20 degrees on any
cylinder so the top end is great. The upper end has great positive pressure.
The oil cooler is installed per plans on the firewall with the intake off
the back baffle,.  The exit is shrouded to keep that heat on an exit path
through louvers on the lower left cowl at about the 7:30 O'clock position.

I do not want to cut up my lower cowling and destroy the paint job at this
time unless and until I am sure the fix will do the job.

Questions?
What are the theories of escaping air in the lower cowl area pertaining to
velocity, low pressure, size of opening, extending lower cowling aft,
possible air vents into the lower cowling etc to scavange the hot air out?
Does beveling the aft lower cowling forward, thus increasing the open cross
sectional area improve scavanging the air or hurt it.  Conversely does
extending the lower cowling aft improve scavanging air exit.

If you had a similar problem; what was your fix?  What would you recommend
as the best solution?

I am of the opinion that there is sufficient air flow pressure to the oil
cooler for proper operation.

What are your high outside temp limitations on your 360 for climbout
performance from AGL  to 10,000msl.  Is 90+ degree temp days difficult for
most lancairs to perform within oil temp limitations. If so I can live with
that.

Thanks for your thoughtful responses.

Bob Smiley
N94RJ


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