Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml
Date: Tue, 11 Mar 2003 13:51:31 -0500
Message-ID: <redirect-2049483@logan.com>
From: olsen25@attbi.com
Subject: Engine cooling in 320

Greetings,

First, a big thanks for the recent discussion on stiffening the 320 cowl.  I 
am encorporating many of the suggestions and look forward to a crack-free 
cowling for many flight hours.

One of the issues brought up in the cowling discussion is the "trumpet horn" 
or "ramps" just inside the cooling air inlets on the cowl.  I completely 
understand how and why this works and is optimal.  However, is it really 
necessary?  I also understand that a plenum is the most optimal solution 
(Brent Regan convinced me of that a few years ago).

My 320 is a couple months from flying and I am in the process of finishing the 
top of the cowl.  The cooling arrangement I have chosen for my stock IO-320-
D1B (160hp) is as follows:
  o Standard factory baffling
  o Large NACA duct on the right side of cowl for oil cooler
  o "Shark gill" exit for oil cooler air on left side of cowl
  o No "ramps" inside cooling air inlets
  o Blast tubes for mags and fuel pump, taking air from rear baffle

In listening to other 320 drivers over the years, my best guess is that I 
should have just fine cylinder temps and my oil has the potential to be too 
cool.

I have heard from some 320 pilots that have oil cooler air tapped off the rear 
baffle that their oil temps get a bit high when they do more than a couple of 
touch-and-goes.  I don't want this problem.  I've also heard from those with 
NACA ducts feeding the oil cooler (and dumping hot air into the lower portion 
of cowl) that their oil temps are just fine.

With my dedicated NACA duct feed and exhaust vent for the oil cooler, I wonder 
if I will have too much oil cooling.  Also, since I am not robbing any air 
from the cylinders to cool the oil, I expect the cylinders to be just fine.  
Which brings me back to my question: "Do I need to install ramps inside the 
cowling?"

Any comments from those of you with experience in the 320/360 would be greatly 
appreciated as I am in the position of being able to do something about it 
now.  In a couple of weeks it will all be painted.

Regards!

Dan