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Date: Sun, 14 Jun 2009 19:22:04 -0700
From: Don Wallker <drwalker@gbis.com>
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To: flyrotary@lancaironline.net
Subject: A big win!
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RV-8 Renesis N113BR
EC-2 EM-2 RD-C
Catto 76/88 Tuned intake 17.5 inches, Tuned exhaust 24 in
Flys like an RV, quietest plane on the field. 3.5 hours in the air.  My 
legs have stopped shaking when I fly.

 Thanks to the 2 guys who added cowl flaps and solved their cooling 
problems.  I listened to them and others who had conflicting views here 
at Stead.  The conventional wisdom is that the discharge air from the 
cowl needs to be about 80% of the incoming air.  At least for air cooled 
engines.  One guy mentioned that the Sube flyers had a way to cool 
better by cutting holes in the outside bottom of the cowling just 
forward of the firewall and putting scoops on the inside to direct the 
air out.  Since the pressure is higher on the outside of the cowling, 
there has to be a reverse scoop (facing backwards) so there is a low 
pressure area and the air will flow out.  On the stock RV cowl, the 
factory inlet area is about 50 sq inches and the outlet about 50 sq 
inches too. My inlet is about 44 sq in as I use part of the left cheek 
for the  intake manifold.  The sube guys figured out that the outlet has 
to be 1.5 to 1.8 times bigger than the inlet.  I cut my cowl (ouch) and 
added about 17 sq inches per side on the bottom for a total of 34 sq 
inches additional discharge.   Where I used to climb out at 205 oil and 
195 water on a 40 degree day.  I'm now climbing out at 175 oil and 185 
water on a 60 degree day.  Running a little cool during cruise so will 
be building adjustable cowl flaps with servos.  I'm not yet developing 
full power, so sizes may change.  I'm using an oil cooler slightly 
larger than stock and the radiator that Tracy is using in his RV-8 so I 
am probably over radiatored.  Of course I can't at present find the Sube 
file where I got this info, but I find it later and send it.  Cooling is 
still not very good on the ground and on hot days the taxi will have to 
be short.  Once in the air it is great!
Thanks for the write ups by Ed and Al.  I not only learned, but took 
action.  Added battery back up for my Dynon EFIS in case I my electrics 
fail, I will still have airspeed and altitude.  I added a canopy switch 
that turns OFF a big panel light when the canopy is latched TIGHT and 
added it to my checklist.

Don Walker