X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail-qa0-f42.google.com ([209.85.216.42] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with ESMTPS id 5601462 for flyrotary@lancaironline.net; Fri, 15 Jun 2012 08:57:52 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.216.42; envelope-from=rwstracy@gmail.com Received: by qafi31 with SMTP id i31so162653qaf.8 for ; Fri, 15 Jun 2012 05:57:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:references:from:content-type:x-mailer:in-reply-to :message-id:date:to:content-transfer-encoding:mime-version; bh=+pN8spWydLIO0p+wlDyDpExcUH1uv1o6lETge0O8kdA=; b=i51eWQ1M7M0tPnDoS1vNmRYYzOwkY6MP8RZKpUAK3iPBvnxmgxImdXPCLR+e4VEWZA L5XAS47AbcT1tP5ntZ7e4K5oXUuORZAOWrZDR/ni3mC4N9wplkyvl+l/iO4uxQHJyDKs TSw3LbMfiFcOAxpp1A0oBhex3JL5vlZCfnv1xDWzdQOHiI0NNkscx3NnIszUwokihKKh MQUbm4y0ApYE4VbkNMjUNacwPH7JVtAhUh633Y1I7z+WCJcULUNz4jMGyDtHK3er+71v 8Wer8nv5mBw+ZvOYS/19l/iqFcsEzspfbJRHQpWWrpUoOO2SzOpPW0kL3M66XDOVp/UV mCiw== Received: by 10.229.105.166 with SMTP id t38mr2839081qco.136.1339765035901; Fri, 15 Jun 2012 05:57:15 -0700 (PDT) Return-Path: Received: from [192.168.1.3] (173.sub-166-248-83.myvzw.com. [166.248.83.173]) by mx.google.com with ESMTPS id dq7sm22329368qab.0.2012.06.15.05.57.14 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 15 Jun 2012 05:57:15 -0700 (PDT) Subject: Re: Cooling Details. References: From: Tracy Content-Type: text/plain; charset=us-ascii X-Mailer: iPad Mail (9B206) In-Reply-To: Message-Id: Date: Fri, 15 Jun 2012 08:57:10 -0400 To: Rotary motors in aircraft Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (1.0) Engine cooling seems to be an almost universal challenge to alternative engi= ne users. As I make small changes to my system I am more and more convinced= that it is all the details and parts of the system that makes it a success o= r failure, not just one key part like size of the heat exchanger. This con= clusion was recently reinforced while working with another RV builder who ha= s an almost identical cooling system (at least in verbal description, I have= n't actually seen it) to my own. Mine is working OK, his is overheating. Last week's cooling experiment result was a surprise to me. My RV-8 cooling= system was already adequate but on climb out on hot days the oil temps woul= d still be at redline with full power and that makes me feel like I have les= s margin than I'd like. Hoping to loose a couple of degrees I decided to sm= ooth the sides of the exit duct where the air has to go around the 3/4" flan= ge of the firewall for about 2" on both sides of the exit. I had already in= creased the radius of the stock firewall at the top of the exit. Just addi= ng a small piece of sheet aluminum to the sides of the exit was the change. = Took about 10 minutes to make and install. They form a ramp to guide the a= ir over the firewall flange so the air doesn't get tripped up going over it.= At least that was the theory. The improvement was all out of proportion t= o what I expected. Don't know the exact number of degrees but it's enough t= o make a world of difference in my comfort when I'm scanning the gauges on c= limb out. =20 This obviously is not a magic answer to all cooling problems but I think it= illustrates that any one of many details can be the weak link in your cooli= ng system. =20 Tracy=