X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from smtpauth07.mail.atl.earthlink.net ([209.86.89.67] verified) by logan.com (CommuniGate Pro SMTP 4.3.4) with ESMTP id 1002642 for flyrotary@lancaironline.net; Wed, 15 Jun 2005 03:56:47 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.86.89.67; envelope-from=Dastaten@earthlink.net Received: from [24.238.206.157] (helo=earthlink.net) by smtpauth07.mail.atl.earthlink.net with asmtp (Exim 4.34) id 1DiSkf-0003As-8O for flyrotary@lancaironline.net; Wed, 15 Jun 2005 03:55:57 -0400 Message-ID: <42AFDF33.302@earthlink.net> Date: Wed, 15 Jun 2005 02:56:35 -0500 From: David Staten User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Failure to compute References: In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-ELNK-Trace: 9a30bff84e6cb88f95c85d38d22416599ef193a6bfc3dd48da70c2f268e12d8f36d45ceea9083882c839d1b4ccd7d4ce350badd9bab72f9c350badd9bab72f9c X-Originating-IP: 24.238.206.157 Ian Dewhirst wrote: >Tracy wrote "It could be argued that the exhaust energy was free anyway so >it doesn’t matter. I don't have enough real world data to back it up but >I don't think this is true." > >Back pressure rises with turbine load so you are quite right Tracy, the >energy is not free. > > I think what the point was about "free" energy is that you are using the exhaust gas, which is actually dumping up to 50% of the energy generated by fuel burn "overboard". It takes about 20-30 HP (rough round numbers from a PL graph) to compress the air needed for boost. The turbo uses the "waste" exhaust gas to do this. The supercharger uses direct mechanical energy to do so. Obviously nothing is free, but from a net standpoint, the turbo is more energy efficient than is a mechanical drive supercharger. Dave