Return-Path: Sender: "Marvin Kaye" To: lml@lancaironline.net Date: Wed, 16 Mar 2005 19:35:30 -0500 Message-ID: X-Original-Return-Path: Received: from mta9.adelphia.net ([68.168.78.199] verified) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 795831 for lml@lancaironline.net; Wed, 16 Mar 2005 08:50:01 -0500 Received-SPF: pass receiver=logan.com; client-ip=68.168.78.199; envelope-from=glcasey@adelphia.net Received: from worldwinds ([70.32.213.236]) by mta9.adelphia.net (InterMail vM.6.01.04.01 201-2131-118-101-20041129) with SMTP id <20050316134913.ZEKD12278.mta9.adelphia.net@worldwinds> for ; Wed, 16 Mar 2005 08:49:13 -0500 From: "Gary Casey" X-Original-To: "lancair list" Subject: Re: supershargers X-Original-Date: Wed, 16 Mar 2005 05:41:55 -0800 X-Original-Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.2416 (9.0.2910.0) Importance: Normal X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 <> It might be count-intuitive, but the power required to run a supercharger goes up if the flow rate goes up such as from dumping air downstream of the supercharger. Throttling the air upstream of the supercharger will reduce power requirement effectively, but I'm not sure if the shaft seal in the supercharger will work with a partial vacuum in the unit. Some people have played with pre-swirl as a way of reducing the pressure ratio and that can be effective, but not over a wide range. The basic problem is that at a given rpm a dynamic compressor creates a more-or-less constant pressure ratio. An aircraft wants to run a variable compressor speed as the pressure ratio changes a lot from sea level to altitude (you probably want to run a constant crank rpm and an constant manifold pressure). A turbo handles this task relatively well, but it's not perfect either. Gary Casey