Return-Path: Received: from pop3.olsusa.com ([63.150.212.2] verified) by logan.com (CommuniGate Pro SMTP 3.5.6) with ESMTP id 1126744 for rob@logan.com; Tue, 05 Mar 2002 11:36:32 -0500 Received: from mail.arc.nasa.gov ([143.232.48.201]) by pop3.olsusa.com (Post.Office MTA v3.5.3 release 223 ID# 0-71866U8000L800S0V35) with ESMTP id com for ; Tue, 5 Mar 2002 10:45:26 -0500 Received: from [143.232.221.83] (reinath.arc.nasa.gov [143.232.221.83]) by mail.arc.nasa.gov (8.9.3/8.9.3) with ESMTP id HAA25395 for ; Tue, 5 Mar 2002 07:48:15 -0800 (PST) Mime-Version: 1.0 Message-Id: Date: Tue, 5 Mar 2002 07:48:13 -0800 To: lancair.list@olsusa.com From: "Mike S. Reinath" Subject: Fuel Pressure Fluctuation Content-Type: text/plain; charset="us-ascii" ; format="flowed" X-Mailing-List: lancair.list@olsusa.com Reply-To: lancair.list@olsusa.com <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> I have the Vision Micro Systems EPI800 system in my 360, which recently had its first flight. The fuel pressure fluctuates between about 19 psi to about 26 psi in cruise with the boost pump off. With the boost pump on, I still see the fluctuation, but the pressure is about 2 psi higher. I have an IO360-B1B, and I am measuring the fuel pressure at the engine pump output (Tee at the pump output with the transducer mounted on the firewall). I also have a cooling shroud around the engine pump. I have a temperature sensor to monitor the temp. inside the shroud, so I know that it is working (22 deg. C at 8500 ft, 22.0 in. and 2300 RPM, with an OAT of 49 deg. F). Is this fluctuation reasonable and expected? If the engine pump is a diaphragm pump, it seems reasonable to me to expect fluctuations in pressure at the pump output, depending on when the pressure signal from the transducer is sampled relative to the position of the pump diaphragm. If the pressure is sampled just as the pulse is exiting the pump, a higher indicated pressure will probably result. If the pressure is sampled directly out of phase with the pump pulses, a lower indicated pressure will probably result. Anyone disagree? Anyone else see similar fluctuations? Test flying is going well. I now have about 19.5 hours on the Hobbs. Mike Reinath N3602M >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://members.olsusa.com/mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please remember that purchases from the Builders' Bookstore assist with the management of the LML. Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>