Return-Path: Received: from [24.25.9.102] (HELO ms-smtp-03-eri0.southeast.rr.com) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 3047894 for flyrotary@lancaironline.net; Fri, 27 Feb 2004 10:07:59 -0500 Received: from edward (clt78-020.carolina.rr.com [24.93.78.20]) by ms-smtp-03-eri0.southeast.rr.com (8.12.10/8.12.7) with SMTP id i1RF7laC006360 for ; Fri, 27 Feb 2004 10:07:52 -0500 (EST) Message-ID: <000a01c3fd43$7a386be0$2402a8c0@edward> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Compression sucks! Date: Fri, 27 Feb 2004 10:07:52 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 X-Virus-Scanned: Symantec AntiVirus Scan Engine Hi Finn, That compression sounds a bit low for a rebuilt engine even at 100 rpm. I have found that if ends of the side seals are not trimed to be very, very close (but not touching) the round corner seal, compression at low rpm may suck. This condition does not seem to hurt medium to high rpm operations but it makes it hard to start at low rpms. Try squirting some light weight oil (say 10 weight) into the spark plug hole turn it over a couple of times before hooking up the compression checker. Your low rpm compression should show considerable improvement. Another thing. Can you tell anything by observing the compression gauge needle movement. For instance if you have two faces with low compression and one with adequate compression on a rotor, it is probably an apex seal between two chambers. If the compression is the same for all faces of a rotor but low, it could indicate inadequate sealing by the side seals. I tried to be overly cautious and put too much oil in my gas on break-in and ended up losing compression. I know it sounds crazy, but my compression dropped from an initial 110 psi (before I put additional oil in the gasoline) to around 70 psi during cranking. I couldn't figure out what the problem was, then Leon described "poisoned gasoline". The theory is too much oil in the gasoline, causes the apex seal to ride on a thick film of oil around the rotor chamber. As the chamber starts to compress the air, the pressure "blows" through this oil film past the apex seal losing compression. I initially thought it was a crazy idea, but following Leon's advice, I drained all of the "poisoned gasoline" and filled the tank with new gasoline with the proper oil mixture and within a couple of minutes of running my compression was back. So I would mix my oil with the gasoline the same as for operation and not over do it. My engine continue to show slow improvements in compression up to the current 120 hours of run time. Now if I could just wade through the 14" of snow we received over the past 24 hours and get to my workshop, I could finish wiring up my DIE intake manifold. Ed Ed Anderson RV-6A N494BW Rotary Powered Matthews, NC ----- Original Message ----- From: "Finn Lassen" To: "Rotary motors in aircraft" Sent: Friday, February 27, 2004 9:31 AM Subject: [FlyRotary] Compression sucks! > Finally brought a compression tester to the airport yesterday. 30 - 45 > psi at low (maybe 100 RPM). > > So, I'm definitely going to install some kind of primer. > > How many hours is it going to take for apex seals to seat better? > > Any recommended RPM for running in the engine? 4,500, 5,000, 5,500? > > Mix extra or less oil in the gas during this? > > Hoping to have right radiator installed this weekend, so I can start > running at full power. > > Finn > > > >> Homepage: http://www.flyrotary.com/ > >> Archive: http://lancaironline.net/lists/flyrotary/List.html >