Return-Path: Received: from [65.33.165.125] (account marv@lancaironline.net) by logan.com (CommuniGate Pro WebUser 4.2.5) with HTTP id 477173 for lml@lancaironline.net; Mon, 18 Oct 2004 12:02:49 -0400 From: "Marvin Kaye" Subject: Re: [LML] Plenum cooling To: lml X-Mailer: CommuniGate Pro WebUser Interface v.4.2.5 Date: Mon, 18 Oct 2004 12:02:49 -0400 Message-ID: In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset="windows-1252"; format="flowed" Content-Transfer-Encoding: 8bit Posted for "George Braly" : Mark, The larger plenum volume is doing something useful. Did you come to Ada? If so you saw the wild and chaotic air flow conditions under the cowl on the video with the tuft testing done inside the cowling. From what you wrote, I think your understanding of the physics is a bit mis-placed. The air does not “expand” and cool as it enters the larger volume plenum, it actually compresses and the pressure and temperature RISE - - just the opposite of the process you describe. The temperature rise is rather negligible and is recovered as the air accelerates down through the cylinders. The problem with the low volume plenum design arrangement is that the airflow in and around and down and through the cylinders becomes much less predictable - - with the real risk of there being complete “zero flow” areas. That is exactly what we found last week on the RV-8 that was here with the high tech – low volume – (nearly impossible to work on the engine) plenum coupled to the “hi-tech” style cowl inlets. Regards, George """ The air in this chamber isn't doing anything useful. The volume as the air is passing the cylinder cooling fins may be what's important. If the air expands and cools above the engine but speeds up and heats up as it goes past the cylinders, have we gained anything? """