X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 15 Dec 2005 12:30:29 -0500 Message-ID: X-Original-Return-Path: Received: from mta10.adelphia.net ([68.168.78.202] verified) by logan.com (CommuniGate Pro SMTP 5.0.4) with ESMTP id 883153 for lml@lancaironline.net; Thu, 15 Dec 2005 08:30:04 -0500 Received-SPF: pass receiver=logan.com; client-ip=68.168.78.202; envelope-from=glcasey@adelphia.net Received: from [70.34.70.106] by mta10.adelphia.net (InterMail vM.6.01.05.02 201-2131-123-102-20050715) with ESMTP id <20051215132917.MVPX22124.mta10.adelphia.net@[70.34.70.106]> for ; Thu, 15 Dec 2005 08:29:17 -0500 Mime-Version: 1.0 (Apple Message framework v733) In-Reply-To: References: Content-Type: multipart/alternative; boundary=Apple-Mail-48--420152485 X-Original-Message-Id: From: Gary Casey Subject: Re: Air Filters X-Original-Date: Thu, 15 Dec 2005 05:29:13 -0800 X-Original-To: "Lancair Mailing List" X-Mailer: Apple Mail (2.733) --Apple-Mail-48--420152485 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed On Dec 15, 2005, at 3:03 AM, Lancair Mailing List wrote: > This annalysis draws me to a trivial question I can no longer > rember the answer to. Back in the days of big lizards, when cars > (fun ones anyway) were powered by engines exceeding 400 cubic > inches and fed by carburators, the typical carburator size was 750 > to 1050 cfm. (refering to street cars here) These engines turned > twice the 2700 rpm in a typical aircraft power plant. Volumetric > efficiency would reduce the actual flow rate slightly below the > calculated value but not a whole lot. So why weren't the > carburators rated about 10 times larger than they were? > > Anyone remember the reason? > > Rob The CFM rating of a carburetor is the air flow when the pressure drop reaches some standard value - if my memory serves correctly the value was 1.5 inches mercury, a fairly high pressure drop. I calculate a 455 turning 5,000 rpm (VE=1) would require 658 CFM. Doubling the rated flow of the carburetor reduces the pressure drop at a given flow by a factor of 4, so using a 1300 CFM carburetor in the same engine would result in a pressure drop of only 0.375 inches (pressure drop is proportional to the square of air flow). The off-idle operation would be expected to suffer. Gary Casey --Apple-Mail-48--420152485 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1

On Dec 15, 2005, = at 3:03 AM, Lancair Mailing List wrote:

This annalysis draws me to a trivial question I can no = longer rember the answer to. Back in the days of big lizards, when cars = (fun ones anyway) were powered by engines exceeding 400 cubic inches and = fed by carburators, the typical carburator size was 750 to 1050 cfm. = (refering to street cars here)=A0These engines turned twice=A0the 2700 = rpm in a typical aircraft power plant. Volumetric efficiency would = reduce the actual flow rate slightly below the calculated value but not = a whole lot. So why weren't the carburators rated about 10 times larger = than they were?
=A0
Anyone remember the = reason?
=A0
Gary = Casey
= --Apple-Mail-48--420152485--