X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-m25.mx.aol.com ([64.12.137.6] verified) by logan.com (CommuniGate Pro SMTP 5.0c2) with ESMTP id 712452 for flyrotary@lancaironline.net; Tue, 06 Sep 2005 03:32:34 -0400 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.6; envelope-from=WRJJRS@aol.com Received: from WRJJRS@aol.com by imo-m25.mx.aol.com (mail_out_v38_r4.1.) id q.8.6f70cfaa (18707) for ; Tue, 6 Sep 2005 03:31:40 -0400 (EDT) From: WRJJRS@aol.com Message-ID: <8.6f70cfaa.304e9fdb@aol.com> Date: Tue, 6 Sep 2005 03:31:39 EDT Subject: Re: [FlyRotary] Re: Another great flying day Pressurized ign harness To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1125991899" X-Mailer: 9.0 SE for Windows sub 5017 X-Spam-Flag: NO -------------------------------1125991899 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit The reason that many ignition systems fail in high altitude is a problem that I see often in vacuum systems. There is a point at low pressure (About 100-300 Torr, 760 Torr = 1 bar), that is LOW pressure but NOT vacuum where ionization of the remaining air takes place VERY EASILY. This causes electrical arcs to happen at much lower voltage. hat was described as ignition failure really was arcing to grounds outside the cylinder. Not fun. CD ignition doesn't cure this, in fact it makes it worse. If your insulator is breaking down or in the case of a big supercharged radial the cylinder pressure is up, it becomes much easier to arc through the spark plug wires than through the plug gap! This seems to be unique to this fairly low pressure (in air) situation, which can be duplicated by a vacuum chamber in which you are pumping down while you are running a supply current to something in the low pressure. (don't ask me how much it cost to re-discover this problem) Bill Jepson -------------------------------1125991899 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

The reason that many ignition systems fail in high altitude is a pr= oblem=20 that I see often in vacuum systems. There is a point at low pressure (About=20 100-300 Torr, 760 Torr =3D 1 bar), that is LOW pressure but NOT vacuum=20= where=20 ionization of the remaining air takes place VERY EASILY. This causes electri= cal=20 arcs to happen at much lower voltage. hat was described as ignition failure=20 really was arcing to grounds outside the cylinder. Not fun. CD ignition does= n't=20 cure this, in fact it makes it worse. If your insulator is breaking down or=20= in=20 the case of a big supercharged radial the cylinder pressure is up, it become= s=20 much easier to arc through the spark plug wires than through the plug gap! T= his=20 seems to be unique to this fairly low pressure (in air) situation, which can= be=20 duplicated by a vacuum chamber in which you are pumping down while you are=20 running a supply current to something in the low pressure. (don't ask me how= =20 much it cost to re-discover this problem)

Bill Jepson

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