X-Virus-Scanned: clean according to Sophos on Logan.com X-SpamCatcher-Score: 1 [X] Return-Path: Sender: To: lml Date: Thu, 07 Dec 2006 15:25:00 -0500 Message-ID: X-Original-Return-Path: Received: from imo-m20.mx.aol.com ([64.12.137.1] verified) by logan.com (CommuniGate Pro SMTP 5.1.3) with ESMTP id 1651447 for lml@lancaironline.net; Thu, 07 Dec 2006 14:46:34 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.1; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-m20.mx.aol.com (mail_out_v38_r7.6.) id q.d18.1caf069 (29672) for ; Thu, 7 Dec 2006 14:45:42 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: X-Original-Date: Thu, 7 Dec 2006 14:45:39 EST Subject: Re: [LML] High Ignition Advance Problem X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1165520739" X-Mailer: 9.0 Security Edition for Windows sub 5330 X-Spam-Flag: NO -------------------------------1165520739 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 12/7/2006 1:06:47 P.M. Central Standard Time, bakercdb@gmail.com writes: On the 2nd leg of a long cross country trip, I noticed that CHTs were running noticeably higher than usual on climb out. After leveling off at 6,500msl, CHTs were uniformly running approximately 40+ degrees higher than normal. Upon landing, the problem was eventually traced to one of my PMag ignitions that, was going to full advance at idle (39degrees). This was a failure mode of electronic ignitions that I hadn't considered before. Given the engine seemed to be running fine otherwise, I didn't try switching off one ignition in flight, which likely would have pinpointed the problem. Clark, Low MAP and low RPM are exactly the low power combination that encourages electronic ignitions to fully advance the timing. Indeed, the P-Mag may be broken (always delivering max advance), but a significant advance at idle is not a good failure indication. I regularly see 34-35 DBTDC at low RPM (idle or close to idle) and my base timing is 20 DBTDC because of a CR greater than 8.7 (equivalent to your 39 DBTDC unless your jumpers also are set for a base timing of 20 DBTDC). Perhaps the P-Mag goes to a large advance because the MAP sensor is always indicating low pressure. What happens if you set the jumpers to use RPM only for the timing? You shouldn't get much advance for operation above 2500 RPM. I have to assume the RPM sensor is working for the P-Mag to operate at all. PS: You may have experienced the kind of condition that led me to the conclusion that I must have a display of the in flight timing for any ignition that changes the timing. Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) A man has got to know his limitations. -------------------------------1165520739 Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

In a message dated 12/7/2006 1:06:47 P.M. Central Standard Time,=20 bakercdb@gmail.com writes:

<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>

On the 2nd leg of a long cross country trip, I noticed that CHTs were= =20 running noticeably higher than usual on climb out. After leveling of= f at=20 6,500msl, CHTs were uniformly running approximately 40+ degrees higher tha= n=20 normal. Upon landing, the problem was eventually traced to one of my= =20 PMag ignitions that, was going to full advance at idle (39degrees). T= his=20 was a failure mode of electronic ignitions that I hadn't considered=20 before. Given the engine seemed to be running fine otherwise, I didn= 't=20 try switching off one ignition in flight, which likely would have pinpoint= ed=20 the problem.

Clark,

Low MAP and low RPM are exactly the low power combination that=20 encourages electronic ignitions to fully advance the timing. Indeed, t= he=20 P-Mag may be broken (always delivering max advance), but a=20 significant advance at idle is not a good failure indication. I=20 regularly see 34-35 DBTDC at low RPM (idle or close to idle) and my base tim= ing=20 is 20 DBTDC because of a CR greater than 8.7 (equivalent to your 39 DBTDC un= less=20 your jumpers also are set for a base timing of 20 DBTDC).

Perhaps the P-Mag goes to a large advance because the MA= P=20 sensor is always indicating low pressure. What happens if you set= the=20 jumpers to use RPM only for the timing? You shouldn't get much advance= for=20 operation above 2500 RPM. I have to assume the RPM sensor is working f= or=20 the P-Mag to operate at all.

PS: You may have experienced the kind of condition that led=20= me=20 to the conclusion that I must have a display of the in flight timing fo= r=20 any ignition that changes the timing.

Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL (KARR)

A m= an=20 has got to know his limitations.

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