X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml Date: Mon, 18 Sep 2006 21:03:14 -0400 Message-ID: X-Original-Return-Path: Received: from sfa.gami.com ([68.89.254.162] verified) by logan.com (CommuniGate Pro SMTP 5.1c.4) with ESMTP id 1407727 for lml@lancaironline.net; Sun, 17 Sep 2006 23:40:08 -0400 Received-SPF: none receiver=logan.com; client-ip=68.89.254.162; envelope-from=gwbraly@gami.com Received: from localhost (localhost.localdomain [127.0.0.1]) by sfa.gami.com (Postfix) with ESMTP id 0A3E429C06E for ; Sun, 17 Sep 2006 22:39:26 -0500 (CDT) Received: from sdf1.mail.taturbo.com (unknown [10.10.10.173]) by sfa.gami.com (Postfix) with ESMTP id DF08829C05E for ; Sun, 17 Sep 2006 22:39:23 -0500 (CDT) Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C6DAD4.087BF7CB" X-MimeOLE: Produced By Microsoft Exchange V6.0.6603.0 Subject: RE: [LML] Backfires LOP X-Original-Date: Sun, 17 Sep 2006 22:39:23 -0500 X-Original-Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [LML] Backfires LOP Thread-Index: AcbazihTmXRh4XK/Tt+hKNS9Z7ejcAABNyug From: "George Braly" X-Original-To: "Lancair Mailing List" X-Virus-Scanned: by amavisd-new-2.3.2 (20050629) (Debian) at gami.com This is a multi-part message in MIME format. ------_=_NextPart_001_01C6DAD4.087BF7CB Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable =20 Jim, =20 If you were climbing with CHTs in the 400 then most of the damage was probably done in that configuration. =20 =20 As to the following: =20 >>What I didn't pay much attention to was EGT while LOP which was TOO HIGH at 1550F, in my humble opinion. If anyone wants my opinion it is that the exhaust valves on the TSIO-550E can not cool themselves enough while LOP even when power is back to 28/2400 because it is still at 1550F EGT and that makes the exhaust valve so hot that the valve seat has to be wide and perfect to take all the heat ouf of the valve head, or the heat goes up the stem and burns the oil off the stem therefore wearing the stem and guide very fast.<< =20 Ah... that is the conventional theory and wisdom - - that is - - that HOT EGTs translate into HOT exhaust valves. It just turns out that isn't true. The value of the exhaust gas temperature flowing past the exhaust valve is often inversely proportional to the temperature of the exhaust valve. =20 =20 I ************* KNOW *********** that comment appears to be completely crazy and verging on the area of silly. =20 But there is good hard data on this subject going back to the 1940s' That data shows that the exhaust valve temperatures follow the CHTs - - NOT the EGTs. =20 =20 And by advancing timing, as just one example as to why this is true, one will LOWER THE EGTS - - but that will make the exhaust valves run very much hotter (along with the CHTs). =20 By retarding the timing a lot, the EGTs go VERY HOT - - but the exhaust valves get very cool - - along with the CHTs. =20 In short, EGTs do not correlate with exhaust valve temperatures very well at all. =20 =20 >> My second set of cylinders had stem and guides wore beyond limits at 82 hrs and I hadn't gone LOP for the first 40 hrs and then maybe half the time for the next 42 hrs. This is the mechanical fuse, so to speak, of the Continental engine, the exhaust valves. Now I run ROP and let the fuel save my exhaust valves and save money. I use about 4 or 5 gal. more on a 540 nm flight and go faster and quicker.<< =20 I suspect your problem was the dimensional fit of the exhaust valves/guides before you ever started your engine the first time. =20 Regards, George =20 =20 ------_=_NextPart_001_01C6DAD4.087BF7CB Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable

 

Jim,

 

If you were climbing with CHTs in = the 400 then most of the damage was probably done in that configuration.  =

 

As to the = following:

 

>>What I didn't pay much = attention to was EGT while LOP which was TOO HIGH at 1550F, in my humble = opinion. If anyone wants my opinion it is that the exhaust valves on the = TSIO-550E can not cool themselves enough while LOP even when power is back to 28/2400 = because it is still at 1550F EGT and that makes the exhaust valve so hot = that the valve seat has to be wide and perfect to take all the heat ouf of = the valve head, or the heat goes up the stem and burns the oil off the = stem therefore wearing the stem and guide very = fast.<<

 <= /p>

Ah… that is the = conventional  theory and wisdom - -  that is - - that HOT EGTs  translate into  HOT exhaust valves.   It just turns out that = isn’t true.  The value of the exhaust gas temperature flowing past the = exhaust valve is often inversely proportional to the temperature of the exhaust = valve. 

 <= /p>

I  = *************   KNOW ***********  that comment appears to be completely crazy and = verging on the area of  silly.

 <= /p>

But there is good hard data on = this subject going back to the 1940s’   That data shows = that  the exhaust valve temperatures follow the CHTs - - NOT the = EGTs.  

 <= /p>

And by advancing timing,  = as just one example as to why this is true,  one will  LOWER THE EGTS = - - but that will make the exhaust valves run very much hotter (along with the = CHTs).

 <= /p>

By retarding the timing a = lot,  the EGTs go VERY HOT - - but the exhaust valves get very cool  - - = along with the CHTs.

 <= /p>

In short,  EGTs do not = correlate with exhaust valve temperatures very well at = all.

 <= /p>

 <= /p>

>> My second set of = cylinders had stem and guides wore beyond limits at 82 hrs and I hadn't gone LOP for = the first 40 hrs and then maybe half the time for the next 42 hrs. This is = the mechanical fuse, so to speak, of the Continental engine, the exhaust = valves. Now I run ROP and let the fuel save my exhaust valves and save money. I = use about 4 or 5 gal. more on a 540 nm flight and go faster and = quicker.<<

 <= /p>

I suspect your problem was = the  dimensional  fit of the exhaust valves/guides before you ever = started your engine the first time.

 <= /p>

Regards,  = George

 

 

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