X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao01.cox.net ([68.230.241.38] verified) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 932220 for flyrotary@lancaironline.net; Wed, 04 May 2005 10:57:01 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.38; envelope-from=ALVentures@cox.net Received: from BigAl ([68.7.14.39]) by fed1rmmtao01.cox.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with ESMTP id <20050504145610.RLRC7629.fed1rmmtao01.cox.net@BigAl> for ; Wed, 4 May 2005 10:56:10 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Re: EGT temps Date: Wed, 4 May 2005 07:56:23 -0700 Message-ID: <000001c550b9$7063aec0$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C5507E.C404D6C0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C5507E.C404D6C0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Given the fact that EGT for a particualr engine/exhaust will vary = slightly from other identical engines as a function of "where the EGT sensor is placed ", and stating at the start that we are talking about "cruise" = power settings - not "full throttle at sea level" (in other words, we are, by definition only talking about leaning at a lower power setting, with = proper timing and proper octane, where there is ZERO possibility of detonation) isn't it true that if one adjusts mixture from rich to lean, that the = EGT will "peak" at "best fuel-air ratio" for complete combustion, and that = max power will be achieved by richening a bit from that (richen until you = get max RPM for that immediate flight condition) which will result in a = slight drop in EGT? Then, if one leans back to "peak" and then continues to = lean, one will get "better economy", and, again, EGT will decrease from what = it was at "peak". It seems you understand correctly. =20 From reading of what others have said, one can lean past "peak" maybe = 50 degrees and have a safe, economical cruise setting, maybe taking a = slight increase in throttel or manifold pressure to keep HP up to what you want = to cruise at. - The old Air Force BIG radial engines used to cruise at 80 = degrees lean of peak for long flights requiring max economy. I think you'll find that you can go to more than 50F lean to advantage = with a rotary on easy cruise (ask Tracy), and I found peak power to be more = like 100 F rich of peak. =20 So, I believe there is no such thing as "EGT too high". There is only = "peak EGT", whatever it is for your installation. High EGT can be symptomatic off other problems; incorrect timing is one. You'd also like to limit EGT to something less than about 1700 F to = avoid shortening the life of your exhaust system. =20 Al ------=_NextPart_000_0001_01C5507E.C404D6C0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

Given the fact that EGT for = a particualr engine/exhaust will vary slightly from = other identical engines as a function of "where the EGT sensor is placed = ", and stating at the start that we are talking about "cruise" power settings - not "full throttle at sea level" (in other words, = we are, by definition only talking about leaning at a lower power setting, with = proper timing and proper octane, where there is ZERO possibility of detonation) = isn't it true that if one adjusts mixture from rich to lean, that the EGT will "peak" at "best fuel-air ratio" for complete = combustion, and that max power will be achieved by richening a bit from that (richen = until you get max RPM for that immediate flight condition) which will result = in a slight drop in EGT? Then, if one leans back to "peak" = and then continues to lean, one will get "better economy", and, again, = EGT will decrease from what it was at "peak".

It seems you understand = correctly.

From reading of what = others have said, one can lean past "peak" maybe 50 degrees and have = a safe, economical cruise setting, maybe taking a slight increase in throttel or manifold pressure to keep HP up to what you want to cruise = at.

- The old Air Force BIG radial engines used to = cruise at 80 degrees lean of peak for long flights requiring max = economy.

I think you’ll find that = you can go to more than 50F lean to advantage with a rotary on easy cruise (ask = Tracy), and I found peak power to be more like 100 F rich of = peak.

So, I believe there is no = such thing as "EGT too high". There is only "peak EGT", = whatever it is for your installation.

High EGT can be symptomatic off = other problems; incorrect timing is one. You’d also like to limit = EGT to something less than about 1700 F to avoid shortening the life of your = exhaust system.

Al

------=_NextPart_000_0001_01C5507E.C404D6C0--