X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from omr-d01.mx.aol.com ([205.188.252.208] verified) by logan.com (CommuniGate Pro SMTP 6.0.9e) with ESMTPS id 6808018 for lml@lancaironline.net; Mon, 31 Mar 2014 14:42:07 -0400 Received-SPF: pass receiver=logan.com; client-ip=205.188.252.208; envelope-from=Sky2high@aol.com Received: from mtaomg-mba01.mx.aol.com (mtaomg-mba01.mx.aol.com [172.26.133.111]) by omr-d01.mx.aol.com (Outbound Mail Relay) with ESMTP id 8F63670074DCA for ; Mon, 31 Mar 2014 14:41:31 -0400 (EDT) Received: from core-mlc005b.r1000.mail.aol.com (core-mlc005.r1000.mail.aol.com [172.29.188.211]) by mtaomg-mba01.mx.aol.com (OMAG/Core Interface) with ESMTP id 5EE0338000083 for ; Mon, 31 Mar 2014 14:41:31 -0400 (EDT) From: Sky2high@aol.com Full-name: Sky2high Message-ID: <25579.de63caf.406b10da@aol.com> Date: Mon, 31 Mar 2014 14:41:30 -0400 (EDT) Subject: Re: [LML] Re: EGT Probes To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_25579.de63caf.406b10da_boundary" X-Mailer: AOL 9.6 sub 168 X-Originating-IP: [24.14.166.87] x-aol-global-disposition: G DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mx.aol.com; s=20121107; t=1396291291; bh=ozXG4KJMtmpLfhvwjy57WmX2oy3BcMpyQxPOfDaf2L8=; h=From:To:Subject:Message-ID:Date:MIME-Version:Content-Type; b=dbPMep/r9YARhQsbfrNUlKik96ZmsIh0ibxwa6RCI23rouI8s9p8TSztdx8gLZfUA toDMhfnojCbWvGVWAv5tA0/kLEKbo09RijjQYN4rslSRmiKQglKzbOhra8gh6cWy4k gpUmhD21HYXd0jZfumxr6p+gHaNT5yhE6QH4yL3o= x-aol-sid: 3039ac1a856f5339b6db23f2 --part1_25579.de63caf.406b10da_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit Angier, Yes, the distance from the exhaust flange matters in absolute terms for EGT. Let's say they are all at 4 inches, then the absolute temps should be pretty close assuming zero difference in probes.. If they differ in location you may get quite different EGT readings. But, that is not important. In order for a balanced prop/engine to run smoothly, each cylinder should be producing the same horsepower. Thus, F/A mixture and ignition timing must be the same for each cylinder (along with good rings and proper valve operation). Also note that there is a hole in each injector body to allow air to be added to the injector stream to improve atomization. Also note that in NA engine setups there are pressure differences in the upper cooling plenum that may cause atomization to be different for each injector based on location. In turbo's engines, upper deck air at the same flow and pressure is fed to shrouded injectors so that the air distribution is equal and at a pressure higher than ambient upper cowl pressure. I.E. 30" MAP at 18000 MSL. But I digress. Well, suppose timing is fixed (or variable based on MAP and RPM) and air distribution is what it is (may be different at WOT or partial throttle - especially in carbureted engines). Then the thing that is possible to control is the fuel flow to each cylinder via tailored injector size. HP can be equalized this way. HP can be indirectly measured by fuel flow at peak EGT per cylinder (the GAMI test). Hmmmmm, maybe that's direct measurement. Anyway, if the FFs at peak EGT are different (say greater than .5 gph) then the cylinders are running at very different HPs, ergo not smooth. Personal note: If you have to get different flow injectors make sure you have performed the tests in conditions similar to cruise (but at 75% power or less) - where your smoother engine will spend most of its time, whether running ROP or LOP. Scott Krueger In a message dated 3/30/2014 9:38:51 P.M. Central Daylight Time, N4ZQ@VERIZON.NET writes: How far into the exhaust pipe should the EGT probe tip be positioned? When reinstalling my repaired exhaust pipe at KBQK, little attention was paid to the tip locations for #2&4 probes. This may be why I observed significantly different EGT temps compared to previous 'normal' flights. Does this make any sense? I would have thought that the distance from the exhaust valve to the probe tip would be the controlling factor. Angier Ames N4ZQ Up to my eyeballs in 1st annual. -- For archives and unsub http://mail.lancaironline.net:81/lists/lml/List.html --part1_25579.de63caf.406b10da_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: quoted-printable
Angier,
 
Yes, the distance from the exhaust flange matters in absolute ter= ms=20 for EGT.  Let's say they are all at 4 inches, then the absolute temps= =20 should be pretty close assuming zero difference in probes..  If they d= iffer=20 in location you may get quite different EGT readings.  But, that = is=20 not important.
 
In order for a balanced prop/engine to run smoothly, each cylinder sho= uld=20 be producing the same horsepower.  Thus, F/A mixture and ignition timi= ng=20 must be the same for each cylinder (along with good rings and proper v= alve=20 operation).  Also note that there is a hole in each injector body to a= llow=20 air to be added to the injector stream to improve atomization.  Also n= ote=20 that in NA engine setups there are pressure differences in the upper= =20 cooling plenum that may cause atomization to be different for each injector= =20 based on location. In turbo's engines, upper deck air at the same flow and= =20 pressure is fed to shrouded injectors so that the air distribution is equal= and=20 at a pressure higher than ambient upper cowl pressure.  I.E. 30" MAP a= t=20 18000 MSL.  But I digress.
 
Well, suppose timing is fixed (or variable based on MAP and RPM) = and=20 air distribution is what it is (may be different at WOT or partial throttle= -=20 especially in carbureted engines).  Then the thing that is possible to= =20 control is the fuel flow to each cylinder via tailored injec= tor=20 size.  HP can be equalized this way.  HP can be indirectly measur= ed by=20 fuel flow at peak EGT per cylinder (the GAMI test).  Hmmmmm, maybe tha= t's=20 direct measurement.  Anyway, if the FFs at peak EGT are different= (say=20 greater than .5 gph) then the cylinders are running at very different HPs, = ergo=20 not smooth.
 
Personal note:  If you have to get different flow injectors make = sure=20 you have performed the tests in conditions similar to cruise (but at 75% po= wer=20 or less) - where your smoother engine will spend most of its time, whe= ther=20 running ROP or LOP. 
 
Scott Krueger
 
In a message dated 3/30/2014 9:38:51 P.M. Central Daylight Time,=20 N4ZQ@VERIZON.NET writes:
= How far=20 into the exhaust pipe should the EGT probe tip be positioned?
When=20 reinstalling my repaired exhaust pipe at KBQK, little attention was paid = to=20 the tip locations for #2&4 probes.
This may be why I observed=20 significantly different EGT temps compared to previous 'normal'=20 flights.
Does this make any sense? I would have thought that the dista= nce=20 from the exhaust valve to the probe tip
would be the controlling=20 factor.

Angier Ames
N4ZQ
Up to my eyeballs in 1st=20 annual.



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