X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 21 Jun 2012 13:07:35 -0400 Message-ID: X-Original-Return-Path: Received: from nm30-vm2.bullet.mail.ne1.yahoo.com ([98.138.91.130] verified) by logan.com (CommuniGate Pro SMTP 5.4.5) with SMTP id 5611612 for lml@lancaironline.net; Thu, 21 Jun 2012 07:32:24 -0400 Received-SPF: none receiver=logan.com; client-ip=98.138.91.130; envelope-from=casey.gary@yahoo.com Received: from [98.138.90.52] by nm30.bullet.mail.ne1.yahoo.com with NNFMP; 21 Jun 2012 11:31:48 -0000 Received: from [98.138.87.12] by tm5.bullet.mail.ne1.yahoo.com with NNFMP; 21 Jun 2012 11:31:48 -0000 Received: from [127.0.0.1] by omp1012.mail.ne1.yahoo.com with NNFMP; 21 Jun 2012 11:31:48 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 638799.85524.bm@omp1012.mail.ne1.yahoo.com Received: (qmail 81555 invoked by uid 60001); 21 Jun 2012 11:31:48 -0000 DomainKey-Signature:a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:In-Reply-To:MIME-Version:Content-Type; b=w5JFgq3ZyTkise4ujijcuzdRLlU4bU0hCXPh+A0OF1RAscdV97hPlAdshsgihvcj/HYW48YQNPS//5k4najtLwdbuWOoEpAxz2dJoPB7z3C35AsAMvpzM7xWgMPOaaeG0tVvXOhAoa3YwGXgP6IZCjxZccAHp0A91hfgeTAiTnM=; X-YMail-OSG: wS2v64EVM1lvF2zrIHQ5jTBpBQubwrKCdHrdyp77b6ydZZd fjd8ihKv2pGWDp7ahmpozj_NqkaDtUqXxFAqHspWisvUrr7QBrlBS7SZea1I _CSEVpbJLO53Ol9KRsGpO_O97cL9kNJAIIPQE8lj5cZw_tJVl6w7peSYA4qF oU9PQAkfaInR.RIqgJvckBqxnibZcnfRl3NiTYDRc4D.nYDvyLUTBQ6fdH9r uTqkjbp_SZndJiOs3ilTQ6eQXq7tnfI.AcE_slmYkJb1WVAqT1ZW_bbfCC6c 9LIXkw_I0grNm0jSlkpnF3KCiKY8Ot9FDnOnLaTvy49sIgLKGQETMF0K4IZa m93MGNDzxIzyFZBsGHYRqZ.TPF5ojsrwpmKG1hGEojUegRsndzwijbTrKgSo lkOpaYUEgXY3r3oD60oA9Uaqmq.a7p7mBX5s3JoKHK9NdsnLOXCxPJ2tItbE - Received: from [71.218.239.54] by web125606.mail.ne1.yahoo.com via HTTP; Thu, 21 Jun 2012 04:31:48 PDT X-Mailer: YahooMailWebService/0.8.118.349524 References: X-Original-Message-ID: <1340278308.79964.YahooMailNeo@web125606.mail.ne1.yahoo.com> X-Original-Date: Thu, 21 Jun 2012 04:31:48 -0700 (PDT) From: Gary Casey Reply-To: Gary Casey Subject: Re: Precision airmotive servo X-Original-To: Lancair Mailing List In-Reply-To: MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="607277540-140572633-1340278308=:79964" --607277540-140572633-1340278308=:79964 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Full throttle fuel flow is determined by only two things - the diameter of = the main metering jet and the pressure drop across it. =A0It is impractical= to mess with the pressure drop, so the only way to change the mixture is b= y changing (enlarging) the metering orifice. =A0Removing the brass orifice = is not very difficult - just remove the cap on the opposite end of the mixt= ure control. =A0It just slides out, but make sure it gets put back in with = the same orientation. =A0The orifice is off center and the mating port gets= rotated by the mixture control, closing off the orifice. =A0Pretty simple,= really.=0A=0ABut first you have to know how much you would want it enlarge= d. =A0The mixture at takeoff should be noticeably richer than best power - = if you lean at full throttle on the ground you should see a slight rpm incr= ease. =A0And yes, the EGT should be at least 150 ROP. =A0But what is peak E= GT on the ground? =A0Do you want to run it in that condition long enough to= find out? =A0You might want to richen in increments of 5 percent or less, = and therein is the rub. =A0To richen the mixture 5 percent the diameter mus= t be increased by only 2.5 percent. =A0If you are really lucky you might ha= ve a drill just that size - I did - but most likely you will have to take i= t to a shop that has reamers that can open it up. =A0The other thing to try= if you like is to put a radius at the leading edge of the orifice, which h= as a chamfer already. =A0A very slight "break" of the sharp edge will incre= ase the fuel flow a couple of percent. =A0Naturally, you have to keep every= thing perfectly clean. =A0The good thing is that you can test it without flying. =A0After = an attempt or two you will either have what you want or will be ready to se= nd it off to an "expert" for the adjustment. =A0You've "scrapped" the meter= ing orifice, but they're not very expensive.=0A=0AThe point is that for min= or increases in fuel flow you can make slight changes without much trouble.= =A0If you overshoot you are back to plan B. =A0The good news is that once = you have it right it never has to be adjusted again, unlike on the Continen= tal system.=0AGary Casey=0A=0AI believe my fuel servo is not delivering suf= ficient fuel to the engine in the takeoff position. Why I say this is becau= se the difference between the peak EGT and the takeoff EGT is 70 degrees F = on the leanest cylinder and 120 on the richest.=A0 The book says this sprea= d should be anywhere between 150 and 200 degrees F.=A0 Why do I care you ma= y ask.. Well my CHTs are too high at full throttle takeoff.=A0 I have to wo= rk to keep them below 430.=A0 I have done everything possible to maximize c= ooling airflow with little improvement in the CHT situation.=A0=A0=0A=0AAny= how, I would be interested in information from the group on the following= =A0=0A=0ALike to compare fuel flows at full throttle at close to sea level = (mine is between 15 and 16 gals/hr)=0AAny info concerning experience with e= nriching the takeoff flow on the bendix style RSA-5AD1 servo (this setting = is internal, I have found no reference material on the procedure)=0A=0AThan= ks=0A=0ATom --607277540-140572633-1340278308=:79964 Content-Type: text/html; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable
Full throttle = fuel flow is determined by only two things - the diameter of the main meter= ing jet and the pressure drop across it.  It is impractical to mess wi= th the pressure drop, so the only way to change the mixture is by changing = (enlarging) the metering orifice.  Removing the brass orifice is not v= ery difficult - just remove the cap on the opposite end of the mixture cont= rol.  It just slides out, but make sure it gets put back in with the s= ame orientation.  The orifice is off center and the mating port gets r= otated by the mixture control, closing off the orifice.  Pretty simple= , really.

But first you have to know how much you = would want it enlarged.  The mixture at takeoff should be noticeably r= icher than best power - if you lean at full throttle on the ground you should see a slight rpm increase.  And yes, the EGT should be at leas= t 150 ROP.  But what is peak EGT on the ground?  Do you want to r= un it in that condition long enough to find out?  You might want to ri= chen in increments of 5 percent or less, and therein is the rub.  To r= ichen the mixture 5 percent the diameter must be increased by only 2.5 perc= ent.  If you are really lucky you might have a drill just that size - = I did - but most likely you will have to take it to a shop that has reamers= that can open it up.  The other thing to try if you like is to put a = radius at the leading edge of the orifice, which has a chamfer already. &nb= sp;A very slight "break" of the sharp edge will increase the fuel flow a co= uple of percent.  Naturally, you have to keep everything perfectly cle= an.  The good thing is that you can test it without flying.  Afte= r an attempt or two you will either have what you want or will be ready to send it off to an "expert" for the adjustment.  You've "scra= pped" the metering orifice, but they're not very expensive.

<= /div>
The point is that for minor increases in fuel flow you can make s= light changes without much trouble.  If you overshoot you are back to = plan B.  The good news is that once you have it right it never has to = be adjusted again, unlike on the Continental system.
Gary Casey

Tom
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