X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 5.1.12) with ESMTP id 2308938 for flyrotary@lancaironline.net; Mon, 03 Sep 2007 12:49:18 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=eanderson@carolina.rr.com Received: from edward2 ([24.74.103.61]) by cdptpa-omta04.mail.rr.com with SMTP id <20070903164840.VUVP3980.cdptpa-omta04.mail.rr.com@edward2> for ; Mon, 3 Sep 2007 16:48:40 +0000 Message-ID: <002801c7ee4a$5533fed0$2402a8c0@edward2> From: "Ed Anderson" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Interface between Primary fuel rail and diffuser (air bleed) 20B Date: Mon, 3 Sep 2007 12:49:02 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0025_01C7EE28.CDE6B560" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.3138 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 This is a multi-part message in MIME format. ------=_NextPart_000_0025_01C7EE28.CDE6B560 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sorry, can't help you Joe. Just no experience with the 20B or 13BREW. But, I will mention this, IF you do have an air leak of any size, it = will be impossible to bring your idle down to low rpm. It will run = fine, but when you close your throttle, even a very small air leak will = leave your idle above 1200 rpm (or more). So I agree paying attention = to getting that correct is well worth the time and effort. =20 Ed ----- Original Message -----=20 From: Joe Ewen=20 To: Rotary motors in aircraft=20 Sent: Monday, September 03, 2007 11:32 AM Subject: [FlyRotary] Interface between Primary fuel rail and diffuser = (air bleed) 20B Background When installing the primary fuel rail on my 20B, I noticed a gap = between the primary fuel rail and the diffuser (air bleed.) One of the = original air bleeds was damaged when the rebuilder was removing. He = could not locate a replacement. He supplied new air bleeds designated = for a 93-95 13B, which he was informed were usable in the 20B. The gap = between the fuel rail and the diffuser seems to be between 0.110" and = 0.145". This measurement was determined by inserting the diffuser and = measuring its depth. Then the fuel rail was bolted in place. Through = the intake port, the injector was pushed up until it contacted the fuel = rail. The fuel rail was then removed and diffuser depth was measured. = The difference between the measurements was between 0.110" and 0.145". = The original diffuser returned by the rebuilder has no apparent seal, = the replacement has a rubber seal molded into the top. I took some measurements and drew up the primary, fuel rail / injector = /diffuser (see attached pdf.) It looks like there are 2 differences = between the diffusers that came on the 20B and the replacements recently = purchased. The height of the diffuser above the seating surface is much = lower on the replacements and the length of the area that projects into = the port/air stream is longer. The extra length extending into the port = is probably not an issue. =20 The shorter height of the replacement seems like it will be a problem, = the problem being a vacuum leak around the injector. A secondary issue = from a vacuum leak in this area may be an effect on fuel droplet size. = By looking at the injector, it appears that a metered amount of air is = intended to flow into the pintle cap, presumably to aid in reducing the = fuel droplet size. A vacuum leak in this area may reduce the air flow = through the pintle cap and the resulting droplet size reduction.=20 I would speculate that at medium or higher power levels the vacuum = leak would probably have little noticeable effect. I would expect that = the most significant effect would be at or near idle conditions. Since = smooth idle seems to be difficult to attain in many installations, it = would certainly be prudent to try and eliminate this issue (not to = mention that it would be good practice to get it right.) Questions 1. There seems to be a very small gap (~0.010") between the fuel rail = seating surface and the top of the original diffuser. It looks like = there should be a grommet that makes up the difference and provides a = positive seal. To anyone who has disassembled a 20B, is there a = grommet/seal the sits on top of the diffuser? 2. Same question as 1, for anyone who has disassembled a 93-95 13B = (13B-REW, I believe)? 3. Anyone have a source for the proper 20B diffusers? Any opinions and/or remedy suggestions are appreciated. Thanks, Joe -------------------------------------------------------------------------= ----- -- Homepage: http://www.flyrotary.com/ Archive and UnSub: = http://mail.lancaironline.net:81/lists/flyrotary/List.html ------=_NextPart_000_0025_01C7EE28.CDE6B560 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Sorry, can't help you Joe. Just no experience = with the 20B=20 or 13BREW.
 
  But, I will mention this, IF you do have = an air=20 leak of any size, it will be impossible to bring your idle down to low=20 rpm.  It will run fine, but  when you close your throttle, = even a very=20 small air leak will leave your idle above 1200 rpm (or more).  So I = agree=20 paying attention to getting that correct is well worth the time and=20 effort. 
 
Ed
----- Original Message -----
From:=20 Joe = Ewen=20
Sent: Monday, September 03, = 2007 11:32=20 AM
Subject: [FlyRotary] Interface = between=20 Primary fuel rail and diffuser (air bleed) 20B

Background
When installing the primary fuel = rail on my=20 20B, I noticed a gap between the primary fuel rail and the diffuser = (air=20 bleed.)  One of the original air bleeds was damaged when the = rebuilder=20 was removing.  He could not locate a replacement.  He = supplied new=20 air bleeds designated for a 93-95 13B, which he was informed were = usable in=20 the 20B.  The gap between the fuel rail and the diffuser seems to = be=20 between 0.110" and 0.145".  This measurement was determined by = inserting=20 the diffuser and measuring its depth.  Then the fuel rail was = bolted in=20 place.  Through the intake port, the injector was pushed up until = it=20 contacted the fuel rail.  The fuel rail was then removed and = diffuser=20 depth was measured.  The difference between the measurements was = between=20 0.110" and 0.145".  The original diffuser returned by the = rebuilder has=20 no apparent seal, the replacement has a rubber seal molded into the=20 top.
 
I took some measurements and drew up = the primary,=20 fuel rail / injector /diffuser (see attached pdf.)  It looks like = there=20 are 2 differences between the diffusers that came on the 20B and = the=20 replacements recently purchased.  The height of the diffuser = above the=20 seating surface is much lower on the replacements and the length of = the area=20 that projects into the port/air stream is longer.  The extra = length=20 extending into the port is probably not an issue.   =20
 
The shorter height of the replacement = seems like=20 it will be a problem, the problem being a vacuum leak around the=20 injector.  A secondary issue from a vacuum leak in this area may = be an=20 effect on fuel droplet size.  By looking at the injector, it = appears that=20 a metered amount of air is intended to flow into the pintle cap, = presumably to=20 aid in reducing the fuel droplet size.  A vacuum leak in this=20 area may reduce the air flow through the pintle cap and the = resulting=20 droplet size reduction. 
 
I would speculate that at medium or = higher power=20 levels the vacuum leak would probably have little noticeable = effect.  I=20 would expect that the most significant effect would be at or near idle = conditions.  Since smooth idle seems to be difficult to attain in = many=20 installations, it would certainly be prudent to try and eliminate this = issue=20 (not to mention that it would be good practice to get it = right.)
 
Questions
1.  There seems to be a very = small gap=20 (~0.010") between the fuel rail seating surface and the top of the = original=20 diffuser.  It looks like there should be a grommet that makes up = the=20 difference and provides a positive seal.  To anyone who has = disassembled=20 a 20B, is there a grommet/seal the sits on top of the = diffuser?
 
2.  Same question as 1, for = anyone who has=20 disassembled a 93-95 13B (13B-REW, I believe)?
 
3.  Anyone have a source for the = proper 20B=20 diffusers?
 
Any opinions and/or remedy suggestions are appreciated.
 
Thanks,
Joe

--
Homepage:  http://www.flyrotary.com/
Archive and=20 UnSub:  =20 = http://mail.lancaironline.net:81/lists/flyrotary/List.html
------=_NextPart_000_0025_01C7EE28.CDE6B560--