Return-Path: Sender: (Marvin Kaye) To: flyrotary@lancaironline.net Date: Fri, 06 Feb 2004 16:13:31 -0500 Message-ID: X-Original-Return-Path: Received: from turkey.mail.pas.earthlink.net ([207.217.120.126] verified) by logan.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 2979310 for flyrotary@lancaironline.net; Fri, 06 Feb 2004 14:16:52 -0500 Received: from user-2injqui.dialup.mindspring.com ([165.121.235.210] helo=Carol) by turkey.mail.pas.earthlink.net with smtp (Exim 3.33 #1) id 1ApBT7-0004OB-00 for flyrotary@lancaironline.net; Fri, 06 Feb 2004 11:16:50 -0800 X-Original-Message-ID: <008e01c3ece5$ae594de0$0000a398@Carol> From: "sqpilot@earthlink" X-Original-To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: nonEFI fuel systems X-Original-Date: Fri, 6 Feb 2004 12:51:33 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0067_01C3ECAF.F34D30A0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2720.3000 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2727.1300 This is a multi-part message in MIME format. ------=_NextPart_000_0067_01C3ECAF.F34D30A0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable [FlyRotary] Re: nonEFI fuel systems ----- Original Message -----=20 From: Ken Welter=20 To: Rotary motors in aircraft=20 Sent: Friday, February 06, 2004 5:55 AM Subject: [FlyRotary] Re: nonEFI fuel systems Hi, Ken....I also have been looking at the Weber carb. Without = going into full details, how difficult is it to add a mixture control to = the 48 Weber? Thanks in advance for your reply. Paul Conner There are two way to do it, one is with an air bleed system that = bleeds air form the intake to the float bole, this is what they use on = some snowmobiles and I have not tried this yet on a Weber. The system that I use is an air ram that changes the pressure = differential between the float bole and the Venturi. The ram tubes in this photo are positioned about 1.5 inches from the = velocity stacks, when the ram is closed the air is drawn only from the = air cleaner which is where the float bole vent is, when you open the air = ram it increases the air pressure on the Venturi's and the float bole = vent pressure that is in the air cleaner remains the same so it draws = less fuel. If I start opening the ram at cruise power setting setting the tac = will start climbing until it reaches perfect fuel mixture and then it = will start to drop as it goes in the lean side and for economy cruise I = drop the rpm about 100 rpm on the lean side, depending on altitude at = say less than 5000 ft if I open the ram wide open if will kill the = engine but at over 12,000 ft it can take all the air without killing it, = at 16,000 ft the ram will raise the tac 1000 rpm which is enough = difference between holding alt and coming down and I would have never = made it up there without the ram. One other thing about the Weber is that its very high tec compared = to crude aircraft or American carb's in that it is very adjustable and = it is very sensitive to pressure changes, if the air is thinner there is = less draw one the main jets so there will be less fuel drawn in. This can be adjusted for the particular engine and application by = changing the air correction jets and the emulsion tubes in relation to = the main jets, you can go to a smaller main gas jet and a smaller main = air and the mixture on the top end will remain the same but it will lean = the bottom end and mid range, the emulsion tubes mostly effect the mid = range. By jetting down to a smaller air correction jet and smaller main gas = jet makes it more sensitive air density and to be honest I don't think = the combination the I am currently running is the best as I only have = 100 hrs flying on the 48mm where I had 1000 hrs on the 51mm so I had it = dialed in much better Ken=20 Hi, Ken....thank you very much for taking the time to both explain = your system as well as provide the photo....It's true...a picture IS = worth a thousand words! Paul Conner =20 -------------------------------------------------------------------------= ----- >> Homepage: http://www.flyrotary.com/ >> Archive: http://lancaironline.net/lists/flyrotary/List.html ------=_NextPart_000_0067_01C3ECAF.F34D30A0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable [FlyRotary] Re: nonEFI fuel systems
 
----- Original Message -----
From:=20 Ken=20 Welter
Sent: Friday, February 06, 2004 = 5:55=20 AM
Subject: [FlyRotary] Re: nonEFI = fuel=20 systems



Hi, Ken....I also have been = looking=20 at the Weber carb.  Without going into full details, how = difficult is=20 it to add a mixture control to the 48 Weber?   Thanks in = advance=20 for your reply.  Paul Conner


   There are two way to do it, = one is with=20 an air bleed system that bleeds air form the intake to the float bole, = this is=20 what they use on some snowmobiles and I have not tried this yet on a=20 Weber.

 The system that I use is an air ram = that=20 changes the pressure differential between the float bole and the=20 Venturi.
 
 The ram tubes in this photo are = positioned=20 about 1.5 inches from the velocity stacks, when the ram is closed the = air is=20 drawn only from the air cleaner which is where the float bole vent is, = when=20 you open the air ram it increases the air pressure on the Venturi's = and the=20 float bole vent pressure that is in the air cleaner remains the same = so it=20 draws less fuel.

If I start opening the ram at cruise power = setting=20 setting the tac will start climbing until it reaches perfect fuel = mixture and=20 then it will start to drop as it goes in the lean side and for economy = cruise=20 I drop the rpm about 100 rpm on the lean side, depending on altitude = at say=20 less than 5000 ft if I open the ram wide open if will kill the engine = but at=20 over 12,000 ft it can take all the air without killing it, at 16,000 = ft the=20 ram will raise the tac 1000 rpm which is enough difference between = holding alt=20 and coming down and I would have never made it up there without the=20 ram.

 One other thing about the Weber is = that its=20 very  high tec compared to crude aircraft or American carb's in = that it=20 is very adjustable and it is very sensitive to pressure changes, if = the air is=20 thinner there is less draw one the main jets so there will be less = fuel drawn=20 in.

 This can be adjusted for the = particular engine=20 and application by changing the air correction jets and the emulsion = tubes in=20 relation to the main jets, you can go to a smaller main gas jet and a = smaller=20 main air and the mixture on the top end will remain the same but it = will lean=20 the bottom end and mid range, the emulsion tubes mostly effect the mid = range.
 
  By jetting down to a smaller air = correction=20 jet and smaller main gas jet makes it more sensitive air density and = to be=20 honest I don't think the combination the I am currently running is the = best as=20 I only have 100 hrs flying on the 48mm where I had 1000 hrs on the = 51mm so I=20 had it dialed in much better
  Ken 
 
Hi, Ken....thank you very much for taking = the time to=20 both explain your system as well as provide the photo....It's = true...a=20 picture IS worth a thousand words! Paul = Conner   

>>  Homepage: =20 http://www.flyrotary.com/
>>  Archive:  =20 = http://lancaironline.net/lists/flyrotary/List.html
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