X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-m24.mx.aol.com ([64.12.137.5] verified) by logan.com (CommuniGate Pro SMTP 5.0.3) with ESMTP id 870289 for flyrotary@lancaironline.net; Fri, 09 Dec 2005 21:28:02 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.5; envelope-from=WRJJRS@aol.com Received: from WRJJRS@aol.com by imo-m24.mx.aol.com (mail_out_v38_r6.3.) id q.27.7fa797bb (15898) for ; Fri, 9 Dec 2005 21:27:13 -0500 (EST) Received: from MBLK-M23 (mblk-m23.mblk.aol.com [64.12.136.67]) by air-id09.mx.aol.com (v108.32) with ESMTP id MAILINID91-3e1a439a3d011e3; Fri, 09 Dec 2005 21:27:13 -0500 Date: Fri, 09 Dec 2005 21:27:13 -0500 Message-Id: <8C7CB485D5C5401-1AD8-15A2@MBLK-M23.sysops.aol.com> From: wrjjrs@aol.com References: Received: from 66.127.99.234 by MBLK-M23.sysops.aol.com (64.12.136.67) with HTTP (WebMailUI); Fri, 09 Dec 2005 21:27:13 -0500 X-MB-Message-Source: WebUI X-MB-Message-Type: User In-Reply-To: X-Mailer: AOL WebMail 15106 Subject: Re: [FlyRotary] Re: 48 Weber Content-Type: multipart/alternative; boundary="--------MailBlocks_8C7CB485D578F53_1AD8_1518_MBLK-M23.sysops.aol.com" MIME-Version: 1.0 To: flyrotary@lancaironline.net X-AOL-IP: 64.12.136.67 X-Spam-Flag: NO ----------MailBlocks_8C7CB485D578F53_1AD8_1518_MBLK-M23.sysops.aol.com Content-Type: text/plain; charset="us-ascii" I used to make a very good amount of money setting up Webbers for guys at the race shop I worked at. The little manual that is invaluable, a pamphlet really, was from Bap-Geon called simply "Tuning the Webber carburetor" The magic decoder ring, this book had a listing of air correction and emulsion tubes listed from rich to lean and where the cross over was. VERY HELPFUL as some are non sequential on DCOE's The main venturis being removable in Webbers you can get some odd combinations. I pulled a set off an E-Jag that had 2 different main and 2 different secondary (bullseye) venturis. Once all was put right the guy was so happy he almost cried! Make sure you have all the SAME parts for both sides first then start jetting! The payoff is that once jetted correctly and supplied with fresh fuel they are very reliable. Bill Jepson -----Original Message----- From: Lehanover@aol.com To: Rotary motors in aircraft Sent: Fri, 9 Dec 2005 21:05:14 EST Subject: [FlyRotary] Re: 48 Weber In a message dated 12/9/2005 2:39:15 PM Eastern Standard Time, downing.j@sbcglobal.net writes: Lynn; As mine is lying on the bench, I looked in and it has 42's. JohnD If Ken has 37MM venturies, his 200 mains will be on the rich side all through the RPM range. However, he injects nitrous for takeoff and may inject some additional fuel along with it. So richer is not hurting anything. The main jet controls all fuel entering from the float bowl. So, a change in main jet size changes everything from idle to top RPM. The emulsion tube takes air in through the air corrector jet and mixes it with fuel coming in through the main jet. How deep below the float bowl fuel level air is mixed with the fuel determines intermediate RPM performance. Lower holes make the fuel column lighter, and it will lift faster and flow out into the auxiliary venturi. (the big tube sticking out the center of the bore). The 42 MM venturies are about as big as you can go and still have any off idle performance. In other words, the venturi size controls how much vacuum will be available to draw mixture out of the lower end of the auxiliary venturi. The vacuum is called signal in carb talk. Smaller venturi = better signal. Bigger venturi=Worse signal. Once the engine is spooled up, none of this matters. Cruise RPM will just involve the air corrector, the emulsion tube and the main jet. The two big hollow screws between the bores are hold down screws. Use a big bladed driver to take them out. Pressed into the bottom of that screw is the emulsion tube. Hold onto the hold down screw and pull hard on the emulsion tube. (The brass tube with all of the holes). The screw comes off, and now you see the air corrector pressed into the top of the tube, and the main jet pressed into the bottom of the tube. There you are. That is the whole cruise fuel control system. A change of one main jet size is the same as two air corrector sizes. The F-7 emulsion tube is in the middle of the mixture range. The tubes and jets have the sizes (in MMs) stamped into them. Take the needle seat out and if that little screen is still in there, throw it away. The land area it sits on may be drilled out to 1/4" lest it be the main jet. I think you will like the carb. Not fussy at all. There is a gag for mixture control on the dyno, so you don't have to stop and change jets, and it involves making a cover for the well where the two sets of hold down screws live. The smaller ones are the idle jet holders. So you make a tall cover that can seal off this area. Install a 1/4" piece of brass tubing. Another piece of tubing stuck into the intake manifold. run them onto a "T" from the fish tank supply house. Install a needle valve in the run to the intake and one in the leg of the Tee. Now you can change mixture with the engine screaming. The more vacuum exposed to the air correctors the richer it runs. So you start off lean and control EGT with one of the needle valves. No rules about a needle valve on the dash board. As you go up, you adjust for more air and less vacuum. The engine leans out. Lynn E. Hanover ----------MailBlocks_8C7CB485D578F53_1AD8_1518_MBLK-M23.sysops.aol.com Content-Type: text/html; charset="us-ascii"
I used to make a very good amount of money setting up Webbers for guys at the race shop I worked at. The little manual that is invaluable, a pamphlet really, was from Bap-Geon called simply "Tuning the Webber carburetor" The magic decoder ring, this book had a listing of air correction and emulsion tubes listed from rich to lean and where the cross over was. VERY HELPFUL as some are non sequential on DCOE's  The main venturis being removable in Webbers you can get some odd combinations. I pulled a set off an E-Jag that had 2 different main and 2 different secondary (bullseye) venturis. Once all was put right the guy was so happy he almost cried! Make sure you have all the SAME parts for both sides first then start jetting! The payoff is that once jetted correctly and supplied with fresh fuel they are very reliable.
Bill Jepson
 
-----Original Message-----
From: Lehanover@aol.com
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Fri, 9 Dec 2005 21:05:14 EST
Subject: [FlyRotary] Re: 48 Weber

In a message dated 12/9/2005 2:39:15 PM Eastern Standard Time, downing.j@sbcglobal.net writes:
Lynn;  As mine is lying on the bench, I looked in and it has 42's.  JohnD
If Ken has 37MM venturies, his 200 mains will be on the rich side all through the RPM range.
However, he injects nitrous for takeoff and may inject some additional fuel along with it.
So richer is not hurting anything.
 
The main jet controls all fuel entering from the float bowl. So, a change in main jet size changes everything from idle to top RPM. The emulsion tube takes air in through the air corrector jet and mixes it with fuel coming in through the main jet. How deep below the float bowl fuel level air is mixed with the fuel determines intermediate RPM performance. Lower holes make the fuel column lighter, and it will lift faster and flow out into the auxiliary venturi.
(the big tube sticking out the center of the bore).
 
The 42 MM venturies are about as big as you can go and still have any off idle performance.
In other words, the venturi size controls how much vacuum will be available to draw mixture out of the lower end of the auxiliary venturi. The vacuum is called signal in carb talk.
Smaller venturi = better signal. Bigger venturi=Worse signal.
 
Once the engine is spooled up, none of this matters. Cruise RPM will just involve the air corrector, the emulsion tube and the main jet.
 
The two big hollow screws between the bores are hold down screws. Use a big bladed driver to take them out. Pressed into the bottom of that screw is the emulsion tube. Hold onto the hold down screw and pull hard on the emulsion tube. (The brass tube with all of the holes).
 
The screw comes off, and now you see the air corrector pressed into the top of the tube, and the main jet pressed into the bottom of the tube.
 
There you are. That is the whole cruise fuel control system.
 
A change of one main jet size is the same as two air corrector sizes. The F-7 emulsion tube is in the middle of the mixture range.
 
The tubes and jets have the sizes (in MMs) stamped into them.  
 
Take the needle seat out and if that little screen is still in there, throw it away. The land area it sits on may be drilled out to 1/4" lest it be the main jet.
 
I think you will like the carb. Not fussy at all.
 
There is a gag for mixture control on the dyno, so you don't have to stop and change jets, and it involves making a cover for the well where the two sets of hold down screws live.
The smaller ones are the idle jet holders. So you make a tall cover that can seal off this area.
Install a 1/4" piece of brass tubing. Another piece of tubing stuck into the intake manifold.
 
run them onto a "T" from the fish tank supply house. Install a needle valve in the run to the intake and one in the leg of the Tee. Now you can change mixture with the engine screaming. The more vacuum exposed to the air correctors the richer it runs. So you start off lean and control EGT with one of the needle valves. No rules about a needle valve on the dash board.
 
As you go up, you adjust for more air and less vacuum. The engine leans out.  
 
Lynn E. Hanover 
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