George,
The secondary venturi is there to provide enough vacuum when the flow is too low to pull fuel from the main jets. It's small diameter accelerates the flow enough to produce vacuum at idle and very small throttle openings.
Bill
------Original Message------
From: George Lendich
Sender: Rotary motors in aircraft
To: Rotary motors in aircraft
ReplyTo: Rotary motors in aircraft
Subject: [FlyRotary] Re: Weber chokes
Sent: Apr 4, 2010 2:13 PM

Bill,
What is the secondary for again?
George (down under)

> George,
> You are correct but remember the manifold efficiency is based on having
> the correct size runners to begin with. The venturi is needed to improve
> vacuum to draw fuel. The Weber has a secondary venturi as well, the little
> bullseye one in the middle. So things are complicated in any case. A well
> tuned FI is almost always better.
> Bill Jepson


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