Correct me if I'm wrong, but webers or mikunis use fixed ventury sizes whereas
the SU needle changes profile depending on amount of vacuum and air velocity.
How do they differ in maintaining correct air-fuel ratio when the fixed
venturi has one variable(air velocity) and the SU's have 2 (velocity and
needle profile)?
Steve
70' 1600
----- Original Message -----
From: Marcus A. Pryor
To: datsun-roadsters@autox.team.net
Sent: Tuesday, June 06, 2006 12:59 PM
Subject: Carburetion.
The first thing lost is velocity of the air stack. This brings in the
equation Bernouli's principle; that is, air pressure is inverse to speed.
Since a carburetor requires a venturi in order to create a vacuum and pull
fuel in, this creates a natural block to the air column. If that venturi
is too big, the engine will be severly hampered, resulting in erratic fuel
ratios.
Ideally, the CFM of a carburetor should take into account the uses of the
engine and rpm range. There are numerous methods used for this
calculation, and a simple Google search will find various formulas for
this calculation.
Marcus A. Pryor
For a new age of reason
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