Date:         Fri, 6 Jul 2012 13:51:55 -0700
Reply-To:     neil n <musomuso@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         neil n <musomuso@GMAIL.COM>
Subject:      At Idle: AFM Flap, CO Screw Relationship. Explanation Found
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Hi all.

Was curious about the relationahip between the AFM air bypass and AFM
flap. Maybe someone else is too.

http://www.race.nangreaves.com/golf/FU01/ch7.6.html

From that page (Digifant II as used in other VW's but very similar to
the 2.1 WBX it seems):

"The idle mixture (% CO) is adjusted by turning the idle mixture
screw, changing the amount of air allowed to bypass the air flow
sensor flap. This changes the opening force acting on the flap, which
changes the potentiometer signal to the control unit. Since the
injector opening time (and therefore the amount of fuel delivered) is
influenced by the potentiometer signal, the idle mixture is changed."

Through my various stages of trouble shooting and learning about
Digifant on the 2.1 WBX, I had figured that the air bypass, at idle,
would allow the AFM to stay closed. e.g. that air bypassed this flap
and that the mixture was controlled by adjustment of air only, via the
CO screw. Not true it seems.



Neil.


--
Neil n

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