Date:         Tue, 27 Jul 2010 14:23:46 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: 2.1 VS 1.9 AFM
Comments: To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
In-Reply-To:  <001c01cb2d07$de94b620$6401a8c0@PROSPERITY>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 05:16 PM 7/26/2010 Monday, Scott Daniel - Turbovans wrote:
>sometimes if you look really carefully, and understand what they are
>representing in the drawings of the parts in the wire diagram .....they do
>try to represent what part is what inside a relay etc...
>so I am wonderiing if it means anything or not.

It's a slightly different drawing style, no significance.  In each
case the component on the left (arrow(s) not part of the wiring) is
the T-I sender, and the one on the right, with the heel of the arrow
incorporated into the wiring is the airflow sender -- the arrow
represents the wiper of the potentiometer.


>inputs to the ecu appear to be the same.
>I'm gonna pop a 2.1 AFM onto a digiget system and see what it does.

I'd be surprised if it didn't more-or-less work.  I'd also be
surprised if it got the mixture exactly right, though I imagine it
would be within the range that the lambda sensor could compensate for.


>if anyone would like to comment on the internal nuances of the two AFM's ...
>that would be great.

AFAIK the T-I senders are the same.  The pinout is the same.  The
resistor plate may or may not be the same but this is *probably* not
relevant since the output in either case is a (potentio-metered)
fraction of five volts based on vane displacement.  I'm making an
assumption I consider reasonable, that the output is linearly
proportional to angular displacement of the vane; however that is
subject to test.  If it's nonlinear then it *might* be differently
nonlinear between the two.  Since the 2.1 passes more air, I would
expect that the spring calibration would be "tighter" i.e. more air
for the same vane displacement.  That would make a 2.1 AFM run lean
on a 1.9 engine, no matter whether jet or fant; and conversely a 1.9
AFM run rich on a 2.1 engine.  Aside from that I doubt there are any
functional differences.

Yours,
David