Date: Thu, 16 Nov 2006 21:29:30 -0500
Reply-To: Dennis Haynes <dhaynes@OPTONLINE.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject: Re: AFM Data Requested
In-Reply-To: <Pine.LNX.4.58.0611161452130.27731@kenneke.com>
Content-type: text/plain; charset=us-ascii
The modern replacement for the AFM is known as a Mass Air Flow Sensor.
Instead of a flap it uses a heated wire and the circuitry generates a
voltage signal instead of changing the resistance. The main advantage is
reduced inlet restriction and signal relates flow and density, hence, the
term mass.
What are you really trying to gain? I doubt you can measure the power
increase on a water boxer and once the engine goes into closed loop
operation, the O2 sensor is the real driver for mixture control. In my
experience, I have actually found 3 bad AFM, 2 on the 1.9 and 1 2.1. They
were all opened and tampered with.
The data you really need is the voltage at various air flows. If you have an
open one and observe it with the engine running, you will find that it never
fully opens nor closes. It will move more with throttle opening than engine
rpm. The data points will need to be collected under varying loads. It may
be easier to replace it with a modified throttle position sensor and
circuit.
Dennis
-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
jon
Sent: Thursday, November 16, 2006 5:58 PM
To: vanagon@GERRY.VANAGON.COM
Subject: AFM Data Requested
I am deep in my research to find a "modern" replacement for the AFM. You
all out there could help me by measuring resistance of your AFM.
There are the data points I need (measured with an ohm meter, engine
off, AFM unplugged):
1) Engine off resistance (between pins 2 and 4)
2) Idle resistance (you can probably see a spot on the traces were idle
is)
3) Full "open" resistance
4) Half "scale" resistance (move wiper to half way on the tracks)
5) Vehicle year, type
6) Engine year, type (be sure I know if it's not a stock engine, etc)
7) Part number from your AFM (important)
This is not something for the faint of heart, so you need to know what you
are doing. Here is the procedure:
0) Make sure car is off, battery disconneted for good measure
1) Open up "hood"
2) Open AFM (black cover is "glued" on)
3) Unplug AFM
4) Get ohmeter, and connect to AFM pins 2 and 4(ground). A digital ohmeter
is recommneded.
5) Measure the above parameters
6) Put everything back together
7) Email me the results. ;)
I will post a spreadsheet with my findings.
Thanks,
Jon
