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-   -   Carrera Airflow Meter test question (http://forums.pelicanparts.com/porsche-911-technical-forum/624110-carrera-airflow-meter-test-question.html)

Tippy 08-11-2011 06:34 AM
Carrera Airflow Meter test question
 
Using the 9-volt battery test, in the first 5-10 degrees of travel, the voltage would not increase at all. Then, after I get past that point, the voltage would jump about 0.3 to 0.4 volts higher.

Is this normal or not?

aston@ultrasw.c 08-11-2011 09:45 AM
no, no jumps in voltage

a smooth and steady increase as the flap is opened.

Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk* ©2001 www.the944.com

Tippy 08-11-2011 09:53 AM
Quote:
Originally Posted by aston@ultrasw.c (Post 6190638)
no, no jumps in voltage

a smooth and steady increase as the flap is opened.

Air Flow Meter (AFM) - from "The 944 Motronic DME" by FR Wilk* ©2001 www.the944.com
So, I replaced the AFM with another one and my symptoms are still present. That is when I thought maybe the flat spot was intended at idle if you will.

aston@ultrasw.c 08-11-2011 09:56 AM
If you look at the curves in the AFM link, the shapes are slightly different but none have a .3V step.

This matches my experience.

Tippy 08-11-2011 09:59 AM
On the "1986 AFM map", there is a flat-spot in the first so-many-degrees.

That is where I am confused

aston@ultrasw.c 08-11-2011 10:01 AM
I have measured the actual AFM voltage with the car running at idle (by splicing into the wiring harness.)

The AFM voltage changes a small amount as the idle speed is adjusted.

aston@ultrasw.c 08-11-2011 10:04 AM
Quote:
Originally Posted by Tippy (Post 6190670)
On the "1986 AFM map", there is a flat-spot in the first so-many-degrees.

That is where I am confused
It may be flat but the transition is smooth, there is no step.

look how much the line would deviate for a .3V step

Tippy 08-11-2011 10:13 AM
Quote:
Originally Posted by aston@ultrasw.c (Post 6190680)
It may be flat but the transition is smooth, there is no step.

look how much the line would deviate for a .3V step
Ah yes, very true.

I guess I should look at the values a little more and not the curve.


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