I'm missing something...

[NickG]

A flapper door AFM can not compensate for changes in air density. The AFMs
are 'airflow meters', but not 'mass airflow meters' like the current mass
air meters. Thus, changes in elevation are not detected. That is why the car
in question started running rich at higher elevations.

But, I would have expected the ECU to tempensate and adjust the mixture
based on the O2 sensor's feedback. Unless, of course, the system is
programmed to run in open loop or has adaption turned off.

Nick
'95 M3 turbo

> I was riding in a guy's supercharged car and we were driving up the
> mountain.  When we got to the top, we had gained ~5000ft in elevation.
Half
> way up, his car started to run very rich, according to the "tip of the
nose
> AFR sensor."  I would expect this, of course, except:
>
> This car is equiped with a flapper door AFM which I've been told are self
> compensating for air temp and elevation.  This made sense at the time
since
> I believed that the air's MASS was opening the door to the AFM.  As the
air
> got hotter or thinner, the door wouldn't open as much at a given RPM and
the
> ECU would be able to compensate.


----- End of forwarded message from owner-diy_efi at diy-efi.org -----
----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org