On Tue, Dec 7, 2010 at 12:21 AM, David Beierl <dbeierl@attglobal.net> wrote:
> At 11:07 PM 12/6/2010, Larry Alofs wrote:
>>
>> David,
>> � Please clarify. �Are you saying that the mechanical inertia of the
>> vane is a good or a bad thing �Do you feel that the programming of the
>> ECU takes this inertia into account?
>
> I'm saying it's a good thing and corresponds to the accelerator pump in a
> carburetor. �When you open the throttle quickly, the air flow increases very
> rapidly and the inertia of the vane, which is fairly substantial, causes it
> to overswing somewhat. �This tells the ECU that there's more air going
> through the system than actually is, causing it to inject extra fuel, hence
> for that short interval a richer mixture.
>
> Since it's the AFM doing this and not the ECU, a MAF device would need to
> simulate the effect in some way, by monitoring rate-of-change of the airflow
> and increasing the signal to the ECU when there's a rapid increase in flow.
>
> Yrs,
> d
>

If one were to accept the idea that the overswing of the vane is a
good thing, The inertia producing it is still preventing the vane from
moving as quickly as we would like at the time the airflow is suddenly
increased.  Can't have one without the other.
  If the ECU got the info more quickly in the first place, the
over-swing and the over-enrichment would be less necessary.

  It has been my impression that the accelerator pump in a carbureted
system is, in part, designed to cope with the loss of vacuum when the
driver steps on the gas suddenly.  Less vacuum means less gas being
sucked thru the jets.

Larry A.