I'm missing something...

[Bruce]

MAP or MAF they are just used to calulate the air consumption of the engine.
Once you know how much air is being used, you can calulate how much fuel to
add to get a given AFR.

The only feedback on O2 is from the O2 sensor (exhaust side of the engine).
Ambient O2 levels vary from location to location, and that isn't directly
sensed for the fuel calulation.
Bruce


From: "Bob" <bob at scientist.com>
Subject: Re: I'm missing something...
> Isn't the reason for the MAP is to calculate the % Oxygen in
> the air at different elevations?
> MAF would still measure just the amount of Air entering the engine
>  , even if it's Oxygen content is much lower at higher elevations...
> or do I have it all wrong?

> From: "NickG" <nikog at mediaone.net>
> To: <diy_efi at diy-efi.org>
> Sent: Sunday, November 11, 2001 8:44 AM
> Subject: Re: I'm missing something...
> > 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


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