MAF vs MAP

[Darrell Norquay]

At 11:16 AM 6/5/96 -0400, you wrote:


>As for acceleration enrichment, we've entered a new arena.  Now
>we're discussing A/F ratio control, not measurement of inducted 
>air.  If the approach is to add additional fuel, without trying
>to measure air then calculate the amount of fuel (based on 
>measured air and desired A/F ratio), then why add a MAP sensor?
>The throttle position sensor is already there.  Am I missing a
>benefit of MAP-based enrichment over throttle-based enrichment?

>Anthony Tsakiris

Ah, but you forget - throttle position does not have a direct relationship
to engine load.  You can have different manifold pressures with the same
throttle
position under varying engine loads.  Thus, the MAP would be giving valuable
information that the TPS could not.  This may or may not have a drastic
effect on mixture demands, but I'm betting that it would sure affect
driveability and fuel consumption.  This may explain why some MAF based
systems have MAP sensors. 

An additional benefit that I want to point out for the use of MAP sensors in
MAF-based systems is for ignition advance calculations.  This would need to 
be modified for engine loading as well, which a MAF alone could not.  Knock
sensors could be used in place of the MAP for this, however.  I guess it all 
depends on which one is cheaper for the OEMs.


>(Should I still be adding these definitions.  I recall a past discussion.)

Why not?

TPS - Throttle Position Sensor

regards
dn