[Diy_efi] MAP vs MAF

[Ken Young]

>The drawback to a MAP is that it only takes an average
>reading, and is time-delayed from hitting the
>throttle, so there's lag.  This is less the case with
>MAF, but there are still times you need to alter
>fueling RIGHT NOW based on changes in TPS, as the
>MegaSquirt people can tell you.  ;)

Where is the time delay for a MAP system?  At least on a turbo car, a MAF
measures the air relatively far from the throttle body.  Why wouldn't there
be more "lag" on a turbo MAF system, due to the extra time it takes the MAF
to compensate after the throttle changes?  Whereas the MAP and IAT sensors
are located near the throttle body.

While nobody is really arguing against MAF being better for a stock car, the
problem is that none of us have a stock car anymore.  And those of us with
turbos find out quickly that changing parameters leaves the ECU tables
pretty much obsolete and difficult to manage.  All those parameters that
made the MAF so flexible have made it difficult to keep up.  The MAF doesn't
know vacuum or pressure at the intake, and it doesn't know the true intake
temperature.  It has factory tables that it uses based on stock levels to
guess MAP and IAT.  

My assertion is that a modified turbo car with a stand alone system (or very
decent piggyback system) will be more capable with a MAP system.

Ken Young
'93 Eclipse GSX (not stock)

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