Date: Wed, 13 Nov 2002 14:55:17 -0500
From: Mark Denovich <mark@domain.elided>
Subject: Re: Subject: Re: 3.0 vs 2.5 V6 Throttle Bodies
Joe Elliott wrote:
Although others have claimed otherwise, it seems fairly obvious that the
AFM alone won't accomplish much, and my initial tests indicated that the
engine ran *very* lean if the AFM was the only variable changed (oxygen
sensor disconnected).
What exactly were you hoping to test? If you disconnected the O2
sensor, the ECU would use default open-loop fuel maps. If the BWM AFM
allowed more air flow compared to stock, the fuel map would certainly be
too lean. If anything you just proved that the BMW AFM does flow more
air. With the O2 sensor connected the ecu would compensate for the
additional air with additional fuel... presumably resulting in more power.
--Mark
The ECU goes into open-loop mode when the full-throttle switch is
closed, which is presumably when you want your performance upgrades
to do their job. While installing a big AFM and leaving everything
else stock (incl. oxygen sensor) might leave you with a car that runs
well at part throttle, the extreme lean running at WOT would counter
any performance improvement, I would think.