after market airflow meters

[Jason R. Haines]

> At 10:25 PM 3/21/01 -0500, you wrote:
> >> how do aftermarket airflow meters increase HP?
>
> By fooling the A/F ratio and by reducing restriction to airflow.

The fooling the A/F part is often where the most gain is achieved with
changing to the aftermarket MAF's (at least in the applications we have
seen) but also poses the most risk because the ECM no longer has accurate
control of the AFR and can sometimes go lean at WOT. The reason a gain can
be seen on a stock ECM/PCM is because the factory usually targets AFR's of
11 to 12 at WOT to protect the catalysts (and in some boosted applications
targets even richer AFRs). The ECM no longer having the proper MAF
calibration can cause the WOT AFR to be leaner (we have seen some of the
aftermarket MAF's lean the cars out over 2 full ratios). The big problem can
be if the ECM is commanding leaner values (for example, not yet in PE or
modified calibration with leaner WOT AFR's already), then the AFR can be too
lean and cause detonation, spark retard and potential engine damage. We have
seen this on the chassis dyno on several vehicles.

Just my $0.02


Jason


----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org