dual lambda sensors

[Graydon D. Stuckey]

On Tue, 8 Aug 1995, Mattias Nyberg wrote:

> I've noticed that several cars have two lambda sensors, one
> before the catalyst and the other after. I've heard that one
> reason for this is to improve the closed loop fuel control.
> How does it work? What is gained by using the second lambda
> sensor? Isn't the oxygen that the first lambda sensor measures
> used up in the catalyst so there is no oxygen left for the
> second lambda sensor to measure?
Mattias,

	I have been told by a Ford calibration engineer that the second 
oxygen sensor is to measure catalytic convertor efficiency over long 
periods of time for the upcoming OBD-II requirements.  It also fine tunes 
A/F ratio a little, but the OBD-II is the primary reason.

Later,									
Graydon D. Stuckey								
graydon at apollo.gmi.edu								
'86 Audi 5000 CS Turbo Quattro, GDS Racing Stage 1
'83 Mazda RX7 w/13B, GDS Racing Stage 58474