Malcom:
I beg to differ. I have a dash mounted LED (O2 sensor) monitor. I have
NEVER seen the system go into open loop once it reaches operating
temperature. In fact the higher the RPMs the faster the lean/rich cycles
occur.
>From the outer banks of North Carolina to the Smokies.
Ken Lewis
86 VW Transporter Three Door Pickup

 
On Fri, 6 Jun 1997 02:32:51 -0500 mholser@Adobe.COM (Malcolm Holser)
writes:
>since the O2 sensor is usually not in use when driving up high (^;
>You see, the system goes into an open-loop mode. bypassing the sensor 
>at  something like 3000 rpm and above. Then engines make so little power

>at altitude that you usually downshift and keep the rev's high.  The 
>airflow meter, which kinda measures air mass, kinda compensates.  I
understand 
>the hot-wire versions do a better job.
>
>In closed-loop operation (normal driving) the O2 sensor will do a good 
>job of controlling for optimum burn, including compensating for
altitude.
>
>malcolm
>