Date: Fri, 6 Jun 1997 09:37:02 -0700 (PDT)
>From: Erik C Peterson <n9541548@scooter.cc.wwu.edu>
To: kenneth d lewis <kdlewis@juno.com>
Cc: Multiple recipients of list <vanagon@lenti>
Subject: Re: O2 sensor question
Message-ID:
<Pine.ULT.3.91.970606093621.23470a-100000@scooter.cc.wwu.edu>

The O2 sensor is in closed loop while in startup and warmup, then it
goes 
to open loop after the sensor is at operating temperature.

Erik Peterson
Vehicle Research Institute

On Fri, 6 Jun 1997, kenneth d lewis wrote:

> 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.
> >
> >malc: 
hello a differ a bit ....
   Sorry when the engine is cold the hego sensor is not working and
ignore by the E.C.U {OPEN LOOP}

The E.C.U start to read the hego sensor when the hego is warm up]
and ecu can see a signal from the coolant sensor the engine start  
to warm up normaly the ecu gone wait until the hego voltage reach
over .6 volts on the hego

After come the close loop start to control the emission 
to keep the best mixture   14.7 to 1 {  strochiometric} something like
that, ouf big name.
At wide open throttle E.C.U ignore hego   you need power  not the time
to control emission

A.F.C or Vane air flow measure  cubic inch of air
 and you have  air temps sensor inside the vane  air flow 

to ckeck the barometic pressure you have two kind of sensors
 M.A.P   manifold absolute pressure  sensing the vacuum in the intake
 B.A.P   barometric presssure    outside the motor 
  some of those sensor are inside the ecu depend on the companie

  Mass sensor or hot wire type  calculate the densite of the air
  more the air is cold more oxygen you have, so you need more fuel
  more is hot less you  have oxygen, you  need less fuel 
  for the same cubic foot.
  this calculated by a cold wire and a hot wire
  some mass air flow have 200 degree  difference betwen those two wires
   The ecu always try to keep that 200 degree difference 
   so by the current it need to keep that difference the processor
know     how much air going inside the motor

bye 
Denis Belisle
quebec    

P.S if you see funny words do not laugh please I like better speak then
write  
Next time is gone be in french {joke}
I hope its gone help some people on the list .