When to go into Closed-Loop?

[Mazda Ebrahimi]

Thor Johnson wrote:
> 
> Ok... I have the Oxy sensors biased to ground (I figure I won't need that low
> reading) with a 1M resistor.  I was planning on going into closed loop as
> soon as I get >0.2V on the sensor.... any comments?
> 
>   How do the "big boys" know when to go into closed loop?
> 
>                 Thor Johnson

There is no rule set in stone for determining when to go to closed loop. 
 Most do it based on engine run time and coolant temp. at start-up (the 
warmer the engine at start-up, the less they wait).  However, this is 
not necessarily the best strategy (but its sufficient for their 
emissions controls).  Another strategy I have seen counts number of 
engine revolutions instead of time, so if you start the engine and 
operate it at high RPM, the system would go to closed loop faster than 
if you were just idling.  Yet others use calculated average mass air 
flow, and I think that's probably the most accurate method.  Remeber 
that going to closed loop does not necessarily mean better emissions if 
the catalyst is not up to temperature.

Also, almost all the systems I have seen have a simple diagnostic check 
that if the sensor voltage is too low or too high, they ignore the 
reading and stay in open loop.

Best Regards, Mazda