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Discussion Starter #1
I have read in some of the threads where some posters say "still running closed loop" or "not running closed loop"..

So whats that all about??

I would have thought that since the car has a closed loop system it would run in a closed loop mode all the time to maximise fuel ecconomy and power and minimise emissions..

Please someone explain..
 

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cars run closed loop at idle and part throttle. at high load/rpm they go open loop and run richer for max power and to prevent detonation. when in closed loop mode the fuel trims are adjusting, the trim values are still applied in open loop.
 

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On AEB 1.8Ts the oxygen sensor tries to maintain a leaner than stoichiometric condition at idle/part throttle to minimize emissions. Closed loop implies the oxygen sensor is influencing the fuel mixture.

At WOT, in open loop mode the ECU ignores the oxygen sensor (for max power).
 

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Discussion Starter #4
Ok.. So at WOT its open loop using a static map that is adjusted by the last "learned" trim values prior to going WOT..

Seems odd to me to do this.. Why not stay closed loop making it possible to cater for the various factors that effect the mixture requirements when running WOT and just program the ECU to maintain a slightly richer mixture during WOT periods?

I am sure there must be some reason for it that made them decide to do it the way they did.. :)
 

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Because earlier technologies with a narrow-band O2 sensor forced closed-loop to be 14.7:1. This will kill your engine at high rpm/load.

Newer cars with wideband O2 sensors can run closed-loop all the time, and the ecu adjusts to non-14.7:1 accordingly. IIRC the B6 is like this.
 

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Discussion Starter #6
Rusty said:
Because earlier technologies with a narrow-band O2 sensor forced closed-loop to be 14.7:1. This will kill your engine at high rpm/load.

Newer cars with wideband O2 sensors can run closed-loop all the time, and the ecu adjusts to non-14.7:1 accordingly. IIRC the B6 is like this.
That makes sence..

Thanks everyone for explaining it..
 
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