A bit of explination on their operation and how the SERT works with them...

2006 EFI Dyna models come equipped with 2 “switching” sensors…also known as stoichiometric sensors. Unlike wide-band sensors which can measure and control over a wide AFR range (10-20), switching sensors can only control within a narrow range (+/- 0.5 AFR). This offset in control is accomplished with the EFI Race Tuner by adjusting the Closed-Loop Bias table. Closed-loop operation is only used when the engine is in a normal operating condition. There are several instances when the ECM goes into open-loop operation. These include: warm-up, high load or high RPM operating conditions (such as WOT), when the vehicle is in Hot Engine Management, or any time the AFR requested is richer than 14.6. Data Mode has also been updated to read and record proper Closed-Loop parameters for proper tuning.

 

Question? So with the race tuner or ecm goes into open loop operation does it richen up more than the 14.6 ratio? I have a Thundermax but have wondered how the Screamin Eagle race tuner worked with the narrow band sensors. can you make it run richer than 14.6 ratio at say wide open throttle? thanks

 

The closed loop maps for the SERT cover only a certain range in closed loop mode. Typically from idle to about 4000 rpm up to 70 kpa map. Outside that range the AFR is set to values all the way down to 12.5 in the high load/rpm areas. In this operating mode, the SERT relies on correct VE data acquired by a correct tune.
In closed loop mode you can adjust the 02 sensor bias to get the AFR to about 14.2, very much the same idea IEDs pursue.