Hi All,

I am not an expert hence the following questions.

I was just wondering if the narrow band O2 sensors have to be removed to stop the narrow band O2 sensors creating a lean condition in closed loop mode. 

I believe the Delphi system with standard n.b. O2 sensors (in closed loop mode) forces the AFR to aprox. 14.6. I have been told the HD closed loop mode works at idle and below 40% static throttle position. Taking this into consideration, if you leave the O2 sensors connected wouldn't the bike still run lean, 14.6 afr?

If it doesn't, how does the TTS and SERT stop the O2 sensors forcing the ECM to lean out the mixture in closed loop mode?

Has anyone with a TTS recorded their afr's while in closed loop mode?

The ECM uses the o2 sensors to maintain a AFR around 14.6 (or what narrow range adjustment to the 14.6 AFR you want based on the bias you have set with the CLB) when in closed loop. I would not but if you want to turn off the sensors and not remove them, you could set your map cells in the AFR table to anything but 14.6. Going below 14.6 to say 14.5 - 13.5 will go richer. A value of 14.6 in your AFR table cells is what the ECM uses to switch the bike into closed loop. So setting any cell at anything but 14.6 will put the bike into open loop at that point in the map.

In other words, the ECU is looking to maintain a certain voltage from the O2 sensor by adjusting the fuel mix. You can set an offset in the voltage (CLBs) so that the ECU maintains a voltage corresponding to another AFR. You have a few tenths of an AFR available to play with before you go out of the sensor range, enough to have the bike run cooler. Off hand I don't recall the adjustment range, but I think 640mv bias corresponds to 14.64 and 852mv to 13.8. A bias voltage more than 780 is very hard on the sensor. Most have found 680 to 700 biases works very well.

Thanks for the info guy's. I was just curious how the TTS system got around the lean condition the narrow band sensors run.

I currently run a Thundermax at 13.8afr in summer and 14.1 to 14.3 afr in winter. We don't get much winter in Central North Qld.

I have a pro R hyper charger. 2 into 1 RB racing pipe on the 08 softail custom. The TM is not as economical as standard ECM and SERF but it runs better, smoother and less heat.

Thanks again,

Bluey