[GarethK]

When you switch on o2 feedback on a Power FC is it then always aiming for lambda=1 when in 'feedback zone' or is it modifying the target lambda to suit your map settings?
i.e. if i set 3200rpm load cell 1/2/3 at 149% and have o2 feedback on, then hold the car at 3200rpm out of gear is it following my map and running 149% of predicted lambda=1 fuelling (+/- for some o2 feedback) or is it completely bypassing the map settings and targeting lambda=1 (i.e. theoretical 100%)??

 

[Toby Broom]

I think it only work when crusing, but I'm not sure sorry.

 

[GarethK]

You are right - It works at low load in general, whether it's cruising, idle etc, but it seems to me that since the lambda sensors are only narrowband sensors then for the o2 feedback to work it must be ignoring your map settings and cycling around its own lambda=1 target. This means that under 'cruise' conditions (say for arguments sake load cells <7) for o2 feedback to work properly using the std narrowband sensor your map setting will be irrelevant, whether 50% or 150%. I've got a wideband sensor / controller and logging (datalogit also on way!) so will find out but just wondered if anyone else knew.

 

[GarethK]

Doing a bit of searching around i think i've answered my own question. With o2 feedback on, the PFC 'targets' the base injection map only accessible with datalogit and not the hand controller 'trim' map, therefore when the ecu is using feedback loop control your hand controller map is not used.

 

[kismetcapitan]

must buy datalogit and figger out what the hell you guys are talking about...I hope to someday be able to tune my own PFC.....at least I now know the difference between narrowband and wideband lambda O2 sensors....still haven't been able to locate my stock narrowband sensor's location which is apparently somewhere after the turbos?

 

[ExScoobyT]

There is `no fuel map targetting` when you activate O2 feedback. As you correctly state it only operates on the feedback from the std hego sensor. Its purpose is to cycle the AFR very closely about 14.7, this is to ensure that the catalyst operates correctly.

It will only work if your base map is reasonably close to stoich fuelling to begin with. No cat fitted, you don`t really need it. It may help cruise / idle economy if your base map is out slightly. However IF it operates in the same fashion as an OEM system, it will try to hold stoich fuelling until quite a high rpm and load, this may be undesirable in terms of EGT and maximizing torque.

There is no other base fuel map with datalogit. The fuel map you can access on the controller is the same map you trim on the PC, albeit a damn site more user friendly.