Originally Posted by mr.sentra_specv
OK well i have a VE setup running off a calum basic board and i am in the initial stages of tunning it. at idle i have some slight issues. first off after a few seconds usually 5-10 the stock o2 sensor hits about .83-.85 and sits there the afr drops slightly from 14.7-.15.1 down to 13.9-14.1 at about the same time the ignition timing drops from 15 at the ecu side down to 7-11 deg. i have the actual base timing set to 15 deg confirmed by timing light. so i am not sure what i should do as timing and AFR maps show the correct values but it looks like the ecu pulls some other info after the car sits at idle in neutral for a few seconds.
I don't see anything to be concerned about in your description of how your car is behaving.
Both my cars (B13 DE and VE) also demonstrate this change in idle AFR, but mine do it after 20 to 30 seconds. The AFR richens a point or two -- it's very predictable, and it happens with Calum, JWT, and B13 OEM ECUs. In the DE, it seems to be associated with activation of the AIV, so my hypothesis has been that there is some residual trigger that has been carried forward in the Calum and JWT ECUs like some bad DNA. Nothing to worry about, and I don't know how to fix it.
Many times at idle, the narrow band will read either rich or lean for extended periods of time. Hold the RPM at 2500 to 3000 and observe the behavior of the narrow band O2 sensor read out. It should flip back and forth, rich to lean, every couple seconds. If it does, you are good to go. If it does not, then your mixture is way off or your O2 sensor is not working properly. All of this assumes that your ECU is set up for closed loop operation.
Setting your timing to 15* -- both physically and in the ECU just means that this is where the ECU starts from when it comes to idle timing. Unless you are in Set Timing Mode, the ECU will constantly adjust timing and AAR settings to keep your idle speed close to spec. If you put the car in Set Timing Mode, your timing will read 15* on your computer regardless of the physical setting (which you have to set with a timing light) and it will be rock steady.
Here endeth another overly long post -- hope it's helpful. Please respond if I have missed something.