I did a bit of OBDII graphing last night while my wife drove the car back from a short road trip. She isn't used to driving it so her throttle modulation was not the best.


Closed loop O2 sensor readings bounce between close to 0mV to about 800mV. The frequency must be relatively high compared to the scan rate of the logger because the graph looks horrid.

The most interesting thing that I noticed was that the O2 reading were steady, behaving like open loop control, with anything over about 25-30% throttle. I thought open loop control only came into effect during WOT. Hmmmm......? [scratches head]

O2 voltage drops to 0mV and stays there when off throttle.

I was affraid to ask her[for safety reasons] to drop it into 4th and do a WOT pull to redline. I really wanted to watch the O2 reading to see what it would do.


Timing seemed to follow throttle positon, only the opposite direction. Timing went to about 6 degrees @ 2700RPM and WOT. Hovered around 35 during 70MPH cruising.

 

That sounds about right according to some of the tuning instructions I've seen, the low point recommendation is about 35%.. Considering in closed loop mode, the SAFC settings would essentially be cancelled out by the ECU's learning..

I would expect the timing to be different under load, and under WOT, as compared to part throttle cruising.. Not certain if those are good or not considering I haven't been tracking timing from when my car was stock.. at least you arent noticing sudden timing changes that could indicate knock...