Originally Posted by MaD
Thank you sturovo!
Can you tell us how to regulate the variable resistors?
Initially when wiring up the circuit the voltages are set and typically do not need further adjustment.
The way I set the voltage is to start the car and turn the screws on the variable resistors until the desired voltage is achieved measuring with a multimeter to ground. (To make setting the o2 clamp value easier I added a test point to a spare terminal which is not shown on the diagram.)
Once set, the voltages are fairly consistent each time the car is run as the system voltage doesn't change that much. (You can record the TPS signal on EMB and compare the setting on different runs to verify that circuit gives consistent clamp voltages.)
The 0.34 volt signal for the o2 clamp corresponds to around 12.5 AFR cruise on my car. (Lower clamp voltage gives richer AFR, higher gives leaner AFR.)
If using autotune the TPS clamp voltage should be set so that the additional fuel injection map does not react when the o2 clamp is not active. In my case the 1.02 volt signal corresponds to to around 57% of TPS scale ((1.8-0)/1.02*100). (For wideband autotune these figures would be different.)
Even if not using autotune it is a good idea IMO to bring it to EMB TPS as it enables boost AFR data logging.
In my experience Autotune works well with larger than stock injectors and lower (7 psi) boost levels. The o2 clamp voltage sets a decent 12.5 AFR to start and the TPS map adds more fuel as the o2 signal leans out and is able to react in time to hold good AFRs.
At higher boost autotune struggles to keep up with rapidly changing conditions because of the nature of the feed back loop. On a gradual pull at higher boost autotune can provide real good information for mapping. (I was able to quickly build 90% of my higher boost map in this way.)
The way I have my autotune set up is that it corrects by adding fuel on lean o2 signal. I may try it the other way, subtracting fuel on rich signal.