I’ve recently got my LC-1 installed in addition to my stock NBs (which are still feeding the PCM) but I’m seeing a 0.6 difference between measured WB and Closed Loop Commanded AFR and need some expert advice on how to dial my actual (measured by WB) in to my commanded.
I want my LC-1 range set between 10 and 18 AFR giving a voltage output of 2.95V (2.9375V) at 14.7. So I temporarily setup the LC-1 to output a constant 2.95V and after configuring the matching PID, I’ve logged the EIO input in a histogram so I could get a nice average but it’s not really needed since the LC-1/HPT combination is absolutely rock steady at 14.7 with the engine running or stopped. No offsets, ground loops or drifts – perfect, and a testament to the performance of both HPT and the often maligned LC-1 (many thanks to Bill, SoundEngineer and others for taking the time to provide quality advice!).
Next I decide to make some real measurements, so I re-program my LC-1 to output between 10 to 18, and fire-up the LS1. I have my closed loop stoich set at 14.68 and once C/L enables, I can log 14.68 AFR Commanded all day while idling in the driveway.
Problem is, my WB is showing me I’m getting an average 14.1 measured. Now, I know I’m trusting the WB to be totally accurate, but after a couple of careful free-air cals. it’s very repeatable and probably a lot better than the stock narrow bands.
My assumption is that the stock narrowband switching points are out causing commanded to deliver slightly rich and the voltages need to be tweaked. I’ve played around with these by +/- 50mV without making a great deal of difference – am I barking up the wrong tree? Any help appreciated...
Paul
Holden HSV GTS