07-11-2011, 01:36 PM
Join Date: Jul 2005
Total Cats: 68
How to test WBO2 response time / speed, and O2 feedback params
I turned off O2 feedback then:
Start engine, and hold revs at 5000 RPM, started datalogging, and while datalogging:
- increase fuel injector PW by +10% (in my AEM I did this with the overall fuel multiplier)
- decreased fuel inejctor PW by 10%
- repeat every 2 seconds or so
Examining the logs:
- at 5500 RPM my LC1 starts reacting about 180 ms after the injector PW changes
- after the initial 180 ms it then takes about 220 ms to rise (or fall) to the new O2 value
At idle the LC1 takes 500 ms to react and 700 ms to rise/fall. The latency is due to the engine operating parameters, not the LC1. This is also why you can't have closed loop O2 react very quickly at idle, and why ideally you want the O2 feedback speed parameters to be a function of engine airflow (i.e. RPM x MAP).
I compared a new sensor vs. my old one which had seen thousands of miles of oil burning, and surprisingly the old one was only marginally slower at the 5500 RPm test like 30 ms slower. Obviously at idle the difference is negligible.
An interesting observation is that with the new sensor the response shows ringing (like an underdamped PID loop), while the old one doesn't.