O2 mV swing, how much is normal?
O2 mV swing, how much is normal? I'm trying to smooth out my fueling at idle and part throttle.
Could someone tell me what range is normal for O2 mV output?
I get 15mV to 980mV with occassional railing at the bottom that may last for 2-3 cycles before oscilating again. Is this swing accross the entire range 0-1V normal or good? Is it better to reduce that swing and tighten it up?
Could someone tell me what range is normal for O2 mV output?
I get 15mV to 980mV with occassional railing at the bottom that may last for 2-3 cycles before oscilating again. Is this swing accross the entire range 0-1V normal or good? Is it better to reduce that swing and tighten it up?
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
that's normal... you can tell a good O2 by how fast it switches... the plotted out graph should look like a crazy sine wave, up down up down
The O2 sensors switch rich lean rich lean to try to maintain 14.7:1
The O2 sensors switch rich lean rich lean to try to maintain 14.7:1
The graph I get is half sine half square with chatter. I was able to reduce the low mV clipping by raising up the O2 switch point.
I reduced idle proportional fuel settings, but resulting mV were hardly noticable.
Can you send/post me a log/screen shot with good O2 characteristics so I can see what a good one looks like?
I reduced idle proportional fuel settings, but resulting mV were hardly noticable.
Can you send/post me a log/screen shot with good O2 characteristics so I can see what a good one looks like?
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
This is one of my car right after putting some brand new Denso sensors in
On initial startup it won't look like this since you start in open loop... and when you have more throttle (I think 44% or 64% is when PE turns on) it'll command a richer AFR
But when in closed loop commanding 14.7 AFR it should switch pretty fast
I guess mine doesn't really look like a sine wave anymore... my stock O2s would look more like a sine wave, switch high, still high but less mv, less mv, switch low, low low, w/the Denso's the switch rate is really fast
On initial startup it won't look like this since you start in open loop... and when you have more throttle (I think 44% or 64% is when PE turns on) it'll command a richer AFR
But when in closed loop commanding 14.7 AFR it should switch pretty fast
I guess mine doesn't really look like a sine wave anymore... my stock O2s would look more like a sine wave, switch high, still high but less mv, less mv, switch low, low low, w/the Denso's the switch rate is really fast
Image quality is crap, but check out the red and blue traces at bottom. This is idle 830rpm. It looks the same at idle 1000 rpm also. Could this be improved? Or is it good enough?
They're plenty fine, as long as they are in oscillation, they are doing a narrowband O2s job.. I did not quantify the changes, but by raising or lowering the O2 switch point (mV) I have centered the signal better. At first I thought the O2's were bumping off the bottom when at idle 'cause the cam overlap was getting them wet. I slowly raised idle to 1500 rpm and nothing changed. Still bumped off the 10mV mark. But raising the switch point did make a slight difference.
The problem is figuring out which airflow mode is being used.
How does that airflow mode table assign values? Is it based on cyl dyn air in g/min?
I was playing around with idle proportional fuel last night. It didnt effect O2 amplitude at all. It may have slowed down the frequency.
The problem is figuring out which airflow mode is being used.
How does that airflow mode table assign values? Is it based on cyl dyn air in g/min?
I was playing around with idle proportional fuel last night. It didnt effect O2 amplitude at all. It may have slowed down the frequency.
