How long for 02 sensor warm-up for full accuracy?

[S351 R]

After start-up and idleing, coolant comes up to temp, even air is up to temp. Running in open loop and no other enrichment etc parameters should be playing a factor.

But with the same VE table AFR starts at 15.9, then seems to warm up, drops to 12's for significant time (10-15 mins) and then slowly starts getting leaner and leaner as if 02 sensor is just then starting to slowly get more accurate.

So, how long before the sensor is truly accurate? Trying to tune today is making me nuts.

 

[S351 R]

Further:
Is it possible that Air temp is affecting this? My table is set to 0 correction, but previous post from Craig say speed-density still does "something"?

My aluminum Vortech discharge tube where Air temp sensor is slowly gets heat-sinked up into the 140-170 range.

Would the speed density calculations be leaning things out as heat increases?

 

[bruce]

Originally posted by S351 R
After start-up and idleing, coolant comes up to temp, even air is up to temp. Running in open loop and no other enrichment etc parameters should be playing a factor.

But with the same VE table AFR starts at 15.9, then seems to warm up, drops to 12's for significant time (10-15 mins) and then slowly starts getting leaner and leaner as if 02 sensor is just then starting to slowly get more accurate.

So, how long before the sensor is truly accurate? Trying to tune today is making me nuts.

The sensor is warmed up in 30 secs or so.

Sounds more like your coolant temp and air temp corrections may need some attention.

Until the oil is fully up to temp., the AFR will seemingly wonder around some.

And then even the brew of the gas itself is a small factor.

 

[S351 R]

Thanks Bruce,
Well, CTS is 0 by 140 degrees, and ATS is zeroed accross the board.

So, although the sensor is accurate shortly after start, the motor itself could affect 02 readings as much as 2 pts (richer turning to leaner) up to 20 minutes later on temp alone. Coolant's up to 199 in no time, but I suppose it takes awhile for everything to get fully cooking like it usually is.

or, is maybe there something separate or mechanical I need to investigate? Would cat convertors/smog air pump be able to affect anything even if they are well back of the sensor?

 

[Craig Smith]

What you are experiencing is the reason why the VE table should only be tuned once *everything* is all the way up to normal operating temp. Even once the coolant is up to temp, the oil, the engine parts themselves, etc. are still developing temperature and these things will have an effect like what you are seeing.

The O2 sensor is warm and accurate within 30 seconds or so, I agree.

Air temp is part of the speed/density calculation. The ATS correction table is used in addition to what already happens "behind the scenes." Even if you have this whole table set to zero, variations in air temp still affect the fuel calculation.