Heated O2 sensor installed, re-tuning required?

Blower91 · 07-26-2005, 12:36 PM

I replaced the stock O2 sensor with a heated unit in my 91 Vette (long headers and cooler thermostat). After testing it I have some questions:

1) In my stock chip (AXCN) closed loop is entered above 50 deg C (122F), should I decrease this value a little bit now?

2) The new sensor makes a larger swing at part throttle. Old was roughly 150 to 800 mV and new is 50 to 850 mV. Expected?

3) Average BLM for every cell did not change much but max/min changed: 130/116 to 140/114, same thing with INT. Expected?

4) Voltage at WOT did not change much but output from old sensor was much smoother. Perhaps due to age and soot?

I would think the old sensor gave the ECM less accurate data (due to cooling off). The new sensor showed me that my tune was a little further off than I first thought… or should I draw some other conclusion?

ps How do you set HTML code "on" when you write a new post? Wanted to include BLM tables...

Alvin · 07-26-2005, 11:32 PM

Humm, interesting..

Are you setup to burn chips? If so start getting after those VE tables.

Blower91 · 07-28-2005, 07:11 AM

Quote:

Originally Posted by Alvin

Are you setup to burn chips? If so start getting after those VE tables.

Yes I am. Did a new chip and that put the BLM back to "normal".

I had a closer look at the data.

1) Like I said, when changing from non-heated to heated sensor the max BLM of the run went from 130 to 140. You can see the BLM cells here. It seems that only cell #2 was affected by the change, just minor changes for the others. Still I hitted the same region in cell #2 with the non-heated sensor run. In both cases INT eventually settled to 128 so I guess the ECM was happy with the BLM then. So do you understad why this happens?

2) The average O2 voltage at WOT increased a little bit with the heated sensor, see here. Also the PW increased so the engine did get some more fuel. When I entered PE the BLM was 120 in the non-heated case and 128 in the other. Is it possible that the ECM compensated for the slightly rich condition in the non-heated case? It does not quite add up when comparing to the PW though.

Thanks