On your datalogs, what do your O2's read? I am looking for someone with a supercharged lt1 that can give me there readings after going wot. I assume they are not used to give or take fuel away but will indicate if the car is rich or lean. Thanks in advance!

 

When you go WOT it'll go into open loop... correct.

Your narrow band O2 voltage is not very accurate for tuning a boosted engine. Invest in a wideband O2 that you can actually read real time AFR.
Tuning with a narrowband will get you in nothing but trouble.
For now target somewhere in the mid 800's AFR. which will be rich.
A narrowband is designed to operate in the .500mv range much higher or lower it's not accurate.
A wideband is what it sounds like...accurate over a much wider band of AFR.
Hope that helps,
Scott~

 

I agree with most of what is stated above about using a wideband sensor. As far as rich or lean, mid 800's AFR is not rich; 900+ is rich.

 

Mine are reading .890 to .900. Plugs look good and no detonation or pre-ignition. Knock retard counter is at 0.
Jim

 

I average 870's to 910's on the left side and 900's to 920's on the right. I have no know exhaust leaks so its suprising there is that much difference at wot. They are almost always 15-30 apart and any point of 100% throttle. Thats for the help so far. The wideband is a must it appears. I am still saving and shopping. There are so many choices and they are all expensive for my budget.

 

On a narrow band it should simply be very rich - you can't specifiy a number as the sensors are simply not accurate at the desired AF ratio, typically about 12.5:1 or richer.

Rich

 

If your Narrow bands are in that area at WOT it sounds like your close to being accurate to a narrow band's capibilitys. Back in the day tuning GN's we'd shoot for 780-830mv wot.
It's been years since relying on a narrow band for tuning.
Strange your getting rich on one side and leaner on the other. Could be from air swirling into the intake from a bend just prior to the throttle body.
You could make a screen just after the throttle body to even the air flow out and see if that helps. Just get some stainless screen and two throttlebody gaskets/rtv. Lightly RTV the gaskets and sandwitch the screen in-between. Put some weight on it over night. Cut out the excess screen and hole punch the bolt holes.
This seems to help streighten the airflow in a un-ballanced situation.
Make sure your throttle blades don't hit the screen just incase.
Air sure does weird things under boost. Might help...
~Scott

 

Split O2s have been around since the day they put two O2s in the system. Boosted or not. You can do alot of street tuning with Narrow bands but you should do the final with a wide band Your narrow bands can tell you alot and after all they ARE what the PCM fuels your car off of so I would not ignore them completely.

 

The PCM only uses the narrow band O2 sensors for part throttle conditions where it's trying to maintain 14.7:1 AFR; this is where the narrow band sensor is accurate.

 

Damn I knew I forgot Some thing on the last 50 LT1s I tuned...

 

Just to avoid misleading people who are new to this: the PCM primarily uses the O2 sensors in two ways. As implied above, when the car is in "closed loop" the PCM is actively using feedback from the O2 sensors to maintain 14.7:1. There are a number of parameters that must be met for for closed loop operation. Primarily the car has to have been running for a defined period (I believe stock is 90 seconds, but don't quote me on that), the coolant temp must be within defined parameters, and it must not be in "power enrichment" (WOT) mode. Second, the PCM learning strategy for setting long term block learns is based on O2 sensor readings. If it is consistently lean, the BLM's go up and vice versa.

However, as already stated, in PE mode the O2 sensors don't play an active role. The output is "ignored". There is still a signal from them. But due to the characteristics of the sensor itself, other than indicating a rich or lean condition, and quantifying it very roughly, the output is not usable for tuning except in the grossest sense. With a blower car, you expect at least ~850mV, indicating "very rich". Other than that, fuggedabout the sensor as a tuning aid. SOME people contend that the output of a given sensor is reproducible even at very low AF ratios. IOW, that they can "calibrate" the reading using a wideband and then use the output of the stock sensor for tuning their particular car. I would NOT risk a $5,000+ shortblock on this theory and would instead spend a few hundred bucks on a WB. Or go in with a coupkle of buddies and share one. Or get it professionally tuned (with a WB). Obviously, GM doesn't believe that the stock type sensor can be used except to indicate rich/lean, or they would have set up the PCM to run in closed loop at other than cruise conditions (see above).

Rich

 

Great answer. I was not really interested in tuning using them, but if there was an obivious rich or lean issue it might show up there. Thanks for your guys help again.