O2 Sensor Setpoints and Fuel Economy

[David-L]

Vehicle is 2017 Silverado 1500 5.3L-L83 6L80E.
Long story short here, looking for things in my tune that can be done to improve fuel economy some given the recent gas prices. I thought the O2 sensor setpoints might be a good place to gain a couple percent in fuel economy in the cruising areas without negatively impacting things too bad. Changed the O2 Sensor vs Airflow Mode table to 300 in the first 5 cells and sloping up to 450 in the last cell. Was all 450 across the board. Also adjusted the Min and Max Rich/Lean and Max Rich and Max Lean boxes accordingly. Or what I presume to be accordingly.

Drove it for a tank of gas to give things time to settle out and made a log on the drive home from work. To my amazement... things really haven't changed much and the average O2 sensor readings are nowhere near the setpoints. Maybe the changes I made don't do what I expected? Maybe the downstream O2 sensors have some effect on the fuel trims too?

I came to this conclusion by looking at the graph of O2 B1S1 and O2 B2S1 showing cell hits of 100 or more with the following filters to get steady state data only:
[50010.242]>180 and [50091.156]<70 and (abs([50090.156.slope(1500)])+abs([50090.156.slope(-500)]))<2 and ([4120.avg(1500)]-[4120.avg(-1500)])=0 and ([50091.156]<1 and [50020.114]>10)=0
Coolant Temp>180F, Accel Pedal<70%(to filter out PE), Throt Pos Chng<2%(to get steady state), Current Gear-Current Gear 1.5s prior(to filter out gear changes), Accel pedal NOT <1% and Vehicle Speed >10mph(to filter out idle and DFCO data)

I question the effect of the downstream sensor input because the cells where the downstream sensor is ~725mV or above, the average upstream sensor readings is much closer to the setpoints than the cells where the downstream sensor is below ~725mV.

So my questions are:
1) Does the downstream O2 sensor affect the fuel trims?
2) Is there anywhere to adjust the downstream O2 sensor setpoints?
3) Did I adjust the setpoints in a logical manner?
4) Is my data good and are my filters set up good?
5) What other areas of the tune should I look at for fuel economy?

[BigTuner]

1) No they are only used to confirm proper catalytic converter function
2) Not necessary
3) Changing the set points won't really make much of a difference, narrow band sensors are just that, very narrow, even at 300mv your AFR would be very close to 14.7 and if you change this substantially you will likely get some weirdness going on but doubt you will improve fuel economy much, your AFRs will likely just oscillate more erratically.

I think to have any chance of leaning out your fuel trims while cruising you would have to disable your O2 sensors and run full time open loop, or tweak your closed loop in some way to turn off while cruising. Once you are in open loop you could start fudging things, your stoichiometric values, your MAF calibration or VE tables etc. to lean things out, but this would make your airflow incorrect which will affect other things such as timing. There are probably ways to do this somewhat effectively this is just what came off the top of my head.

[kingtal0n]

1. Air fuel ratio won't have an enormous impact on economy, so none of the following is really worth your time and effort unless you are a fanatic about economy

2. You need a wideband to adjust air fuel ratio properly and tune an engine correct for all conditions. Narrowbands are essentially worthless because 14.7 is never a desirable air fuel ratio in a performance car, from the perspective of a tuning expert. Not for idle, cruise, or WOT. Never was

3. There are widebands out there with narrowband simulated output that are configurable. You can make 15.1:1 a 1.004volt signal and 15.5:1 a 0.044volt signal for example. Allowing retention of OEM closed loop while maintaining wideband lean cruise values.

4. You can alternatively design your own controller using Arduino, which can take a 0-5v wideband analog output signal and convert it to 0-1v narrowband signal if you program correctly. Or even make your own wideband setup.
https://controlduino.com/lambda-shield-01s00v00/
https://waltech.com/cszcms/wide-band...project-report

etc giving you full control over what the ECU can 'see' and even do to some extent.


5. Here are the tips for economy I write, most has little to do with air fuel ratio though. Running lean won't save a ton of fuel but it helps, every little thing helps. good luck
https://forum.hptuners.com/showthrea...l=1#post677442

[David-L]

Thanks very much for the feedback! I figured it wouldn't be a substantial savings by changing the AFR but I was hoping for a few percent savings at least. Perhaps that may be a bit optimistic of me. Buying and installing a wideband setup kind of defeats the purpose of this though, trying to save a little money. It would probably take a whole tanker load of gas before I would even break even by buying and using a wideband.

Thanks for the link to the other thread. Lots of good information in there. Added a little fuel to another idea I brewed up... just making sure the tune is done well and calibrating the MAF and VE tables well and running open loop all the time. That's basically what carburetors did really well for decades anyways, right? Surely it wouldn't be worse than that.

[kingtal0n]

A wideband is the only way to really tune an engine properly, fully, rapidly. Its worth its weight in gold for any performance app. I would never even consider driving a car (the kind of car I would drive, anyways) Without one

AEM wideband is < 200 authentic unit from AEM dealer on ebay, precious like water, it won't be a waste