Question about widebands

[ChrisH]

Hi there,

I have a 2015 Sierra 5.3, and I just bought the MPVI2 and want to get started.

I?ve watched a number of YouTube videos, and the consensus is that I really need to use a wideband to get the most out of the tune.

I would like to use the tuner on my buddy?s truck as well, and so I am wondering if it is possible to only temporarily install the wideband in a factory O2 bung during logging and tuning. Then replace the factory sensor for normal use, I realize after every modification I would need to reinstall it to update the tune. I don?t particularly want to get a bung welded on, and as I said I want to be able to tune other vehicles.

If I go down this route, what steps would I need to take in order to tune? I?m assuming force Open Loop. Are there any SES/DTCs to disable? Do I leave the factory narrowband connected to its harness but loose, or should I remove it?

Many thanks!

Chris

[5FDP]

You could unplug the sensor if you wanted, it really doesn't matter that much. Having the o2 sensor trouble codes won't matter. Forcing open loop is exactly what you'd be doing, no closed loop, no fuel trims, no cat over temp or cat test/post o2 sensor test to skew the fueling.

Depending on what you are doing with the vehicle and what mods are done will depend on how you use the wideband to monitor the engine.

[cmitchell17]

I have been doing the same thing, however some weird stuff has been happening. I have read that you need to leave the codes reporting but you still need to force open loop with the closed loop voltage enable. For some reason my car randomly limited torque to around 70% TPS, and I believe it was some limp mode from having the drivers O2 sensor out.

Now that I have tuned VVE it seems to be running a lot better after installing my cam and heads. Long term trims appear to be working (obviously not the drivers side bank) since when looking at the log the PID is reporting a fuel trim percent. However short term trims are blank. None of the trims might actually not be working since I can see AFR jump around a lot though.

A lot of people say you shouldn't remove your stock O2 and run a wideband in place of it for whatever reason. I know using the wideband to try to tune VVE was hard since it seemed like the AFR was all over the place so you would have to hit certain cells for a long time so the erroneous values would average out. People may be saying don't remove the stock O2s because you should be doing VE tuning with fuel trims. I kind of agree and I'm going to try plugging the stock O2 back in and logging trims to try to get VVE a little better.

So I guess a wideband is only good for PE and WOT tuning, although technically you should be able to disable power enrichment and run the engine at WOT and get fuel trim feedback from the stock narrowbands to tune VE. A lot of people would freak out over this though because you would be running lean at WOT. Some stock truck tunes basically don't go into PE mode at WOT until after a minuet or so, so it seems like you would be fine for a second or 2. It could be a different story if you have high compression and are boosted, but still it seems way over blown. I think it's more dangerous to just increase timing without a Dyno or pressure sensor than to go lean at WOT for a few seconds. I think we should also be questioning that we are using AFR feedback to correct for airflow/airmass, to me AFR can vary depending on timing and other factors when airflow is constant.

[ChrisH]

You could unplug the sensor if you wanted, it really doesn't matter that much. Having the o2 sensor trouble codes won't matter. Forcing open loop is exactly what you'd be doing, no closed loop, no fuel trims, no cat over temp or cat test/post o2 sensor test to skew the fueling.

Depending on what you are doing with the vehicle and what mods are done will depend on how you use the wideband to monitor the engine.

Thanks for the reply!

So just unscrew the factory O2 from its bung, and disconnect it from the harness. Add the WB in its spot, and then follow your settings above?

Once I reinstall the factory O2 the DTCs should reset?

[jasonz28camaro]

The cable is long enough, couldnt you just get a holder and put it in the tailpipe like they do at the dyno if its temporary?

[5FDP]

Before the cat will get you far better readings. The exhaust gases would be going through 2 cats on a truck like his before it reached the tail pipe.

Many times I've remove the front o2 sensor, never really run into any problem. Once the weather isn't -20 to 30 degrees because winter is stupid, I will be trying to dial my truck in better for pump gas and E85.

[cmitchell17]

I've never tested this myself, but I would definitely think you would read extremely lean after the cat, that's the cats job is to force the rest of the unburnt fuel to combine with the oxygen. Modern engines emit virtually zero emissions, but the do gooders don't want anyone knowing that.