[KingLT1]

Originally Posted by pavetim

How do you turn off VVE so o ly it runs im MAF? I disabled my ltft, o2 sensors although the one i disconnected for the wb gave an engine light, disabled dfco, dusavked car protection. What else am i missing? My stft are still active, in fact the one passenger side is where i used the wb in place of the stock o2 and its pulling 26% stft

by changing the dynamic airflow rpm threshold.

[pavetim]

Pretty sure i did that too. Does the stft still work if thats disabled? Ltft are off but stft still correcting

[KingLT1]

The only time fuel trims are not used is when the ECU is in open loop. Closed loop fueling relies on MAF and o2 data to trim the fuel to achieve stoich.

[pavetim]

Then why do you disable O2 sensors when tuning maf?

[KingLT1]

I don't disable o2's for closed loop maf tuning. I log maf vs LT fuel trim for part throttle and log Maf vs wideband error for PE tuning then adjust the maf accordingly.

[Joshinator99]

Originally Posted by pavetim

Then why do you disable O2 sensors when tuning maf?

Originally Posted by KingLT1

I don't disable o2's for closed loop maf tuning. I log maf vs LT fuel trim for part throttle and log Maf vs wideband error for PE tuning then adjust the maf accordingly.

Agreed, same here.

[6spdhyperblue]

X3

[pavetim]

Now i am confused. If you use o2 sensors and ltft for tuning your maf then its not maf only, you are using the sensors to make adjustments. Then how do you know your mad is tuned properly if the sensors keep making fuel trim corrections

[KingLT1]

Originally Posted by pavetim

Now i am confused. If you use o2 sensors and ltft for tuning your maf then its not maf only, you are using the sensors to make adjustments. Then how do you know your mad is tuned properly if the sensors keep making fuel trim corrections

Maf only means that you are not using VVE or dynamic airflow modeling for fueling adjustments in Open loop PE mode only.

When not in PE mode(closed loop),which is used for idle and part throttle conditions, The ECU still relies on the MAF and O2's for fueling control to achieve stoich via fuel trim adjustments. When you dial in the MAF there will be less fuel trim correction needed. Ideally you want to be between -5 and 0. If you are outside that window then you adjust the MAF until you get in that range in your part throttle cells.

Now when you go WOT the ECU enters PE mode(open loop) and only references the MAF for fueling above the rpm you set the dynamic air flow cutoff. Most MAF only tunes disable Dynamic Airflow above 1000rpm. This is where you need to log a Maf error vs wideband afr histogram because o2's and fuel trims are not used for fuel correction.

If you set dynamic airflow to let's say 6000rpm the ECU would reference both the VVE and MAF for fueling up to that rpm.

If you force the ECU into SD mode(Speed Density), then it won't use the MAF at all and rely on VVE for all fuel correction. The issue with this(albeit a minor issue) is that when the weather changes your fueling will change, that is why GM uses MAF sensors because it can correct fueling for temperature and air density change in both Open and Closed loop.

Hopefully that clears things up for you.

[pavetim]

Oh ok then i guess i need a bung welded in my exhaust? Cause i just took out a pre cat o2 and used my wideband in that spot. In that case i might need cat delete pipes cause there is no room for another o2 sensor in my 2017 ss. Probably why i was getting 22% stft on that bank

[pavetim]

I have room after the primary cats for a wideband but there is a big debate about that. I seen a guy on YouTube, australian guy forgot his channel but he said he has tested before the cat and after and the afr difference is so tiny it doesnt matter. Opinons?

[KingLT1]

I was always told to keep the wideband in front of the cats but I have not tested that theory. I have a bung welded into one of my CA cat delete pipes. You could grab a set of delete pipes(two sets for sale right now in the classifieds) and have a bung welded in and bolt those in place of the factory cats. This will make your exhaust louder.

[pavetim]

Then would i have to delete the secondary cats too, maybe taking too much heat since primaries do most of the work?

[Joshinator99]

Originally Posted by pavetim

Then would i have to delete the secondary cats too, maybe taking too much heat since primaries do most of the work?

Nope. I believe King is still running his primary cats (and making good power too).

+1 on putting the wideband O2 before the cat too.