Unbalanced fuel trims bank to bank

[wyattooearp]

Original mods on car , LS3 camaro, LT headers, LS9 cam, CAI.
After Whipple 2.9 twin screw install on car, Full whipple kit, came with Siemens Deka 63lb injectors, whipple tune with there injector data for the deka 63lbers, ZL1 pump and programmed FPCM with ZL1 settings.
Before install of whipple kit I dialed in MAF, car running in maf only, and o2 settings to eliminate surging with the o2 switching that was happening. Also adjusted min air flow for cam to tweak the idle a little bit.
Before whipple kit install, o2's switched together most of the time and fuel trims followed each other very closely at idle, light cruise , and acceleration. Within .5 to 1 percent bank to bank.
After whipple install I now see Bank 1 , (0 to -3 at idle) , and Bank 2 , (-6 to -9 ). In the scan they are never switching together and sometimes at light cruise are off bank to bank by 9-11 points.
It idles and drives fine but am worried about 1 bank running leaner than the other, especially if going into boost.
The IPW at idle is 1.1 to 1.3 ms side to side, same spread at light cruise. WOT the IPW reads within 2ms bank to bank usually both are the same, matching.
Smoked for vaccum leaks found nothing, no exhaust gaskets where touched during whipple install, plugs where whipple supplied denso IT22 gapped at 34, see an occasional miss show up on the scanner on different cylinders both banks ,random. Injectors, whipple supplied Deka 63lb with whipple supplied data.
Any opinions on the bank to bank fuel trim differences. Whipple PD blower issue? Deka injector issue? Install issue. Spark plug issue. 1.1 IPW too low effecting fuel feed?
Is this normal for a PD blower install for your fuel trims to go out bank to bank?

Any opinions would be appreciated.

Thanks

[mbray01]

A quick way to check if its the supercharger causing the issue, disconnect the bypass, so the valve stays closed. There is no real harm in doing this, just changes the airflow pattern in the intake portion of the blower. When the air enters the bypass portion it doesnt distribute properly and sometimes causes trim problems. The absolute worst one is "slp" superchargers, ive seen 30% variances with those, which causes massive blower surge. When you disconnect the bypass, it goes away, which shows you its an airflow problem

[wyattooearp]

OK, will try this. If its supercharger air flow issues I assume that there is no fix for this?

[10_SS]

Original mods on car , LS3 camaro, LT headers, LS9 cam, CAI.
After Whipple 2.9 twin screw install on car, Full whipple kit, came with Siemens Deka 63lb injectors, whipple tune with there injector data for the deka 63lbers, ZL1 pump and programmed FPCM with ZL1 settings.
Before install of whipple kit I dialed in MAF, car running in maf only, and o2 settings to eliminate surging with the o2 switching that was happening. Also adjusted min air flow for cam to tweak the idle a little bit.
Before whipple kit install, o2's switched together most of the time and fuel trims followed each other very closely at idle, light cruise , and acceleration. Within .5 to 1 percent bank to bank.
After whipple install I now see Bank 1 , (0 to -3 at idle) , and Bank 2 , (-6 to -9 ). In the scan they are never switching together and sometimes at light cruise are off bank to bank by 9-11 points.
It idles and drives fine but am worried about 1 bank running leaner than the other, especially if going into boost.
The IPW at idle is 1.1 to 1.3 ms side to side, same spread at light cruise. WOT the IPW reads within 2ms bank to bank usually both are the same, matching.
Smoked for vaccum leaks found nothing, no exhaust gaskets where touched during whipple install, plugs where whipple supplied denso IT22 gapped at 34, see an occasional miss show up on the scanner on different cylinders both banks ,random. Injectors, whipple supplied Deka 63lb with whipple supplied data.
Any opinions on the bank to bank fuel trim differences. Whipple PD blower issue? Deka injector issue? Install issue. Spark plug issue. 1.1 IPW too low effecting fuel feed?
Is this normal for a PD blower install for your fuel trims to go out bank to bank?

Any opinions would be appreciated.

Thanks

my 2010 LS3, 2.9 Whipple shows the same thing, -1, -2 on one side, -6-8 on the other. I recently put headers on, no change, same thing. The stock intake manifolds are made to run as good as possible, pass emissions, and this means close fuel trims. The Whipple.. well, it resembles nothing like the stock intake.. there are no real runners, it's just a big rectangle open area, designed to be pumped full of pressurized air, they care more about equal airflow under boost rather than light load cruising since they can correct the light load area with 02 sensors, they cant under WOT boost, it's not even monitored. This is one reason why they are run so rich, to account for the lean cylinders. Remember the Wideband or 02 sensor is averaging 4 cyl worth of rich/lean as it is. If the ECU see's it is adding fuel under normal conditions, it will add some under WOT, but that's as good as the correction gets.

I monitor 02 in the drivers side bank, I have the 2nd WB ready for the pass side, haven't installed it yet but I've been driving like this for 7? years, WOT every time I drive it, no problems. I do monitor knock in realtime via a little homebuild dash gauge when HPT isnt logging, which I don't really see anymore, so that is what is most important anyway.

They don't have to switch together, they are completely independent left to right based on the 02 feedback. Actually it runs smoother when they don't switch together since you have a noticeable power loss when they switch lean, when they both switch the same time you can actually feel it surging lightly on moderate accel, low rpm, out of PE fuel where 02's are switching, TCC locked if auto. That is due to the lean switching. All my cars have done it, most recent are 2016 5.3 Silverado, 2019 5.3 Silverado, 2020 Yukon 6.2.