Bank-to-Bank Tuning - How Do YOU Do It?

[rockystock]

Hey tuning gurus - NGC4 PCM, 392 Hemi here,

I'm seeing some pretty consistent bank-to-bank fuel trim differences - even when varying the cam position - and have been trying to tune them out. Here's what I've tried:

- Artificial Neural Network - Mult Bank to Bank: This one definitely works. In my setup, raising the multiplier above 1.000 will (comparing Bank 1 to Bank 2) make Bank 1 leaner; below 1.000 will make Bank 1 richer. Maybe the better way to say it is that the multiplier is applied to Bank 2, so when the multiplier is set to, say, 1.05, 5% more fuel is added to bank 2. The problem with this approach is that it appears to apply the multiplier everywhere (all engine RPM, all loads). Most of my fuel trim differences seem to vary mostly by RPM and somewhat by load (as seen by pressure ratio).

- Fuel - Open Loop / Base - Mass to be Delivered - RPM Mult Cyl#[1-8] - So far, I've tried adjusting the RPM Multipliers by a few percent. For bank-to-bank, I've simply modified all cylinders of a bank by changing all four cylinder tables by the same amount. I'm not sure if the changes are having any effect on fuel trims.

- Fuel - Open Loop / Base - Mass to be Delivered - Fuel Mass Mult Cyl#[1-8] - I have NOT tried messing with these tables because they allow adjustments according to "Mass Airflow" (anyone know what channel that might be for a Hemi with no direct airflow sensor?). I'm trying to go after the RPM-related differences before tinkering with these tables.

- Speed Density - Volumetric Efficiency - VE Bank 1, VE Bank 2: I know that tuning these tables independently will work, but I'm trying to get it done with the ANN and VVT enabled, so my VE tables are disabled.


That's all the levers that I know of to accomplish bank-to-bank tuning. Any of you experts know any tips or other ways to git-r-done? Thanks!

[HaasExp]

- Speed Density - Volumetric Efficiency - VE Bank 1, VE Bank 2: I know that tuning these tables independently will work, but I'm trying to get it done with the ANN and VVT enabled, so my VE tables are disabled.

This is the only way I have done it because I haven't come across a vehicle yet that has had a constant bank to bank fuel trim difference that could be solved by just a simple multiplier.
The bank to bank trim variations I've seen fluctuate between RPM and load cells.

[N2speed]

if you are getting that much of difference bank to bank then something mechanical is wrong..

[rockystock]

if you are getting that much of difference bank to bank then something mechanical is wrong..

How much are you thinking?

Most of my cruising VE range is less than 2%. Below ~1100 RPM the difference is around 3% and from ~3400 RPM to redline it goes from around 3% up to ~7%.

[PurpleRam]

How much are you thinking?

Most of my cruising VE range is less than 2%. Below ~1100 RPM the difference is around 3% and from ~3400 RPM to redline it goes from around 3% up to ~7%.

Stock 392 Intake ? .......3400-6000 4-5% is high side normal , that angled TB opening is not Ideal.,,,,,, are you running a Cold Air intake ? (just a curious question)

[rockystock]

Stock 392 Intake ? .......3400-6000 4-5% is high side normal , that angled TB opening is not Ideal.,,,,,, are you running a Cold Air intake ? (just a curious question)

Yeah this setup is interesting for sure. It's a 2008 Jeep Wrangler 4-door. I am running a snorkel into the stock air box - the snorkel definitely keeps the air cool. A couple of adapters into a 5.7 VVT truck intake, the short runner valves are functioning with an RPM window switch (I think, the difference is subtle at best). The intake end seems like it would be fairly balanced to me. The exhaust is where I suspect the differences are playing out: SRT manifolds to dual 3"; Bank 2 crosses over to the driver side with both banks going into an x-pipe. From there, the lines run parallel to the rear axle. The passenger side line then crosses back slightly to exit right-of-center, while the driver side runs relatively straight to a left-of-center exit.

My crackpot theory on my bank-to-bank differences goes something like this: at low RPM the banks' exhaust sort of collides at the x-pipe (Bank 2 has a longer path to the x-pipe so it sees maybe a bit more backpressure before mixing at the X); cruising RPM there is a bit of a bump in VE and good bank-to-bank balance which I think might be some positive scavenging going on; higher RPM the bank exhaust more or less shoots straight through the x-pipe, forcing each bank to stay on its respective side of the downstream pipe (and Bank 2 would have the overall longer path with the upstream crossover AND downstream crossover back to the right side of the jeep...).

Here's a bunch of photos of the setup minus the snorkel (I've since deleted the catalytic converters and re-hung the exhaust with better OEM hangers): https://www.jkowners.com/threads/sti...0/post-4468590

[PurpleRam]

Well the Eagle truck Intake manifold is fairly good side to side, soooo I'm going to say (purely a F---ing guess) check for vacuum leak.......or your theory( not as crack pot as you might think) has some merit.

[rockystock]

Well the Eagle truck Intake manifold is fairly good side to side, soooo I'm going to say (purely a F---ing guess) check for vacuum leak.......or your theory( not as crack pot as you might think) has some merit.

You know, this might be the reason I needed to finally drop the "catback" and let 'er rip. For science, of course.