Fuel Trims - bank1 vs bank2

[coffee-3000]

I downloaded "TouchScan OBD Software" from Scantool.net to my laptop to check my long term fuel trims. I got 7 % on bank 1 and 10 % on bank 2. I wasn't expecting a valve for each bank. Is this telling me that cylinders 1,3,5 ( bank 1) are releasing less oxygen into the exhaust than cylinders 2,4,6 (bank 2 ) ? Or something like that ? It seems like bank 2 has to add more gas to air fuel mixture.

Is 7% and 10% within a normal range ?
Has anyone ever seen 0% and 0% ?

The software is pretty cool.
It great for a novice like me.
I'll post pictures soon.

Thanks.

[zppeacock]

Normal, usually anything plus or minus 15% is normal

[fenixus]

normal (in terms of engine specs) is +/-38% (outside of that range are error codes System Too Lean and System Too Rich).

considered normal on a brand new car would be +/-5%

considered normal on a used not so well maintained car would be +/-10%

ideally total fuel trims should stay within +/-3%, that's pretty much ideal.
total fuel trim is a sum of Long Term and Short Term fuel trim.

higher than 10% numbers may be an indication of some ongoing issue (resulting in distorted A/F ratio and ECU trying to compensate far before it trows a code).

[coffee-3000]

Thanks zpeacock and fenixus. This is great.