Ccv to oil catch can

[O5BMW525]

Finally got smog done with stock ccv and will be putting oil catch can into car m54b25. Stock ccv system pretty much puts fuel trims around 0% with moderate blue smoke out the tailpipe. Oil catch can at full intake vacuum cuts down blue smoke somewhat but leans out fuel trim to +25% occasionally setting cel for bank 1 and 2 lean mixture but produces slight felt power. How do you guys correct this lean mixture?

[pbonsalb]

Are you using a vented catch can? If so, you have created a vacuum leak your fuel trims are compensating for. You don’t need a catch can if the pvc system is functioning properly. Your oil smoke out the exhaust is due to an improperly functioning stock system or other engine problems like failed valve stem seals or worn pistons/rings/bores.

Highly modded turbo motors can benefit from a catch can, but I would not install one on an M54. I use the stock one on my E61 535xi with N54 and JB4 without issue. I use the stock system on my modded E90 M3 without issue. I use a catch can vented to atmosphere (no vacuum attachment) in my E36M3 with fully built turbo S52.

[O5BMW525]

Non vented can. Likely worn rings and or seals

[pbonsalb]

Try a thicker oil.

[pshovest]

Properly installed catch can should not make fuel trims more positive. If they do change, then something in your installation caused it.

[O5BMW525]

Update

Oil consumption was 1qt every 1000 miles. After soaking cylinders with mopar upper engine cleaner overnight and adding a pcv valve inline with hose from valve cover to catch can due to seeing positive pressure above 2k rpm, oil consumption still there but has dropped from 1qt 1000 miles to 1qt 6000 miles. Hardly check oil level now.