N55 has some oiling issues, just to name a few: - non-primary mains - weak block and girdle - varying oil flow - electonically the oil pressure is controlled based on the pressure after the oil cooler, while the mechanical back up is set up to work with the pressure of the mains, so once the leakage of the bearings become greater the pressure drops and the ECU has no way to see that, I believe it works with predefined leakage ratios, its worth mentioning that the temperature of the mains gallery is monitored and used to increase the oil pressure by some amount above 120 degrees, this high temperature target seems to be in for emissions/efficiency Few tweaks can be introduced here with potential to improve the reliability. 1. increasing of the bearing clearances and use of thicker oil 2. switching of the oil temperature and oil pressure sensor location, that way the ECU will monitor the bearing pressures directly 3. Lowering the coolant and oil temperatures 4. Adding additional external oil feed line from the filter to the bearings and smoothening the oil gallery corners, sharp edges are no good here due to the long path and the constantly varying flows 5. Strenghtening of the block girdle
Thread: f30.bimmerpost.com/forums/showthread.php?t=1840066
I said "fuel rail"; I meant oil rail.
Excelente aporte
N55 has some oiling issues, just to name a few:
- non-primary mains
- weak block and girdle
- varying oil flow
- electonically the oil pressure is controlled based on the pressure after the oil cooler, while the mechanical back up is set up to work with the pressure of the mains, so once the leakage of the bearings become greater the pressure drops and the ECU has no way to see that, I believe it works with predefined leakage ratios, its worth mentioning that the temperature of the mains gallery is monitored and used to increase the oil pressure by some amount above 120 degrees, this high temperature target seems to be in for emissions/efficiency
Few tweaks can be introduced here with potential to improve the reliability.
1. increasing of the bearing clearances and use of thicker oil
2. switching of the oil temperature and oil pressure sensor location, that way the ECU will monitor the bearing pressures directly
3. Lowering the coolant and oil temperatures
4. Adding additional external oil feed line from the filter to the bearings and smoothening the oil gallery corners, sharp edges are no good here due to the long path and the constantly varying flows
5. Strenghtening of the block girdle
My solution seems more direct.