Greetings all! This is my first post.. I've been following this BITOG forum for many years as a guest...a tremendous wealth of knowledge on this forum! I've been searching the forums for over an hour and haven't come across anyone that's answered this issue adequately, and I'm thinking that this could be a solution for all S54 owners:
As the engine-builder's rule of thumb goes, one should have around 10 psi oil pressure per 1000RPM for standard bearing widths.
As we are all too familiar with, our rod bearings are narrower than the typical rod bearing found in cars.
One can then safely assume then that there's no way our bearings should be experiencing anything under 10psi/1000RPM, and, if anything, should be set to at least 12-14psi/1000RPM.
After taking a look at the TIS documents on checking oil pressure on the S54, it is clearly stipulated that there should be minimum 0.7bar (10.1 psi) at idle speed at operating temperature. It then goes to say that the pressure is then regulated to a constant 4bar (58 psi). This pressure is regulated by a sprung piston situated in the oil pump which limits the output pressure to a maximum of 4bar (58psi), (experts please step in and correct me if I'm wrong here).
At this point it becomes apparent that the bearings are under-lubricated at RPMs over 4800RPM (using a conservative guideline that 12psi are required per 1000RPM)
This makes me think that a far simpler solution to eliminate the rod bearing issues would be to remove the oil pump pressure regulator, or at least modify the existing setup to maintain higher oil pressures at the higher rpm.
1. Does anyone have experience with this or considered this?
2. Why would BMW fit a pressure regulator to the oil pump in the first place?
I just find it really bizarre how this could have been overlooked by the engineers in Germany, as this is the 101 of engine building, and I must be missing something...
As the engine-builder's rule of thumb goes, one should have around 10 psi oil pressure per 1000RPM for standard bearing widths.
As we are all too familiar with, our rod bearings are narrower than the typical rod bearing found in cars.
One can then safely assume then that there's no way our bearings should be experiencing anything under 10psi/1000RPM, and, if anything, should be set to at least 12-14psi/1000RPM.
After taking a look at the TIS documents on checking oil pressure on the S54, it is clearly stipulated that there should be minimum 0.7bar (10.1 psi) at idle speed at operating temperature. It then goes to say that the pressure is then regulated to a constant 4bar (58 psi). This pressure is regulated by a sprung piston situated in the oil pump which limits the output pressure to a maximum of 4bar (58psi), (experts please step in and correct me if I'm wrong here).
At this point it becomes apparent that the bearings are under-lubricated at RPMs over 4800RPM (using a conservative guideline that 12psi are required per 1000RPM)
This makes me think that a far simpler solution to eliminate the rod bearing issues would be to remove the oil pump pressure regulator, or at least modify the existing setup to maintain higher oil pressures at the higher rpm.
1. Does anyone have experience with this or considered this?
2. Why would BMW fit a pressure regulator to the oil pump in the first place?
I just find it really bizarre how this could have been overlooked by the engineers in Germany, as this is the 101 of engine building, and I must be missing something...