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      06-02-2013, 12:23 AM   #166

Drives: BMW M4 GTS
Join Date: Jan 2009
Location: Germany

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Originally Posted by BMRLVR View Post
Generally speaking, oil pressure does drop as oil clearance increases hence the reason why engines lose oil pressure if main and/or rod bearings are worn excessively.

20-25 PSI is lots of oil pressure at idle (40 PSI actually a fairly high number at idle) if that is even the number that the S65 engine would have at .002". I have never seen anyone test the oil pressure on an S65 with .002" main bearing clearance but would look forward to the numbers. As for your maximum pressure, that is going to be set by the system relief valve......... if the relief is at 80 PSI, once the pump makes enough flow to go over relief it will still achieve that same 80 PSI that you state, it may just take a few more RPM to get there........ the principles of hydraulics are universal pressure is the resistance to flow and more flow equals more pressure. Flow increases as the oil pump RPM increases(oil pump speed is tied directly to engine RPM) which is why there has to be a system relief to protect the system from overpressure since the oiling system on the S65 uses a positive displacement pump.

FYI: Dinan sets the main bearings to .0019" and the rods to .0025" on their strokers....... I obtained this information while shopping for a stroker! Obviously they see an issue with the tight OEM clearances and they don't see an oil pressure issue with adding a bit of clearance to the Mains and Rods since they use an OEM oil pump!

I can confirm that. When we were changing the rod bearings after 20.000km on my stroker and checked the clearance it was 0.063mm,