Official S65 Bearing Specification/Clearance Wiki

[Scharbag]

Originally Posted by PaulGros

I'd say they're both relevant.

Firstly I'm struggling to see how bearings can give extra clearance when the measured and published figures put the wall thickness inline with OEM / others?

So that then raises the question on why there is an oil flow difference, particularly on an engine with a controlled pump that varies flow? As far as I am aware, the oil pressure and flow data was measured in total, not just for the bearing feed. So, if I am going to be pedantic, that then also raises the question of how you know the oil flow to the bearings was lower when only total engine flow was measured?

Flow is a function of pressure and system curve. Just like V=IR in electrical.

By changing clearance, the system curve is also changed (resistance analog). The S65 has a variable displacement oil pump with a pressure pilot. This allows the pump to maintain a target pressure as system variables change. Therefore, if "resistance" is reduced, flow must increase.

Yes - this is a single engine but a single variable was changed. Given the data, the only conclusion is that the BE bearings changed the system curve by reducing the resistance to flow. This means that the BE shells have more clearance than the 702/703 bearings that were removed from the engine.

I agree, the "proper" way to "prove" this would be to test a statistically significant number of engines. Realistically, this is impractical given the massive cost this would require. What we can do is extrapolate and infer given the results that we do have access too. If there is data that exists to contradict the existing thesis that the OE shells doe not offer proper clearance, then that needs to be considered. That said, theory and practice are often different - so given the data that is available regarding measured cranks, rods and shells, I will happily defer to practice and results rather than arguing about the theory.

Finally - why in the heck would any engine manufacturer produce an engine with a SINGLE rod shell? That puts ALL your eggs in the tolerance basket... Lame.

Cheers,