Cavitation wear in journal bearings

[Bill_W]

There was a thread that was closed that brought up cavitation wear on bearings. Thought it was an interesting subject and found this.

https://www.sciencedirect.com/science/article/abs/pii/S0301679X16302109

 

[ZeeOSix]

"Cavitation has been found to increase with increase in viscosity and speed–the effect of speed being more dominating [23]."

So race cars could all have damage to journal bearings due to high RPM. Grocery getters ... not so much if any.

Like said in the other threads ... anyone here ever see cavitation damage on journal bearings with their own eyes? I never have, even on motorcycle engines that rev to the moon with pretty thick oils.

 

[ZeeOSix]

Also, oil feed pressure from the oil pump helps to mitigate cavitation by keeping the low pressure side of the bearings at a higher pressure. Higher the pressure, less likely there will be cavitation. Higher pressures are always seen at higher RPM, which is the right direction since cavitation can happen easier at higher RPM.

Side note - speaking of PD pumps, my response to your comment from the other thread, it is not normal for non-variable PD pump to go into pressure relief at 2000 RPM unless the oil was super cold and thick. When at operating temperature, most car's oil pump will not go into pressure relief even at redline - my Z06 wouldn't. If you're talking about a variable displacement pump, they could be change the output volume at 2000+ RPM by design and the output control logic, not the pump hitting relief like a normal old fashioned PD pump.

https://bobistheoilguy.com/forums/t...ar-with-20-wt-oil.362786/page-14#post-6355909

 

[Bill_W]

Also, oil feed pressure from the oil pump helps to mitigate cavitation by keeping the low pressure side of the bearings at a higher pressure. Higher the pressure, less likely there will be cavitation. Higher pressures are always seen at higher RPM, which is the right direction since cavitation can happen easier at higher RPM.

Side note - speaking of PD pumps, my response to your comment from the other thread, it is not normal for non-variable PD pump to go into pressure relief at 2000 RPM unless the oil was super cold and thick. When at operating temperature, most car's oil pump will not go into pressure relief even at redline - my Z06 wouldn't. If you're talking about a variable displacement pump, they could be change the output volume at 2000+ RPM by design and the output control logic, not the pump hitting relief like a normal old fashioned PD pump.

https://bobistheoilguy.com/forums/t...ar-with-20-wt-oil.362786/page-14#post-6355909

Thanks Zee… agree everything is variable when that pressure relief happens (temperature?). My neighbor had low pressure oil and we looked into a different spring to increase the overall oil pressure on the oil pump rebuild. It did not work when we increased the spring pressure. He ended up selling the Denali. Modern variable oil pumps are a vast improvement.

What I found interesting was the 10% gas dissolved in the oil that can develop a vapor for cavitation.

 

[OVERKILL]

Thanks Zee… agree everything is variable when that pressure relief happens (temperature?). My neighbor had low pressure oil and we looked into a different spring to increase the overall oil pressure on the oil pump rebuild. It did not work when we increased the spring pressure. He ended up selling the Denali. Modern variable oil pumps are a vast improvement.

If it was an LSx, was probably the pick-up, they tend to leak and drop pressure, regardless of the relief pressure of the pump.

 

[Bill_W]

If it was an LSx, was probably the pick-up, they tend to leak and drop pressure, regardless of the relief pressure of the pump.

An SUV but we never really went further than that. I explored changing out the bearings since he did a lot of towing.

 

[ZeeOSix]

What I found interesting was the 10% gas dissolved in the oil that can develop a vapor for cavitation.

Yes, oil aeration (air bubbles in the oil) can also impact cavitation. On my motorcycle it has a glass oil level sight window on the side of the engine, and I can look and see if there is any major oil aeration going on. I don't seem much if any. Obviously, way too high an oil level can cause excessive oil aeration, and oils are formulated to help combat "foaming" which is essentially aeration.

 

[Jetronic]

Motorcycle oils have even higher emphasis on anti-foaming than car oils. Race oils more than pcmo etc....

 

[OVERKILL]

An SUV but we never really went further than that. I explored changing out the bearings since he did a lot of towing.

Right, but I mean the LSx family of engines (LS1...etc), they have a tendency for the oil pickup tube o-ring to harden and then they suck air, dropping oil pressure. If you replaced the spring but not the o-ring, that characteristic wouldn't change.

 

[Cujet]

Cavitation damage to a rod bearing is sometimes associated with severe detonation.

 

[Cujet]

anyone here ever see cavitation damage on journal bearings with their own eyes?

Yes, as mentioned above, severe knocking.

 

[ZeeOSix]

Yes, as mentioned above, severe knocking.

Which isn't normal engine operation.