Quote:
Originally Posted by deansbimmer
No, it is a fact that in normally operating engines the most bearing wear occurs at startup. Wear is occurring to the bearings until oil pressure builds which produces the hydrodynamic bearing that the crankshaft rides on during operation. Under oil pressure this fluid bearing prevents the physical contact between bearings and journals.
In addition to every startup, engines with unfavorable tolerance stacking from the factory are hit with the double whammy. Its why we see "babied" engines fail just like those that are tracked. How the engine is treated only speaks to a portion of how the bearings will wear.
You can read about how engine bearings work here:
http://kingbearings.com/files/Engine..._They_Work.pdf |
For sure, hence the "not really" comment.
Yes, the majority of "wear" occurs at startup, because the hydrodynamic bearings are not yet operating under pressure. BUT, on a properly designed engine, that wear is soooooo minuscule that we might as well ignore it. If that were not the case, then my buddies 32 year old E30 city commuter would be a paperweight cause he starts that damn thing at least 10 times every day!!
Now, if you drive a cold engine hard right after startup, then that is a recipe for additional wear, and a good hard slap.
By no means am I disagreeing with you sir. You know far more about engines than I do. I do think it is important to clarify that the normal startup "wear" would never cause a rod bearing to look like some that have been pulled from S65 engines. The issue with the S65 is that under load, and at higher RPM, the rod bearings are NOT operating as a proper hydrodynamic bearings.
Cheers,