OCBen

Well, correct me if I'm wrong here fellas, but it's generally understood that machined components, such as crankshafts and camshafts, though machined to be perfectly balanced, are not in actuality. These rotating components find their true centers during the wear-in (break-in) period. (In some engines - not necessarily Porsche engines - if you change the oil after a few hundred miles and examine the filter, you'll be able to see evidence of the wear-in by the glimmer of fine metallic dust particles collected by the filter.)

When these components wear themselves into their true centers of balance, the engine performs more efficiently. And with an increase in efficiency, an increase in output power is realized.

PV

That is exactly my confusion. I understand that the first miles will help to wear off the sharp edges, such that the rotating and moving parts in general starts to match each other. However, while those parts are rubbing and wearing and try to match each other, we take materials away, and that is exactly what you see in the oil, besides combustion products like water and for instance coke.

Now to the point: the wearing is not bringing the parts closer to each other. So although they start to match each other, the parts are starting to have more and more distance from each other, so can leak easier, create more friction in the gear box, etc, etc. So, I'm not sure we can expect a curve as described, or it must be that the friction between parts is reduced so much that they are initially decreasing faster than the incrrease of the gap.

I can be totally wrong, which I will accept if I see the statistics. So, I'm going to look for the statistics, if there are any any

Buzz911S

In my opinion, when you break in a car you're basically just seating the main bearings and seating the piston rings. Sure, there's some friction....but it isn't going to wear things as fast as you would think. The better the rings seat and seal, the more compression you get and the gain in horsepower is probably more relevant to that. Anything that has moving parts will wear in.....and usually over a period , that wearing in will peak....and from then on you're wearing "out". It's the nature of any machine.

OCBen

Well Grasshopper, let’s see if this might help a little. I'm not an engine designer but I am a mechanical engineer, and I DO know that engine components are designed so that they NEVER, EVER touch each other. They are designed to operate with a nominal gap between ALL components. And guess what is supposed to fill that gap? You guessed it - OIL. Machine components are designed to operate with a thin film of oil separating the components.

During the wear-in period those components that are not perfectly balanced are bound to violate that gap spacing and touch each other, hence the wear of which we speak. That is why it is critical not to super rev the engine during break-in because the not-yet-perfectly-balanced components will generate excessive centrifugal forces during high revs resulting in excessive wear of the components, resulting in excessive gapping, resulting in loss of power, resulting in premature ... you get the picture.

After the wear-in period, and all the rotating components have found their true centers, there should never, ever be any engine wear (theoretically), since these components will never, ever touch each other (theoretically) due to the protective film of oil separating them. Capeesh?

OCBen

I think you're right, the main bearings are primarily the target of "break-in". The main bearings, as you probably know, are journal bearings, which unlike anti-friction bearings that wear out over time and need to be replaced (e.g. wheel bearings), are designed to last a lifetime as they operate by riding on a layer of oil. After break-in, it's the oil that wears out from viscosity breakdown and is the only component of a journal bearing that is replaced over time.

Buzz911S

You can also "turn" a bearing in it's seat in the engine block by high revving, especially if you run it up too fast when it's cold. The main bearing doesn't have to move much to misalign the oil passages and....
Ruh Roh!

VikDiddy

There are no speed govenors, but there is a rev limiter. The car is able to go to 182 mph without any problems. After break-in you will believe it

PV

OK, I'm hopping along with your theoretical theory.

I watched my oil pressure closely over the first 6000 mile at idle and with warmed up motor. It took a while (maybe even 2500 mile) untill that pressure leveled off from initially 3.5+ barg, to currently 2.3 barg. After that, it didn't change anymore. Is that an indication, that the wearing in period was over? I lost a little pressure as the tolerances increased a bit compared to original. Due to that there is somewhat more leak and so less pressure build up.

Buzz911S

Dunno about that one. I'm no Porsche specialist... but in the first 750+ miles I've put on mine, the oil pressure stays pegged at the top of the scale. Maybe it will change as I put more miles on it.

1999Porsche911

I sure hope that none of my bearings ever touch each other....that would be instant destruction of the engine. The fact is is that there is clearence between all the engines moving parts and this clearance is filled by oil. Any moving part in the engine that does not have this clearance will be destroyed faster than you can turn the engine off.

PV

Look at the oil pressure when idle and warm.

PV

Bearings, yes, agree.

Carlos from Spain

My manual doesn't even mention the 4000RPM limit, the only reference to the RMPs during the 3000km brake-in is a vague "avoid high RMPs specially when engine is cold".

PV

Maybe they learned something with the tighter and tighter tolerances.