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Arouse the DAMPFHAMMER!
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Arouse the DAMPFHAMMER!
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@LotusElise What would cause this?
This is well developed pitting of a tribolocial surface. Pitting's root cause is decomposition of material in the surface by either chemical mechanism like corrosion attack or mechanical stress like valve bouncing. The range of examples for both is huge. An oil forcing chemical effects like corrosion is possible, lack of oil is possible.

The position of max. intensity, the oil layers location and the roller surface give me the impression of a worn surface plus a chemical attack by e.g. an oil additive and maybe condensed humidity. The exhaust cam wear came across on the ECO versions several time here. Seems they run a proper Hertzian pressure on the lift side as well with an lack of fabrication quality, introduced by wrong oil formulation induced corrosion attack.

E.g. austenitic steel suffer much on chlorine ions, especially if the corrosion protecting chrome oxide layer is deformed and cracked under higher hertzian pressure and chemical attack. A higher content of Molybate and Tungstun in the oil formulation can reduce the chemical corrosion effect as it works out like an inhibitor. Both are not ingredients of every engine oil.
 

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Arouse the DAMPFHAMMER!
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I thought of talking about a common basis 🤭. Sorry for that and thanks for clarification of it.

The tribological surface is the result of the surface interacting with the environment. This interaction can take the form of a metal interacting with the environment to form oxides, nitrides, or hydroxides. Interaction with environments other than air can produce different surface films.
I may add the simple definition, coming from the prefix "tri" (lat. for three), there are three partners involved: two solid surfaces and a (separating) fluid in between those two. Tribologic is the science of friction, wear and greasing of friction partners in many kind like understanding the mechanism, forecasting and measuring wear rates and development of greasing fluids and pastes as well as protection layers.

It's a very complex science, especially on its application of a combustion engine. The complexity comes from the fact that it needs overlapping know how of kinematic, material, fluid mechanic, chemistry, thermodynamic. So you need an thermal and fluid engineer, chemist, material engineer and an mechanical engineer. It's very rare to have all in one person and it's even more rare to find one company altogether for the combustion engine. I was nine year in a ICE (internal combustion engine) development of the oldest company of the world producing ICE series for multiple applications: military, rail, marine, industry and commercial vehicles. The Leopard 2 engine is maybe the best known of them in the US. Even there you won't find someone who can combine all these areas as needed. It's always a share of everything in different deep dive qualities. I was one of them who were involved in failure related analyze, but there were specialists for different systems: valvetrain, crank drive and bearing and so on. None of them known everything and especially not the oil companies.

Pitting alone is complex, as the root causes are manifold and need deep dive know how down to chemical reaction basis background. So without any material investigation, e.g. SEM (scanning electrone analysis) where you can analyse the microscopic landscape and EDX (energy disperse X-Ray spectroscopy) the missing or added material content of a pitting structure, it is difficult to see it clearer. So my assumptions above are assumptions and no more.
 

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Arouse the DAMPFHAMMER!
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No, i didnt inspect roller bearings or anything else, i was just quickly checking timing chain stretch.
Should be on your list. The pitting comes with additional vibrations which can lead to seizure on the cam bearings.

Well chain was stretched quite much, but there is no error codes yet, wich is suprising...
How much was it elongated?

Yes, previous owner have been driving with realy low oil, and last oil change was like 50 000km ago o_O
Did you see oil pressure warning at the MIL? If it was low enough to interrupt the oil flow, it would be too late for more components then only the cams. In that case journal and main bearings at #4 would my next step to check it out.

Seems to be he thought of a looooooong range oil 🤨? Anyway once oil has very low corrosion inhibitors because of oxidation and wear of oil components may run the mechanism enough intensive for pitting at highly stressed tribological surfaces.
 

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Arouse the DAMPFHAMMER!
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"Red alert" oil light never seen, wich is good thing, so im pretty sure there has been just enought oil to keep engine barely OK :)
Oil pressure switch sensor alarms at veeeeeeeeeery low 0.5 bar, where oil flow suffers much. Normally bearings would be blamed long time before if oil flux would interrupt frequently. If the engine still runs at idle at same fuel flow and ign. timing, which is pretty sensitive, it would indicate the friction is not increased by non-proper working tribologic.

...so lets see if we can still revive this one to new life
You like playing game 😜. Good luck with your approach.
 

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Arouse the DAMPFHAMMER!
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@LotusElise could this play a part into changing the frequency of the LMAs making them vary in stiffness??
No, the exhaust side of the K20A4 has no lost motion springs as it has no different cam lobes which would be VTEC switched. It has only one cam lobe on the exhaust side. It's a compromise for lower cost as the benefit of having a secondary lobe on the exhaust cam is not of the value in that engine application, which is emission and low load efficiency.

The ECO concept for the K-series only sees a swirl induced low engine speed improve combustion efficiency. For emission certification cycle this is a miracle, for the daily driving it is quite limited, as VTEC switches already at 2500 rpm for the A4, means if the user don't drive high loaded low speeded, it is not fully utilized and we just speak about a potent 2-Liter engine. We still speak about a competitive power and efficiency level in the 2-Liter non-sport-sedan area. Only e.g. Toyota's Yamaha heads (2ZZ-GE, 107 hp/Liter) and the K-series internal competitor heads of the A2/A (Perf.)/Z1/Z3/Z4 (100-113 hp/Liter) are well better powered.
 

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Arouse the DAMPFHAMMER!
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For anyone having same problem, i did order this item from Ebay, with OE Number: 14120-PPA-010
I have now installed that Ebay camshaft. It was right one, and working well !
You mean those you have mentioned above? I would appreciate if you report later how it runs and if the cams are still good after the first 500 km :). That would be really great.

Thanks for the edit of the first post. Having all information in there makes it easy for time hunting members ;).
 
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