insbesondere @Ulf: Vorschlag fuer einen Fachartikel | Posts 16+

diesel.gustav wrote:

This means: when the system is in a warm operating state (only then do the operating conditions correspond to the design), very early on, short full-load cycles are performed, first at lower speeds, and then also at high speeds. . . . . In between, there are again phases with low load and medium to high speed. . . .. A slightly sporty driving style, combined with short bursts of full throttle (e.g., during acceleration), along with periods of partial load and, if possible, a little idling, as is easily possible in city traffic, significantly accelerates the break-in process and is good for the engine. Actually, I wanted to keep it short, as Ulf requested, and whether I have explained things clearly, you will have to judge. In any case, I am happy to be available for further discussion, but not until Wednesday evening at the earliest.

Hello Gustav.

Sure, thanks in advance.
In my opinion, this is already a practical and understandable guideline.

I have one more question for Wednesday evening.

Is the concept of the maximum piston ring travel (due to elastic deformations of the crankshaft and connecting rod at high speeds) practically irrelevant in real-world scenarios, given the differences observed at medium speeds?
or does it play a role that you account for through the

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phases with low load and medium to high speed

?

Deleted upon request.

Hello everyone!

@ulf, jan:

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The higher RPMs are intended to extend the break-in period of the piston rings against the cylinder walls to the greatest possible length (as Jan already mentioned).

The elasticity of the components of the crankshaft mechanism is likely to be in the range of hundredths or, at most, tenths of a millimeter at maximum speed (although I doubt it's that much).
Furthermore, the piston speed is practically zero near the top dead center, so the relative movement is not significant. Therefore, one cannot really speak of a running-in process in the reversal zones of the piston.

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The contact pressure is generated there by the piston rings themselves.

That's correct, although the radial clamping force of the piston rings is largely determined by the cylinder pressure. A piston ring is designed in such a way that the gas pressure behind the ring (on the inner side) can seep through to generate the clamping force necessary for sealing. At the same time, the pressure force pushes the ring axially against the side of the piston ring groove that is opposite the combustion chamber, thus providing axial sealing.
The conclusion is that the engine needs to be loaded somewhat to achieve an effective break-in process for the cylinder walls. But of course, in moderation!!!

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Hm, are these also piston pumps (i.e., essentially built like a 4-stroke engine), or are they other designs?

This includes piston pumps, specifically axial piston pumps and radial piston pumps. A very special example is found in every TDI engine: the diesel injection pump!
However, our units are calibrated for significantly higher performance and low pulsation.
The nominal pressure range for axial piston pumps is typically between 280 and 350 bar, with some models reaching up to 500 bar for specific applications.
Radial piston pumps are typically used for specialized applications requiring exceptionally high pressures, which are usually around 700 bar.
If you have a more specific technical interest, feel free to send me a private message. I think going into more detail would be off-topic for this forum.

Regarding the break-in process: I believe that frequently changing load cycles are important, both to achieve the necessary pressure on the components and, on the other hand, to create a certain "pumping effect" (breathing of the gap) that promotes the removal of wear debris.

Regards,
Alex.

Deleted upon request.

diesel.gustav wrote:

Alex has already written about why the RPM is not so important.

Hello Gustav.

Okay, so we already have 2 matching and expertly informed opinions.

At the time, I adopted my father's viewpoint, which, although based on a certain level of technical knowledge, was not the result of formal education, and I considered it to be "logically sound."

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I would like to add a little more, as announced yesterday: High RPMs at low load do not cause the engine to "overshoot." Utilizing the maximum piston travel in the +/- TDC (top dead center) or BDC (bottom dead center) (is that what your approach is aiming for?) can only be achieved under near-full or full load conditions through deformation of the crankshaft, main bearings, connecting rod bearings, connecting rod, connecting rod bushing, piston pin, and piston. This is already integrated into our break-in program, which includes full load operation. ...

Hmja, in the UT, high gas forces and mass forces naturally act in the same direction and try to push the piston as far as possible into the crankshaft mechanism, but in the OT, high full-load gas forces counteract the mass forces of the piston, connecting rod, and crankshaft journal.
Therefore, the maximum piston stroke in the top dead center (TDC) range, between the compression and power stroke, can only be achieved at high engine speeds and low load. (For example, by playing with the gas while idling, in a somewhat "half-hearted" manner ).
Between the exhaust and intake strokes (i.e., every other revolution), the engine speed is the primary factor, and the load is less relevant.

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@ all: In another forum, there were over 1600 readers discussing the same topic. What are your thoughts on that?

That's quite remarkable - unless every "junk" thread has 10,000 readers .