Break in?

[bootlegger]

I know what a piston ring is, but thanks for linking that. And you are still not understanding what I'm saying. I never said high engine load at low rpm, i.e. lugging the engine, is not doing damage. I'm just telling you that high engine load at lower rpm will not be playing a major role in wearing down the imperfections on cylinder walls. Just stop and think for a bit, if you have a piece of sand paper, and you're using all your strength pushing it against a block of wood, it will NOT scratch the surface and smooth it out, you will only be able to smooth out the surface while you are rubbing the sand paper against the wood surface, and the faster you rub the sand paper, the faster it smooth out the surface. But at the same, the faster you go, the hotter it gets, that's how the first humans got fire (by rubbing two pieces of wood again each other). It's the same principle here with the engine, the faster the pistons move, the more wear is done to the cylinder walls, and more heat is generated due to friction, and tiny imperfections on a mostly smooth surface will generate hot spots and this will cause the material to heat up unevenly, which is bad.

I wasn't linking to a piston ring description. This is the specific part you missed: "Piston rings are subject to wear as they move up and down the cylinder bore due to their own inherent load and due to the gas load acting on the ring."
Loading the engine increases cylinder pressure, which loads the rings, causing wear as they move in the cylinder. Your sanding analogy doesn't work here, as the internals of an engine are always moving during combustion.
High load at low rpm is the most detrimental thing to an engine. Your lubrication is at a minimum at lower speed. High load at high rpm would be just as bad, but the engine receives the most lubrication at this point. Sure, ideally low load at low rpms is the best case, but most people live in a place where they have to push it up hills (like every time I pass on a Charleston bridge). This is the danger in making a specific suggestion like "keep it under 4k rpms". Not everyone is smart enough to know they need to keep the loads low. If you pass someone going up a hill in 5th (~2500-3000 rpm) vs 4th (~4500-5000 rpm), you are loading the engine more and causing more wear. Aside from that, the propensity for detonation is higher, especially with turbo engines, at low rpm high load situations.

Coming from the engine development world, we run-in a green engine for testing using very low load cycles. We run low to high rpms often, without straining the engine. Consider this like light passes with your sandpaper, but doing it thousands of times. It allows even break-in of the rings and bearings, which are really the biggest concern for a modern engine. Obviously this can't be done in a vehicle, so the legal speak in the manual has to make vague suggestions that basically say to take it easy. The vagueness is what frustrates us engineers. Shifting early means something different to everyone. Some idiot may think it means upshift often, despite load. This is why I tell people the 4k rpm thing is bunk. Run your car smart. Warm the engine before putting any load on, no racing, no high loads at low engines speeds, and don't frequently bounce off the limiter. You wont have any issues if you focus on those 4 things.

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[BmacIL]

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[DukeGaGa]

I wasn't linking to a piston ring description. This is the specific part you missed: "Piston rings are subject to wear as they move up and down the cylinder bore due to their own inherent load and due to the gas load acting on the ring."
Loading the engine increases cylinder pressure, which loads the rings, causing wear as they move in the cylinder. Your sanding analogy doesn't work here, as the internals of an engine are always moving during combustion.
High load at low rpm is the most detrimental thing to an engine. Your lubrication is at a minimum at lower speed. High load at high rpm would be just as bad, but the engine receives the most lubrication at this point. Sure, ideally low load at low rpms is the best case, but most people live in a place where they have to push it up hills (like every time I pass on a Charleston bridge). This is the danger in making a specific suggestion like "keep it under 4k rpms". Not everyone is smart enough to know they need to keep the loads low. If you pass someone going up a hill in 5th (~2500-3000 rpm) vs 4th (~4500-5000 rpm), you are loading the engine more and causing more wear. Aside from that, the propensity for detonation is higher, especially with turbo engines, at low rpm high load situations.

Coming from the engine development world, we run-in a green engine for testing using very low load cycles. We run low to high rpms often, without straining the engine. Consider this like light passes with your sandpaper, but doing it thousands of times. It allows even break-in of the rings and bearings, which are really the biggest concern for a modern engine. Obviously this can't be done in a vehicle, so the legal speak in the manual has to make vague suggestions that basically say to take it easy. The vagueness is what frustrates us engineers. Shifting early means something different to everyone. Some idiot may think it means upshift often, despite load. This is why I tell people the 4k rpm thing is bunk. Run your car smart. Warm the engine before putting any load on, no racing, no high loads at low engines speeds, and don't frequently bounce off the limiter. You wont have any issues if you focus on those 4 things.

And you missed the more important thing, moving up and down. If it doesn’t move, there’s no wear, physics doesn’t change. And no one said 4K is the limit, that is just a comparison to going to redline. And again, no one is saying to lug the engine, so could you just stop bringing that up? What we are saying here is BE GENTLE, lugging the engine doesn’t count as being gentle.:doh:

But anyways, keep doing what you do if you believe them. If you’re from the engine development world then you might know what you’re talking about, but I’m a engineer myself, and also have deep knowledge of how physics works, so I will keep doing what i think is right.

P.S. my sand paper analogy is only for the part where I’m talking about smoothing out imperfections, and I said engine load will play a role in wearing down other components, which includes the strength and rigidity of them. Also speed is more important than the total number of times in generating heat, so if you can’t recognize that, then we might have learnt physics in completely different worlds. And one other thing you're forgetting here is your factory testing is just a burst, not over hundreds of miles, it doesn't have enough time to do all the damage. What's discussed here is to not keep doing that all the time in the first however many miles the manufacturer recommends, for short bursts that's fine.

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