Quote:
Originally Posted by stephen wilson
The problem isn't about the load on the engine while idling. Engines don't run as efficiently or cleanly at idle, so it can lead to excessive combustion byproducts in the oil.
Shadrach, you answered your own question. The reason to limit RPM's while warming up is because all of the engine components haven't warmed up, so internal tolerances won't be correct. It's not just a question of having some oil flowing. As far as the 2500 RPM number ( I usually hear 3000 ), I think that's derived from experience and common sense. You can feel it, 4000 it getting to the area I would consider high RPM.
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I did not say there was no reason to limit RPM, What I said was that I have scene "0" scientific evidence to support the 2500RPM number. You're right, it's not just question of having oil flowing. It's a questing of having oil pressure within the specified parameters. Too low and parts don't get adequate lubrication - too high and seals get blown. The latter is likely a bigger concern. Cold, viscous, oil + High RPM = High pressure. High pressure + cold seals = the propensity for a leak.
As far as tolerance and interference issues under normal conditions, my experience is that it's muchado about nothing with water cooled engines. Where oil temp is an issue is how it relates oil pressure. Many people have tried to pass off many old wives tails as coming from "experience and common sense."
I don't care if someone limits their RPM to 2500RPM until all the gauges are in the middle, it certainly is not going to hurt anything...what's mildly annoying is the people throwing out a hard number like there is some sort of science behind it. There's not as far as I can see, but I'm open to learning... I do believe that Porsche (imperfect as they've been through 986/996/987 lines knows something about engines and would not set a limit at 4K unless there was a reason to. BMW is the same, Some of the M cars had computer controlled red-lines depending on temp, but nothing as ridiculous as 2500.