Quote:
Originally Posted by Irace86.2.0
Here are some points that cover my thoughts:
https://www.google.com/amp/s/amp.red..._of_an_engine/
Essentially the limits to revving seem to be with handling the heat/friction from the increased speed, handling the forces on parts like the pistons from the increased speed and finally handling the air flow required to not bottleneck the process.
My thoughts are that the forces are too temporary and the heat isn't able to build enough to matter.
The example that comes to mind that is relatable is how the foot experiences two to three times a person's bodyweight when it strikes the ground during running. So a 150lb person experiences 300-450lbs on one foot. Most people would buckle their ankle under that constant load if it wasn't for a half second like it is with a foot strike. Moral of the story is that peak forces may not matter as much as sustained forces. And there just isn't enough time in my opinion for enough heat to build to effect spring recoil or to cause bearing surface breakdown/thinning.
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Ok so take your person running and slam their foot into the ground just once at 2,000 pounds force and you are describing a gross over rev more accurately.
It has nothing to do with heat build up and everything to do with valves, cylinders and other moving parts. They are designed to move at a certain maximum speed and if you exceed that by to much even briefly things start to hit each other. This is what causes damage in an extreme over rev.
Again, you are not going to cause any damage at a coupe of hundred over since redline is a design spec not an absolute.