Redline
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What exactly happens at "redline" that is so bad on a car? I've always wondered this. Why is it that some engines redline at 5500 and some at 8000 and motorcycles even higher. What makes that one point and after so bad on the engine versus lower rpms? I have a feeilng its something to do with objects not being able to spin fast enough but want the actual info.
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Redline is the point to which the engine manufacturer has determined is the safe point for the engine to rev to. Some engines are designed to rev well into the 9000 RPM range (or higher). Engines such as those have been balanced to ensure that they will still operate properly at those points. Most auto manufacturers set the rev limit slightly lower than what the engine is theoretically safe to run at, the reasoning for this is because they want to build in a layer of safety and reliability.
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tjamz wrote:
Redline is the point to which the engine manufacturer has determined is the safe point for the engine to rev to. Some engines are designed to rev well into the 9000 RPM range (or higher). Engines such as those have been balanced to ensure that they will still operate properly at those points. Most auto manufacturers set the rev limit slightly lower than what the engine is theoretically safe to run at, the reasoning for this is because they want to build in a layer of safety and reliability.This is all true too...but the redline is more of a safety issue and reliabilty issue with the cylinder head and valve train. Dependate upon the system characteristics, the higher rpm's you go, the greater chance of valve float and the valve hitting the piston or busting the valve springs. Higher strength valve springs is the key to having a higher rpm. Next comes the engine being well balanced. Third is the lubrication system. If you really want a higher rpm, look into the valve train, it is the cheapest way to make sure you can run that high. But dont just go and see if you can go up there and replace parts. You need to see if there is a govener or limiter of some sort on the vehicle thatll hender it useless in those speeds.
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alot of this is true. valvetrane is one of the key factors in determining redline, but when you start pushing high RPM's, you start running into other factors such as crankshaft harmonics, rod/stroke ratio, camshafts, valve sizes, head ports, intake manifold/runner design and also at some point, cast pistons become very bad. breaking ringlands and piston skirts and what not.
Just because you CAN rev higher, does not always mean you should. I mean you theoretically could spin a QR25DE to 8 grand, but power will actually drop off because of the way it was designed.
McAdam
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