How is an engine's redline or maximum speed determined?

Question

Without trial and error and thus destroying an engine (or several engines), how would one decide what the maximum safe rpm's of an engine would be? I can understand that the factory may be willing to sacrifice several engines in an experiment of selfdestruction but I do not believe that the redline on a factory tach is that accurate. I have seen cars with the same tach and same redline shown on it despite quite different engine options. I also believe that the factory would pick a conservative RPM and then show the redline to be somewhat below that, just to discourage people from abusing their product (especially while under warrany) So, if some hotrodder takes an engine and has it balanced, and new cam and springs installed and any number of other modifications, how does he know/guess what the redline will be ? That is without actually destroying the engine and then deciding that the redline would be less then that.?

Answer 1

Here is the rule of thumb. Figure out the piston speed in feet per minute. (stroke X max rpm you want to run,devided by 6) never go over 3500 feet per minute for stock engines, 4000 feet per minute for modified engines and 5000 feet per minute for all out race engines. example, a 4.25 stroke length stroker motor should not go over 5600 rpm for a modified engine.

Answer 2

Factory redline is almost always conservative, but usually the first thing to happen at a high RPM is valve float. The springs aren't strong enough to close the valves before it's time for them to open again so you get no compression. In a pushrod engine (most older/american V-6 and V-8 engines) There's more stuff moving so it's an even bigger problem. After that, it's usually piston rods or pistons.
when you double the engine speed, you quadruple the forces acting on the components. If I remember, things like detonation get more tricky at higher RPMs too, so you need better tuning.
ALL high revving engines have standalone engine management.
the factory NEVER pushes an engine to anywhere near it's full potential.
Most cars out of the factory do 6500 for a 4 cylinder, 6000 for a 6, 5500 for an 8(I think). Japanese cars tend to rev faster. Usually the factory rev limiter is set low as you assumed to save wear and tear. There are alot of technical foums, and alot of people pushing the limits of the engines, so basically not many people do something that hasn't been done before. Even when you do something kind of new, you still have a basis to work off of. No decent hotrodder EVER builds an engine without doing research.

Answer 3

Redline Engines

Answer 4

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Answer 5

An engines 'redline', is based on the feet per second, that it can withstand, over a given set of cycles. Your best bet, would be to go to an engineer, and have him calculate the stress analysis factors, that you've introduced, by modifying the whole lot. Regardless, nothing is forever. ( the term used for this, is non destructive testing)

Answer 6

this is a point the factory rates the engine at running in the danger zone,,i know we all think the red line id just a mark,,but it is actually the point the vehicle,will run at for a certain amount of time ,,without blowing up,,of course on now day cars the red line is actually controlled by the computer ,,when an engine reaches this point the computer will shut the ignition off for a fraction of a second ,,long enough for the engine RPM,s to drop,,,this is done as a safety feature,,to keep from blowing motors,,and also to help save lives,,i hope this helps.

Answer 7

If you modify a car for your whatever, then you must create your own spec's. Man you are dealing with a machine and the weakest link in the chain will fell every time. You have got to know your own creation and you are going to destroy it from some or do to some miss calculation, that the fun of it.

Good Luck

Answer 8

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Answer 9

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