Engineering question about overreving
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Engineering question about overreving
I recently overreved my GSR engine to about 11000rpms for a split second 
. It still runs and has perfect compression 
. The idle is rough though....something probably wrong with the valves 
Since the rods/crank are designed for long if not infinte life at 8000rpm, is it safe to say that no real damage/ life reduction has been done in taking the thing to 11000rpm where the stresses are almost twice as high? Doesn't designing for fatigue require everything to be like 10x stronger than any stress it will ever see?
Is my logic correct? Am I omitting any important variables, such as vibrations, lubrication, etc?
I just don't feel like replacing the whole thing....
. It still runs and has perfect compression . The idle is rough though....something probably wrong with the valves Since the rods/crank are designed for long if not infinte life at 8000rpm, is it safe to say that no real damage/ life reduction has been done in taking the thing to 11000rpm where the stresses are almost twice as high? Doesn't designing for fatigue require everything to be like 10x stronger than any stress it will ever see?
Is my logic correct? Am I omitting any important variables, such as vibrations, lubrication, etc?
I just don't feel like replacing the whole thing....
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Re: Engineering question about overreving (Lsos)
I don't think I'd "replace the whole thing" because the idles a little rough... you may have just loosened a motor mount or a sensor could've gone bad...
sure there could be damage but I don't think anything serious if it's not blown up...
Oh and the bottom end isn't really the concern with over-reving... it's the top end... the springs can't close the valves fast enough and they end up floating and potentially getting bent to hell.. (generally the piston survives the incident but NOT always by any stretch).
Modified by NonovUrbizniz at 3:36 AM 8/8/2003
sure there could be damage but I don't think anything serious if it's not blown up...
Oh and the bottom end isn't really the concern with over-reving... it's the top end... the springs can't close the valves fast enough and they end up floating and potentially getting bent to hell.. (generally the piston survives the incident but NOT always by any stretch).
Modified by NonovUrbizniz at 3:36 AM 8/8/2003
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From: San Jose, Ca, USA
Re: Engineering question about overreving (Lsos)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lsos »</TD></TR><TR><TD CLASS="quote">
Since the rods/crank are designed for long if not infinte life at 8000rpm, is it safe to say that no real damage/ life reduction has been done in taking the thing to 11000rpm where the stresses are almost twice as high? Doesn't designing for fatigue require everything to be like 10x stronger than any stress it will ever see?
</TD></TR></TABLE>
Designing for fatigue failure is usually with cyclic loading. Continuous loading at the same or near same conditions. Otherwise when designing something...there is always a safety factor associated it. Usually safety factors are around 2X not 10X. Thats why they set a redline of 8000 rpm because when you go past that mark...there is no predictions on what may happen to the engine.
The Rods/Crank have been designed to run "infinite life" (long time) under regular loading. Not a 8,000 rpm constantly. So keep that in mind.
Hope that helps.
Since the rods/crank are designed for long if not infinte life at 8000rpm, is it safe to say that no real damage/ life reduction has been done in taking the thing to 11000rpm where the stresses are almost twice as high? Doesn't designing for fatigue require everything to be like 10x stronger than any stress it will ever see?
</TD></TR></TABLE>
Designing for fatigue failure is usually with cyclic loading. Continuous loading at the same or near same conditions. Otherwise when designing something...there is always a safety factor associated it. Usually safety factors are around 2X not 10X. Thats why they set a redline of 8000 rpm because when you go past that mark...there is no predictions on what may happen to the engine.
The Rods/Crank have been designed to run "infinite life" (long time) under regular loading. Not a 8,000 rpm constantly. So keep that in mind.
Hope that helps.
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