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Re: AMA Superbike rules will prove to be better over WSB.

Racing should reflect the bikes ridden on the street, but not EVERY bike ridden on the street. Bikes that are manufactured for street use have all sorts of purposes other than for going very fast----comfort, LOOKS, SOUND, storage, wind protection, passenger capability, etc.....should we say that race bikes should have saddlebags and big chrome headlights too? No? Well, guess what, the fastest streetbikes are all inline fours, because it's easiest to make big power out of them, especially in an economic sense. A stock GSXR1000 beats a stock 998 just as a factory race 1000 is now killing (when it's not handicapped to the hilt) the factory 998's.

Why do we need to handicap the best engine designs simply to make sure that we have diversity in exhaust notes?
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

Ok lets keep this simple. Piston weight is a RECIPROCATING mass. The Space Shuttle doesn't accellerate to orbital velocity, stop and re-accellerate to orbital velocity 11,000 times in one minute. If you increase the distance that a given weight is being cycled through but keep the time (rpm in this case) the same, you are INCREASING the accelleration of that weight. This means that a longer stroke, even with the same piston weight will result in higher piston accelleration at any given rpm. Modern materials technology has a limit, hence maximum allowable BMEP and Piston Speed. That is why F-1 and for the most part the rest of modern high performance motors are trending to more "oversquare" (greater bore, shorter stroke) designs to allow higher rpms at the expense of some torque.

Still think my logic is flawed?
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

Holy crap KPaul you must be some kind of idiot to completely ignore the "all other things being equal" part. That rules out your whole deviant discussion of differing materials.
 

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Cute.



Our Imperial Personage sentences you to death by "reading debate between Longride and KPaul, with Lemon Juice put on the cuts" for the crime of being snide. :p



So let it be written; so let it be done.
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

That is all very interesting use of techno buzz words back up with no actual physics and your logic is still flawed. You are slyly coming around to my point by saying "Modern materials technology has a limit" but the rest is novice psuedo techno babble. To remind of your high school physics class acceleration is change in velocity period. Shuttle goes from 0 to very fast . Velocity is both speed and direction and acceleration is the change in velocity (any change). Force is the product of mass time acceleration. Thus the forces on the Shuttle are great pal. Yes a piston goes up (accelerates-then decelerates) stops then goes down (acclerates and decelerates) NOTHING SAYS MASS IS THE LIMITING FACTOR. OR STROKE (the length the mass travels) on speed. By increasing the stroke you increased the engine displacement thus the more gas explodes more force more acceleration etc. To save face you say "Modern materials technology has a limit, hence maximum allowable BMEP and Piston Speed. That is why F-1 and for the most part the rest of modern high performance motors are trending to more "oversquare" (greater bore, shorter stroke" Whatever pal so I am right its a material issue not a law of physics. Hey I am "only" an electrical engineer go ask a mechanical engineer. Given ideal materials a V-TWIN should be able to rev as fast a inline 4. I suspect valves may have more to do with why real world twins can't . But leave pistons, bores and strokes out of it. Oversquare has to do with the quality of the torque or more percisely the shape of the torque curve not rather there is a limit to rpm.
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

KPaul, so you admit that in the REAL world, He and I were both correct, BUT You're also continuing to assert that what I said was in someway equivilant to saying the big Space Shuttle can go no faster than the small 172?

You say: "Leave pistons, bores and strokes out of it." Why would we leave them out of it, when discussing the limitations of a particular engine configuration under an XXXcc cap? STROKE is precisely the reason that revs are limited in a V-twin superbike. Not coulda, shoulda, woulda.... but IS the reason. Yes, it is due to the limitations present with modern materials. That limitation being the inability of the crank, journal, con-rod, piston, pin, etc., to handle any greater accelleration.

Saying "Given ideal materials" is a cop-out. When we have "ideal" materials available for engine building, we can continue this discourse. Until then, your physics book should remain closed, on you shelf, and you should start talking to people who actually design and build engines with todays state of the art metals.
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

You state: "Oversquare has to do with the quality of the torque or more precisely the shape of the torque curve not weather there is a limit to RPM"

Uh... take that man's cigar away. No sir KPaul, the term "Oversquare" is simply a word used to describe the ratio of Bore to Stroke in an engine which has a greater bore than stroke. The shape of the torque curve is indeed partially affected by the Bore / Stroke ratio, but that's not what the term "Oversquare" is referring to.
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

Now you are retreating. You guys said V-Twins are limited by some psuedo tech law that bigger pistons can't go up and down fast. PERIOD. "STROKE is precisely the reason that revs are limited in a V-twin " WHY? WHY? What is the Physics behind your babble????? Big deal the piston goes farther. That does not tell me why it limits revs? Good grief Sean what was your major again???? Given ideal materials it makes no difference. THERE IS NO SCALE IN PHYSICS. Same principles apply to BIG things and tiny things.
 

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Sean's big **** theory of cylinders i.e. big ****s go slow

You dip sh_t I That ratio has nothing to do with your " big **** cylinder limit of RPM theory" It is just a ratio I know what oversquare is big ***** deal. You still have no physics behind your argument only psuedo tech babbling. You read something by some Cycle World guy and think is the law. Well as a engineer I can't afford to do that. I have to challenge everday assumptions. You are really hung up on this Bore/Stoke ratio. Engine designers have been playing with that since Damiler.
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

KPaul, I suspect that you are deliberately being obtuse. WHY has been answered time and again.... It is simply because we can't make anything strong enough to withstand the punishment required for more than xxxxxrpm with x stroke and x reciprocating weight. I NEVER NEVER said that it was theoreticly impossible with "ideal" materials. Why the hell are you using true unobtanium in infinity to discuss real world engines?
 

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Being faster in a street racing situation involves skill for sure, but mostly it involves who is willing to place the biggest bet going around a blind corner.



I recently did a track day. I was faster than some, some were faster than me. There was no bull*****. It was a completely honest experience that I highly recommend!



 

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Re: Sean's big **** theory of cylinders i.e. big ****s go slow

LOL, you're truly lost here. We are dealing with REALITY not with THEORY. The only thing in this discussion that has to do with physics is the equation used to determine the peak forces acting on reciprocating parts.

Is this a correct statement: "Stresses will increase at a given rpm, if you increase stroke" ?

Is this a correct statement: "Stresses will increase at a given stroke, if you increase rpm" ?

Are you honestly claiming that in the REAL WORLD, we could take a REAL piston + con-rod + misc bearings & pins and reciprocate them through an XXmm stroke at any rpm we please?

Are you honestly claiming that in the REAL WORLD, a heavier assembly won't reach it's structural limits at a lower rpm than a lighter assembly made of the same materials, at the same stroke length?

Are you honestly claiming that in the REAL WORLD, the reciprocating parts of an engine aren't limited by their ability to withstand the forces generated by reciprocation?

KP, I'm NOT arguing theoretical stuff here, I'm honestly asking you if you think that today's superbike engines aren't limited to a certain rpm, by the ability of their reciprocating parts to withstand the accelleration generated by their stroke?
 

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Re: Sean's big **** theory of cylinders i.e. big ****s go slow

After re-reading this thread I think I've figured it out.

You have been arguing apples to our oranges. We are not talking about what is possible in a textbook, or what is possible with perfect materials, perfect desigh and a perfect environment. We are talking about what is currently REALLY limiting rpm in the longer stroke motors (or in motors with heavier reciprocating parts)

YOU are arguing about what "Should" be. Unfortunately, that has little bearing on this discussion or on current motorcycle race engine building.
 

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Re: I'm pretty sure that's funny!

No, I was thinking of the Big Red CB1000.

At least neither are 600s. Couldn't take the razzing KPaul would give me.
 

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Re: Hard times for KPaul

You can improve your 600's torque by getting what is called a "torque wrench". Weld it onto the end of your crankshaft and give it a kick every time you need that extra special boost.

Trust me.
 

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Re: Go back to school Sean. Intuition can only be used by sucessfully by women

KPaul, Sean has a point here. What he's basically saying is that the real limiting factor is piston speed. It's that speed and the requirement to stop and reverse it every half RPM that eventually ends up with a rod thrown through the engine block. As stroke increases so does piston speed, further limiting maximum RPM. Now a smaller bore piston is a little lighter but not enough to offset the increased speed of the longer stroke. As always, too much of a good thing is detrimental. The more oversquare you go, the less volumetric efficiency you have, the more piston weight you have and the wider an overall engine you have.
 

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Go see a Dr. (Phd)

Sorry Sean, I really lost my temper back there sorry. No disrespect but I should of learned long ago not to argue science with the untrained novices you and the guy who start ed this thread. After talking to my mechanical engineering buds across the hall they noted that there are large engine 4000cc fours (each cylinder is 1000ccc) capable of sustained 20,000 rpm. They agreed with me that stroke doesn't limit rpm it just a dimenson (measurement). You seem to preoccupied with reciprocating bodies like they are some how different then the rest of physics. To the untrained eye I guess it is but to the trained engineer it isn't. Keep in mind acceleration can be caused by any change in velocity (which has two components speed and direction) UCLA has a good physics department go see them
 

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Re: Go see a Dr. (Phd)

Funny, my uncle is a mechanical engineer and he told me (talked to him yesterday) that increasing stroke will lower redline IF the weakest link happens to be the connecting rod/piston assembly. For the longest time valve gear was what determined an engines redline but lately, in most modern engines, it's the connecting rods that fail first. Now F1 and maybe MotoGP have hit their ceilings because of valve gear again so con rods aren't as much of a worry yet. But I believe superbikes and most definitley streetbikes aren't getting valve float/vibration issues. The weakest link is the connecting rod so increasing stroke will put more stress on it, therefore lowering the engine's redline.
 
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