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

Even with restrictor plates that suzuki is all over hodgsons @ss... Who'd Ducati blow at WSB?
 

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Somewhat useless write-up

I don't think the test was needed. Seems like MO just is straining super hard to find things to chat about just to keep you other fellas on here from crying about your 11 dollars you spent.

Just kidding........
 

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Re: Any Chump Can......

Just as any chump can highside (or wash out the front due to driveline lash) a 600 while trying to keep up with the liter bikes out of corners on a public road.

The street is not the place to explore the limits of your bike.
 

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Re: Johnny.... you missed a great opportunity.

No. I am saying that AMA rules that weigh displacement very heavily, while ignoring other equally salient features like valvetrain configuration, number of cylinders, type of cooling, or type of combustion cycle (two stroke versus four stroke) are at best patently stupid, and at worst a result of graft.

A four stroke should get about twice the displacement as a two stroke, no problem, the math works. Along those same lines, I don't think it would be unreasonable to see a bored out 1200 cc Buell XB9s (air cooled pushrod 45 degree V Twin) racing against 600cc water cooled overhead cam inline fours. I think the math supports it, or something close to it. And maybe a SV-650 (water cooled oversquare OHC 60 degree twin) at closer to 850cc's.

These bikes (600's, SV-650, XB9) are about being quick, light, and maneuverable, not about breaking the sound barrier while handling like a truck. Think of them being classified by the kind of track where they thrive.

People hung up on power versus displacement as their only (or primary) metric for "quality" are only showing their ignorance of physics (IMHO).
 

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

"The 250cc advantage of VTwins" is not some sort of arbitrary "we love VTwins" bonus rule, it is the result of simple physics. Four smaller pistons will *always* be able to make more power then two larger pistions. The math is simple and well known. Just like a two stroke will always make nearly twice the power of a four stroke. It's simple physics.

Ducatti may have been dominating the races with their VTwin, but it was not the extra 250cc's of displacement, it was optimized piston geometry (very oversquare) and the desmo valvetrain. Add that same desmo valvtrain to an inline four, watch it get less valve float at higher redlines, and watch it walk away from a non-desmo 4. If you don't believe me, check the lap times of the new desmo V fours. Ducatti was winning because it had a more sophisticated valve train.

If the AMA wanted to make a displacement adjustment for the physics advantages gained by a desmo valvetrain, I have no beef. But they effectively nuked every V-Twin.

The RC51 was doing well because honda dumped buckets of money into it. And watch it get eaten alive by the new Honda V5's of equal or less displacement.

You are right, nobody makes two strokes for the (U.S.) mass market, they suck as street bikes. Power is peaky, maintenance is high, pollution is bad. So you are saying that the race bikes should mirror what makes a good streetbike, right? Then we agree! The bikes that race in these types of classes should reflect the bikes that are being ridden on the street.

But then you seem to be asserting that the only valid sport oriented streetbike engine configuration is a watercooled overhead cam inline four!?!? That is just plain stupid. For the streetbike type classes we are talking about, the rules should be based on physics, and should exist to try and equalize all valid and reasonable commercial offerings.

As written, the rules effectively mandate a liquid cooled, four (or more) cylinder, desmo or overhead cam engine. Any other configuration is at a HUGE disadvantage.

And I reiterate. Claiming that the only measure of "quality" of a sportbike engine is simply power produced versus displacement simply demonstrates ignorance. I can think of a half dozen or so more significant metrics off the top of my head. That measure of "quality" would mean a two stroke would be the ultimate sportbike street engine, which is obviously false.

;) And if you want racing classes to be built around "most popular streetbikes", then how many pushrod twins got sold over the last few decades versus inline four OHC's ;)
 

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

:) Missed one :)

Tweaked but still *very* streetable Buell Firebolts (bumped up to 1200 cc's) are being built today by Nallin Racing in Colorado. Dyno's have been posted nosing right around 110 horses, with a torque curve that is to die for. With that setup they won't be dominating anything, but they could be competitive on some tracks, and would make for some entertaining races, and it would be nice to see at least one American Motorcycle racing in that American Motorcycle Associating Professional Racing series.

I don't know what people are doing to SV-650's, but I would be suprised if it were not possible to massage that into a competitive platform as well. That would be another great bike to see mixing it up.

Don't give it advantages the physics don't warrant, but dont pick some stupid rule like "displacement is the only valid metric" and base an entire "professional" series around that. Is the AMAPR that stupid? If that's the best they can do, what good are they?

Even the stock XB, which is way down on power, was going toe to toe with an F4i on tight and technical tracks. You know, the kind of tracks that the inline four 600's like to race on...
 

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Peak HP vs Torque (Ftlbs, Newton Meters) be clear what you are talking about

Actually you should clarify by power do you mean horsepower or torque. You assertion that multliple cyclinder makes more power is true if you are talking about peak horsepower. If you are talking about torque the 2 cylinder bikes have an advantage at low rpm levels. At higher rpm levels the advantage goes away (given the same displacement). As an engineer I think it wrong to make a blanket statement that " Four smaller pistons will *always* be able to make more power then two larger pistions. " Are you talking abut Peak HP or Torque (which arguably wins races at least that is what Ducati thinks) ????
 

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Who won last years WSB?

Colin Edwards with a Honda RC51 so much for Desmo valves. I think you overstated that point.
 

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Re:Correction

Four smaller pistons will *always* be able to make more power then two larger pistions.
You should add: "at the same displacement."

The rules were in place so that the amount of air that an engine can pump per unit time would be close to equal. 750cc Four vs. 1000cc Twin = about the same pumping speed given the differential between maximum piston speeds. As reepicheep sez, it's not favoritism, it's physics.

One other reason for the advantage of the twin is not only the midrange power availablity but also the traction advantage gained by the power pulses of a V-Twin over an I-4.

"The twins also put the power on the ground differently than a four. With most fours, one piston is usually on its power stroke at any given time, so a four will feel smoother but it will also spin the tire easier for that same reason. With a twin, one cylinder fires then the other so you have the effect of turning on the motor then turning it off. The tire will actually start to spin then be off of its power stroke so it will regain traction. This pulsing effect gives the twin an advantage in the traction department. In the Grand Prix two-stroke class a couple of manufacturers produced what was known as a "Big Bang" engine, where all of the cylinders would fire almost simultaneously to give this same traction advantage."

-http://www.boldbikes.com/techie/no99tech.html
 

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This is MO. There is no point.

Close, but you missed the real pointless goal: any reason to go to the track to flog race-like bikes. Can ya blame MO?

We're running out of (excuses?) track-bound reasons, though. {Sigh}
 

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Re: Peak HP vs Torque (Ftlbs, Newton Meters) be clear what you are talking about

Torque is not a measure of power, horsepower is a measure of power. Torque is force, the distance that force is moved through results in power. 50 foot pounds of torque at 5000 rpm is identical to 25 foot pounds of torque at 10000 rpm.

Torque by itself is meaningless. It is the torque times a given RPM that is meaningful. What is significant on a street bike (and is not generally well enough appreciated) is the shape of the curve of horsepower versus RPM. Why a twin typically feels so much better as a street bike, is because a twin will typically make more power sooner. Whatever RPM you are at, just whack the throttle and the bike leaps. On an 600 inline four, if you are below 4000 rpm or so and whack the throttle, you might as well be riding a vespa. You are lucky to be getting 25 horses down to the road.

Ducatti may say "torque wins races, not horsepower", but it ain't their engineers saying it. What they may mean to say is "a broad and flat power curve does better in races then a narrow peaky power curve given similiar peak power levels".

I stand by my assertion. I could clarify it by saying "all other things being equal, a two cylinder engine will never make as much power as a four cylinder engine", but I think the meaning was clear in the original context.

So you can increase torque by moving to a larger piston with a longer stroke, but that then limits your peak piston velocity significantly. If you do the math (I can't, but I can point you to some Kevin Cameron articles that can), you will find that in terms of peak power, you gain faster by increasing RPM at the cost of torque then you gain by increasing torque at the cost of RPM.

Don't get me wrong, I ride and love twins. But if twins were so magical for racing, why is Ducatti getting ready to crush their old twins with a new desmo V four? Why is Honda moving from dominant twins and fours to V fives? Why are formula 1 racers V12's and V16's (I think, not really into F1).

Here's some more blanket statements to bother you ;)

1) A system at rest will remain at rest until some outside force acts on it.

2) A closed system cannot produce more energy then it consumes.

3) Liquids are not compressible.

I agree blanket statements should be made carefully, what is most of math and physics is full of them.
 

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Where did you go to school?

Torque is not force, Force is a component of Torque. T=F x d T=Torque = Force x distance (Newton meters is the unit) check your units Freshman. Newton is the unit of measure for force. Newton meters is the units for Torque. Physics 101. A simple example of Torque is a lever. Think about it.

Also tell me why "by moving to a larger piston with a longer stroke, but that then limits your peak piston velocity significantly" instead of quoting from Cameron. He is fine for the layman but he leaves the details out a lot.

Your blanket statement don't bother me kid since I have a degree in Engineering. But they are unrelated, not well organized and don't mean much in this context. Get a degree in engineering and then come back and show me.

More to think about kid Force = mass x acceleration.

acceleration = dv/dt
 

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Re:Correction

Well with Ducati dumping the twin pulse idea on the new V4 where do you stand now? Granted Caparossi spun the hell out of that thing before he dumped it last week but there had to be a reason the twin pulse concept was axed.

Thinking about it, the pulse effect it seems more likely that the twin pulse would rip the tire up quicker than a 4 pulse motor of equal power. With a 4 pulse throttle control would be less violent as each power pulse would be half of what a twin would put out, though more often. So like you say you have a steady smooth power output instead of a less steady more violent twin pulse. Being that the twin pulse would roughly be twice as strong as a single pulse on a 4. Ether way it still comes down to throttle control.

You mentioned that some "produced" the big bang engine, did anyone stay with it?
 

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Re: Peak HP vs Torque (Ftlbs, Newton Meters) be clear what you are talking about

You got it wrong. Torque is what accelerates you. HP is just an equation of torque and RPM that helps you gear the vehicle properly to maximize the torque its engine produces. If you used a G-force monitoring device it will show more acceleration at 50 ft/lbs @ 5000 RPM than at 25 ft/lbs @ 10000 RPM (assuming, of course, we stay in the same gear.) The HP figure helps tell us how to gear the motorcycle and when, as a rider, we should upshift. Once you go past the peak HP, the advantage of the greater torque multiplication of your lower gear over the next higher one is gone, and it's time to click that shift lever.
 

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Re: Peak HP vs Torque (Ftlbs, Newton Meters) be clear what you are talking about

My above post was for reepicheep, not KPaulCook. He's right. ;)
 

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Re: Peak HP vs Torque (Ftlbs, Newton Meters) be clear what you are talking about

BTW, the real (basic) reason the current 1 liter 4's have an advantage over the 1 liter twins is revs. Revs, revs, revs. They can produce almost as much torque, but at much higher RPMS (which translates into higher peak HP, which is why it becomes such a key number.) Because of this the 4-bangers can gear their bikes shorter than the twins. That means they have more torque multiplication through the gears which tranlates to more torque at the rear wheel. When all is said and done, this is what counts for acceleration. Also, the higher your HP, the higher your top speed is going to be (all other factors like aerodynamics, etc., being equal of course.) There is a point, like all things in engineering, where you can have "too much of a good thing." More cylinders translates to more pumping losses and larger overall size with an engine. Ferrari's Formula 1 is a good example as that's what finally made them give up their very traditional V12 in favor of the current V10.
 

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Wheee! Look at me! I'm an Engineer!!!!!!

Sigh. Torque is a force. For meaningful discussion, a great way to normalize the conversation is to discuss torque as force at a given distance on a lever arm in rotation. When "normal" people talk about motorcycles and torque, the ones that aren't *ssholes generally understand it as meaning the force applied upon a virtul lever one foot long extending from the crank. (unless they are Europeans who are not *ssholes, which would use newtons and meters). The general discussion is typically relative to what you would see produced on a typical dyno chart.

We can grind down into the individual units if you must, but they have no bearing on my original point, which still stands. Torque (as produced at the crank) is totally irrelevant. It is Torque x RPM that is the meaningful measure, and it is called horsepower.

Torque is not a measure of power. Horsepower is a measure of power. I hoped it was clear from the context of the discussion that I was referring to "Torque" and "Horsepower" as the lines that appear on a dyno chart. In that regard, torque is meaningless unless you consider it relative to a given RPM. I would have thought that was clear when I summarized by saying "50 foot pounds at 5000 rpm is identical to 25 foot pounds at 10000 rpm"?

Are you still trying to assert that torque, independent of the RPM at which it is applied, is a meaningful measurement of motorcycle performance?

As to why moving a piston through a larger stroke limits your peak velocity... I would think that would be obvious to an engineer. Take a big hunk of metal. Just for fun, lets call it a "piston". Attach it to the end of a metal rod. Lets call that a "connecting rod". Now shake that rod up and down faster and faster until something breaks. Now take a smaller piece of metal, and connect it to a rod that is half as long, and wiggle it up and down through half the previous distance until something breaks.

Which chunk of metal was moving at a higher velocity when it broke? Remember, one up and down shake of the first test (lets call it "the twin") covered twice the distance of the second (lets call that one "the four"). Which chunk of metal experienced the greater acceleration forces? Which test had the greatest changes in inertia? Which experienced the highest velocity.

You can play with the diameter of a piston versus the distance it moves through to try and limit the maximum velocity seen by a twin (going to a pistion that is bigger around but moving through a shorter stroke), and this indeed does allow higher RPM's. But you can make your inline four pistion oversquare in the same way, and get them a further rpm advantage as well, resulting in no net gain for the twin. And as the piston gets bigger around, you start to have other problems that limit maximum performance, so the inline four is always ahead (sigh... all other things being equal if thats not obvious).

So stop obsfucating with derivations and units. What I wrote was obviously meant as an accessible and high level discussion of generally applicable truths using common venacular.. Had I wanted to produce a mathematical proof, I can assure you I would have structured it far differently.

Your original assertion seemed to be that the torque (measured at the crank of an engine) was more important then horsepower, and that an inline four has no built in physics advantage in power produced per CC of displacement then a twin. If this was the case, then defend these statements. If this is not the case, then I apologize for misunderstanding you and we don't disagree.
 

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I got your post. I think the other poster was a little angry though.



i think mr aero head is pretty damn funny. :)
 

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Re: Peak HP vs Torque (Ftlbs, Newton Meters) be clear what you are talking about

Oh good. That means in a drag race, my Buell Cyclone, which is producing 85 or so foot pounds of torque (at 6000 RPM), will totally humiliate the GSXR-1000 described in this article, which is "only" producing producing a maximum of 75 foot pounds of torque (at 11000 rpm).

And here I thought all this time the GSXR-1000 would kick my Buell's ass. I can hardly wait to hit the dragstrip. :/

But wait. I wonder why the dyno chart reads 140 horsepower for the GSXR-1000, but only reads about 87 horsepower for my Cyclone. Oh well, it must not be important, I GOT MORE TORQUE... WOO HOO. Gotta get out to the edgewater dragstrip and start humiliating those Gixxers...
 
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