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What good are desmodromic valves if you don't use the rpm? The Duc must be strangled.



The Honda is supposed to make max power at 12,500 rpm; here it's happening at 13,200. Allowing overrev to 15,000 makes more sense.



What's wrong with the Suzuki? It was much better last year.



I wonder how good these numbers are.
 

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Thanks VWW



This seems like a more useful report than the one the other day with aftermarket pipes. Doesn't really matter what the absolute numbers mean -- that is, how they equate with SAE horsepower etc -- what matters is how they compare to each other.



Really illustrates the fundamental difference between a twin and a 4. If you want torque and ride below 10000rpm, the Duc is impressive. If you wind the snot out of them, the 4s kick ass.



Cheers

Bob
 

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I'm not sure if you noticed, but 11,000 rpm is pretty damn high revving for a 750 twin. An SV650 redlines at 10,500, and it's a smaller engine. The limitation they're running into is (I think) piston speed, not valve float. One of the engineer types can comment on this in more detail, but a piston can only move up and down so fast before it somes apart
 

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Now THIS dyno actually means something, unlike that Aussie dyno a few days ago. For the most part, it looks exactly like I expected.



The Kawi's steep jump in Torque and HP is at 7,500 RPM (others are later), but otherwise it's smoother than the rest. Yummy
 

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That is more like what I expected.... I can't believe that the GSXR has fallen that far down in HP compared to the new bikes. Everyone was trying to compare the ZX6R dyno to the numbers from last years GSXR dyno.... You can't do that. This is a valid test. All bikes on the same dyno on the same day. Now you can make comparisons. I think Kawi has the right idea with the extra 36cc for the road bike, but I am very impressed by the Yamaha's graph! I just wish I could have the 636 motor in my 2001 6R.... I sat on the new one and it is a very comitted riding position. I'll be keeping my 2001 though... much better for 300+ mile days IMHO.
 

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>>What good are desmodromic valves if you don't use the rpm? The Duc must be strangled<<



I would like to see someone develop a 4 with desmo valves (maybe Ducati will, to capitalize on the hoped for success of their MotoGP V4) that could make maximum advantage of the desmo characteristics.



However, there is still a benefit at somewhat lower revs. Cams for desmo valves (as well as pnumatic valves) do not require the gentle opening and closing ramps that spring-closed valves require at even modest rpm. In turn, this means that they do not need the excessive valve overlap required for most high performance applications. This is part of the reason for Ducati's strong midrange.



As the good captain whoopass points out below, rpm limits for the Ducati are more a function of piston speeds than valve train. Another limitation is that the large bore results in a long flame front in the combustion chamber, which becomes problematic at higher speeds (which is exaggerated if they were to go with an extremely short stroke/bigger bore to deal with the piston speed limitation.



This is the theoretical jsutification for the 250cc advantage that WSB and AMA Superbikes used to give for twins (and the 100cc for triples). Based on then state of the art piston speed limits and bore/stroke ratio limits, this gave approximately equal potential HP. Technological advances have raised the bar on both, which is how the displacement advantage has seemed unfair recently.



Kevin Cameron had an article on this in Cycle World a few months back that explains it much better than I can.



Cheers

Bob
 

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I had many friends and family ride my TL1000 and ZX9R over the last couple years. They are all average to above-average street riders. To a man, they all thought the TL1000 was the faster bike on the street. Since most street riding doesn't include a trip to 11,000 rpms, the TL FELT faster at the speeds MOST people ride. Between 4 and 8 grand the TL pulled like a train and then leveled off, and the ZX starts slower and then pulls like a much faster train from 8 to 11. I certainly like them both, but the midrange torque from a nice twin is very nice for the everyday rush. Throttle snapping the frint wheel up from 4 grand is much fun. Bad news for Joe Squidly, who can't brag about numbers or beat his buddies bike over 130 mph. He doesn't know what he's missing.
 

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Can someone help educate me on why a Ducati 750 is compared to Japanese 600s (Aside from the fact that Ducati doesn't make a racing 600)? Shouldn't a 750 blow away a 600? If Ducati made a 600s, would it get totally destroyed by the competition?
 

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When is the Honda going to lose some weight and gain some HP. They claim "Performance First" but always make the least HP and weigh more.



Hay HONDA are you listening, YOU ARE 3 YEARS BEHIND!!!



The undertail exhaust is coooool, but the Yamaha still looks better.



I am going to do something this year I have never done before. I am going to buy something other than a Honda.
 

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Desmo valves

As rsheidler pointed out, the desmo valve train has advantages at low RPM. In real world terms, the desmo valves give the ability to have absolute control over valve timing by eliminating the inherent lag of springs. Compression can be held to the last possible moment, allowing for greater torque production, etc. You can hear it in the exhaust note and see it on the torque curve.

Vlad
 

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Re: Desmo valves

Vlad, besides the more obvious reasons that the 750 desmo twin is making more power a low RPMs, one factor is that there is very little hp loss from compressing the stout valve springs needed to control the valves in the non desmo high RPM fours. Granted there is some frictional loss from the desmo's complex valve train, but it is more than compensated for by the lack of stiff valve springs. VWW
 

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My God, there is still somebody out there that hasn't understood the whole 1 cylinder, 2 cylinder, 3 cylinder, 4 cylinder, 5 cylinder, 4-stroke vs 2-stroke limitations?



A twin isn't going to make as much horsepower as a four, and it all has to do with the physics of air flow, more combustions, etc. By your question why don't you ask "shouldn't a DR650, KLR650, or XR650 blow away the measly 600?" How come 600s make more power than huge 1400 cc twins? Pure capacity does not translate into hp. Hence WSBK rules that gave weight breaks and capacity breaks to not only twins but triples too (I guess trying to get Triumph in). Hence the current MotoGP rules that give significant weight breaks to twins/triples, and penalizes 6 cylinders compared to fours/fives. Why do you think Honda went with the five? On the same side it takes a 1000cc four stroke to make as much power as a 500cc two-stroke. Why do you think motocross series allow double capacity four strokes in 125 and 250cc series?



 
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