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mitt said:
That isn't 100% true. You have losses due to friction, spring hystoresis, and poor force transmission angle going back up the cam.
mitt
A simple test is to spin desmo valvetrain my hand, and try to spin traditional valvetrain by hand.

mitt

Come on Mitt, anyone can split hairs here... I'm trying to keep it simple by leaving the relatively minor (but not totally insignificant) forces of friction out of it.

RPM is and will always be limited by the length of your stroke, long stroke = fast piston speed, short stroke =slower piston speed. Too fast a piston speed and you get ring flutter from big heavy rings (that are on big pistons.... that are on twins).
Uncontrolled bouncing up and down of the rings between ring lands (flutter) leads to ring fracture which leads to bigger fractures!

monsterone6 said:
Less moving parts= More power , Simplicity= Better performance

I cant remember the link there was a test between the Buell XB900 and the S2R 1K. If you look at the dyno chart you can clearly see were the Duc starts making power around 4500-500RPM due to the Desmo system
Power not due to desmo, this is all cam lift, cam timing and duration, volumetric efficiency, compression ratio ... so many things working in concert. Confused about one thing tho, who has less moving parts here? Have you looked inside a desmo lately not to mention a 4 valve head on a desmo? Mark
 

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kJackd said:
and as a testament to this more effective ( I think) valve system, notice that ducs top the boards in every current race series ( except AMA...). Not the sole reason for current dominance, but but the big four are scratching their heads.
Which series would those be? I seem to remember a certain afro'd guy on a yellow bike cleaning up in MotoGP for the past few years.
 

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TimS said:
Which series would those be? I seem to remember a certain afro'd guy on a yellow bike cleaning up in MotoGP for the past few years.
BSB, WSB and MOTOGP are all being led by Ducati riders. But if you want to talk about the past, Ducati has more race wins than ALL manufacturers combined in all levels that they participate in as a whole.
 

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eettare said:
BSB, WSB and MOTOGP are all being led by Ducati riders. But if you want to talk about the past, Ducati has more race wins than ALL manufacturers combined in all levels that they participate in as a whole.
Well, this thread is sorta about history... and how perhaps these valves should be history, at least on a bike like the Monster. Anyway, talking about today, Ducati is not leading the manufacturer's points in MotoGP. They're tied for the lead in the driver's championship, and are 32 points behind in the manufacturer's championship.

Anyhow, I don't mean to demean Ducati (obviously I dig 'em, why else would I be a member?), but they're hardly cleaning up on the world stage as you make it sound.
 

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TimS said:
at least on a bike like the Monster
I could make a pretty strong argument that the Monster should be the very last model to lose the desmo.
TimS said:
they're hardly cleaning up on the world stage as you make it sound.
Actually the consensus seems to be that Ducati has the fastest bike this year. Bringing up #46 is like saying that Nike must make the best golf driver since Tiger Woods wins a lot.
 

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One significant benefit of the desmo system is it allows straighter intake and exhaust ports in a head of the same overall height as a bucket & spring style, or equivalent ports in a head that's shorter.
 

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Keep in mind, when argueing Ducati's past racing success, that twins have always had a weight and/or CC advantage until the last 2 years in sbk. They are also the only full factory team in wsb.
 

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mitt said:
A simple test is to spin desmo valvetrain my hand, and try to spin traditional valvetrain by hand.
That only tells half the story - sure its much more difficult to turn a traditional sprung valvetrain, but only half of the time - the energy required to compress the springs is largely[1] given back when they decompress - if you balance a regular cam at the right spot, a slight nudge will spin it until the next cam starts ramping up a spring. The "static state" comparison between turning a desmo valved cam and a regular sprung valve cam isn't what actually goes on when a motor is running.

big

[1] yeah, there are secondary losses due to heating the springs etc etc, but I'm guessing they're probably on the same order of magnitude as the losses in a desmo system accelerating and decellerating the pairs of rocker arms and the increase in friction due to two cam followers...
 

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🧟‍♂️🧟🧟‍♀️Zombies !
 
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