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What advantage is there Ducati's haviing Desmodromic valves?

From what I've read, it's supposed to cure "valve float" at high RPM. Ok, but don't Ducati L-twins not rev as high as inline 4's? What is it about them that makes them better than, let's say current techology the like self-adjusting hydraulic valve lifters that you would find on a Porsche 911? Surely Ducati could come up with a valve system that doesnt need to be adjusted every 6k miles.

There are certain things that make my S2R1K a complete Ducati:the dry clutch music, the beautifull pompone exhaust note and the single sided swingarm. The same cannot be said for the 6000 mile service intervals though.
 

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heathen!

there's been volumes of discussion on this... :p

valve float was a much bigger deal when ducati acquired the technology from mercedes, way back when (read: i'm too lazy to search for exactly when this was).

in the here and now? brand identity. it makes the motor unique.
 

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Besides the valve float issue, desmodromic valvetrains also allow for a much steeper cam profile. Without getting into the engineering aspect, it is a good thing.

For the most part, it's one of the things that makes a Ducati a Ducati, like the L-Twin engine overall, the steel trellis frame, etc.
 

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mustang said:
As for the rev limit, check out what HD gets for their stock engines.
No longer a valid arguement, as the Revolution 1200(Harley VRSC V-Rod) engine rev's to 9000rpms.

Then take a look at the Buell redlines, which are right up there with the Duc.


Granted, back when the Desmo valve train was introduced in the Duc, V-Twin redlines weren't as high, but now-a-days, it's just a tradition to have Desmo valves.
 

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Boy, this is the thing that almost made me buy a KTM over my new S4RS. Every time I went into my local Ducati shop someone put their hand in my pocket and pulled out about $1,000 - which didn't include actually adjusting valves, just checking them. Way, way back when spring technology was poor, desmo's were a fix for high rpm valve control. Now, shim under bucket or whatever the gang of four uses is at least equal so far as valve control is concerned. We can now control valves to the point that piston speed and crank survival is the probably controlling factor.

Having said all this, what did I just buy? - a brand new S4RS. But my current dealer says he charges about half what my old dealer did. After warranty I'll do the work myself anyway.

My Bro-in-law has a new KTM Super Moto that is a VERY good motorcycle. White power suspension and radio Brembo's too, for about $4,000 less than I paid for my S4RS. But I’ll probably be able to leave him for dead at some point on the speedo. That KTM handles VERY well.
LA
 

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88BlueTSiQuest said:
Then take a look at the Buell redlines, which are right up there with the Duc.
Buell Redlines are way below a Ducati's. The XB12 makes peak power at 6000 RPM and comes to a halt soon afterwards. Still a fun bike and is geared pretty well to make use of the power it does make.
 

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the springs on most inline 4's have very high compression rating. which means when lifting the valve, the engine uses power that you would like to go to the pavement for that action. since a ducati has no springs to rob power, it makes more usable power than an engine with valve springs. while this would most certainly not be noticable by us common riders, professional racers need every horsepower than can squeeze out of a bike.
 

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I'm with ya brother...though you won't get a whole lot of support from most of the DMLers I'm afraid.

The first two cylinder production motorcycle that Ducati made, the 750 GT, had valve spring heads. I think it would have been a great idea for Ducati to float that balloon in the Sport Classic 1000 GT. I mentioned it to a Ducati rep at VMD last year and his response, "Ducati will never do that."

I will continue to be a loyal Ducati fan with or without desmos...at least they should step out a bit and give it a try.

Retro sells in these troubled times...what is more Ducati retro than a GT with valve spring heads? I mean they now have wet clutches in some models (Bevel drives had wet clutches) so why not try a desmo-less Ducati?

I think we will go to our graves wondering that.

Keep preachin' bro...I'll turn the pages.
 

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eettare said:
the springs on most inline 4's have very high compression rating. which means when lifting the valve, the engine uses power that you would like to go to the pavement for that action.  since a ducati has no springs to rob power, it makes more usable power than an engine with valve springs.  while this would most certainly not be noticable by us common riders, professional racers need every horsepower than can squeeze out of a bike.

There is the main technical reason in a nutshell.

Also, it keeps dealers in business through service. A lot of car dealerships now-a-days are hurting, because the cars require so little work, they don't make as much as they used to. That is why they come up with a lot of BS gimmicks to get you in, even if it is not listed in the owners manual (transmission flush, etc)

mitt
 

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eettare said:
when lifting the valve, the engine uses power that you would like to go to the pavement for that action. since a ducati has no springs to rob power, it makes more usable power than an engine with valve springs.
Springs do not use power they store power. Whatever power used to compress them, going up a cam ramp for example, is given back when going back down the cam. RPM limits, previously mentioned above, is mostly a factor of stroke induced piston speed, not valve springs. Any direct benefit? - none, well maybe bullshit factor. Would I give up my desmo? NEVER! Mark
 

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I think it's an outdated technology, and I think that Ducati should come up with something new. It's about time.
 

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superjohn said:
Buell Redlines are way below a Ducati's. The XB12 makes peak power at 6000 RPM and comes to a halt soon afterwards. Still a fun bike and is geared pretty well to make use of the power it does make.
I had heard rumours that they were getting higher redlines this year, but looks as though that isn't the case.

The 1200's build peak HP at 6800rpms, the 900's build peak HP at 7500rpms....
 

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88BlueTSiQuest said:
No longer a valid arguement, as the Revolution 1200(Harley VRSC V-Rod) engine rev's to 9000rpms.

Then take a look at the Buell redlines, which are right up there with the Duc.

Woo. 9000 rpms. Take a look at the RPM ceiling on the SBKs. Just a TAD higher than that.

And if I remember reading the article correctly, the Buell FX bike was making it's peak HP at 7000 rpms which was 500 rpms below their redline. And we won't even go into the fact that none of the Buells even completed the FX race at Daytona.

On the post topic, Desmodromic valves don't tend to 'bounce' on closure as valve spring valves tend to do in a high performance application.

But, hey. If it is such an outdated technology, I will continue to be outdated. The desmo valve MotoGP bikes had the highest terminal speeds in MotoGP for a few years now and the engine does tend to factor into that a little bit.

Ryan
 

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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
 

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metalman said:
 

Springs do not use power they store power. Whatever power used to compress them, going up a cam ramp for example,  is given back when going back down the cam. 
That isn't 100% true.  You have losses due to friction, spring hystoresis, and poor force transmission angle going back up the cam.

A simple test is to spin desmo valvetrain my hand, and try to spin traditional valvetrain by hand.

mitt
 
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