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Topic: Ducati's Variable Valve Timing  (Read 7505 times)

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mugwump58
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« on: October 21, 2014, 12:00:02 pm »

Not a lot of technical data, but I'm procrastinating.

« Last Edit: October 21, 2014, 05:26:43 pm by mugwump58 » Logged

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« Reply #1 on: October 21, 2014, 03:42:56 pm »

VTEC solo calci yo!

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« Reply #2 on: October 22, 2014, 03:31:56 pm »

I was wondering about 2 issues with this design: 1) how the cam belts would effect changes in timing/cam phasing since they stretch over time, and 2) shim/valve clearance changes, as that might that cause some valve-valve/valve-piston interference over time as the cam phases to max overlap.

The Ducati.com website shows the *service intervals* as 9K miles or *12 months* and "valve checks" at 18 k.

When Ducati mentions a *time-line* in the service specs, that usually means *belt* change. For example, my st3 needs belts changed at 12 K miles *or 24 months*, regardless of miles.(BTW, went 18 k between valve *adjusts* on my st3)

*If* that's the case with the new DVT engines, (won't know until we know) that means belts on MTS 1200 DVT engines will be replaced *at twice the rate* of other belt driven cam engines.  EEK!  

« Last Edit: October 22, 2014, 03:37:17 pm by st ryder » Logged

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« Reply #3 on: October 22, 2014, 09:05:04 pm »

So this is different from Honda VTEC because the intake and exhaust cams are both variable, whereas VTEC is just the exhaust?  
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st ryder
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« Reply #4 on: October 22, 2014, 09:58:44 pm »


So this is different from Honda VTEC because the intake and exhaust cams are both variable, whereas VTEC is just the exhaust?  

I'm no expert on this technology, or any technology for that matter, but it differs from v-tec in that all valves (8 in the big twin's case) are being used at the same time. The Desmodromic Variable Timing changes the cam's timing from minimal valve overlap at low speeds to maximum valve overlap at high speeds, to maximise smoothness, power output, and mileage. V-tech goes from a 8 valves operating at lower speeds/rpm engine to a 16 valves operating at higher speeds/rpms engine after a certain speed/rpm is reached by actuating idle cam lobes to start driving idle valves.  This is the reason why there's such a backlash against v-tech, because the power "kicks in" when the other cams-valves start being used. The new VFR 800's marketing states the transition has been smoothed out from the previous v-tech. DVT OTOH, is marketed as "infinitely variable" between the min and max valve over lap timing changes, i.e. smooth. Smile
« Last Edit: October 22, 2014, 10:06:01 pm by st ryder » Logged

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« Reply #5 on: October 24, 2014, 12:14:31 pm »

Ducati's variable system sounds a lot like that you'll find in Subaru engines starting in 2004.

http://drive2.subaru.com/Win05_WhatsInside.htm

The cams on the two systems look similar but I haven't anything on how Ducati will control the variable internal piece of the cam gear.  The Subaru ECU uses various sensor inputs to direct a control solenoid that directs pressurized oil which then moves the internal part of the cam gear.  The Subaru system seems to work pretty well.
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« Reply #6 on: October 24, 2014, 02:31:29 pm »

It looks a lot like what is being used on the C14's intake cams.  My memory is that the C14 intake cam timing can vary by up to 23 degrees.
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« Reply #7 on: October 24, 2014, 02:38:32 pm »


Ducati's variable system sounds a lot like that you'll find in Subaru engines starting in 2004.

http://drive2.subaru.com/Win05_WhatsInside.htm

The cams on the two systems look similar but I haven't anything on how Ducati will control the variable internal piece of the cam gear.  The Subaru ECU uses various sensor inputs to direct a control solenoid that directs pressurized oil which then moves the internal part of the cam gear.  The Subaru system seems to work pretty well.
Bill W.



I'm sure the VW/Audi Group will be pleased to hear their system works as well as Subaru's . Smile

Nice post. Smile Those timing graphs sure look the same as "Ducaudi's".
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« Reply #8 on: October 24, 2014, 06:27:58 pm »

What would be good is if the cams location is monitored and the variable mechanism positions the cams independent of the belt – stretch away, no effect on cam timing.
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« Reply #9 on: October 24, 2014, 09:45:13 pm »


What would be good is if the cams location is monitored and the variable mechanism positions the cams independent of the belt – stretch away, no effect on cam timing.


And maybe that's how it will work.  Smile

But I did notice the service intervals are at 9K and *12 months*, (as well as 18 K for shim checks/adjust) and when time line service intervals are mentioned for Ducatis, it means belts, as in time to change them no matter how many miles you have on them.  (for Ducatis with belts that is Smile )  

Maybe they don't need to be changed, just tensioned. Even so, that's a lot of labour every 12 months, *if* they need to be tensioned to keep the valve system running like it should. If you're not doing them yourself, that will add up quickly.  Sad (I'm "into" my belts once a year anyway when I check the shims, but replace them every 2 years)

But, that's all speculation.  Smile
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« Reply #10 on: October 25, 2014, 11:54:19 am »


It looks a lot like what is being used on the C14's intake cams.  My memory is that the C14 intake cam timing can vary by up to 23 degrees.


And doesn't do a damn thing, at least in stock trim.



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« Reply #11 on: October 27, 2014, 10:40:27 am »

Belt tension is probably the big issue.  Obvious to most I guess is that without a automatic tensioner then this isn't much different than what we've dealt with for years.
Bill W.
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« Reply #12 on: October 27, 2014, 06:43:52 pm »

"From a mechanical point of view, the system consists of an external housing, rigidly connected to the cam belt pulley, plus an internal mechanism connected to the camshaft that rotate independently inside the housing. This rotation of the internal mechanism of each camshaft—either in advance or retard—is precisely managed by electronically controlled valves that modulate oil pressure on either side of a three-vane rotor sealed inside the chamber of the mechanism and solid with the internal mechanism of the camshaft. The timing of each cam is dynamically controlled by a sensor located in the cam covers and continuously modulated based on multiple factors sensed by the ECU, with engine rotation speed and throttle position being the most important."

http://www.cycleworld.com/2014/10/27/ducati-desmo-variable-timing-1198-testastretta-v-twin-engine-tech-update/

"This means no fresh charge goes out the exhaust ports, combustion is improved at low rpm, and you’ll find no more “Ducati shudder” when opening the throttle below 3000 rpm."

Who the F "opens up" the throttle below 3K on his Ducati? Certainly not the rider with a modicum of experience with big twins. DVT, another answer for a question nobody asked that takes the brand yet another step closer to killing Ducati character.  Thumbsdown So what's wrong with riding around the engine's character/power curves by keeping her on the boil, and saving yourself all the extra moving parts of DVT...is that so hard to do?  Headscratch

If you want smooth at all throttle opening, buy an electric bike.  Smile
« Last Edit: October 27, 2014, 06:47:45 pm by st ryder » Logged

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Frank,  2005 Ducati ST3(Red!) (Veni, Vedi,...Ducati!)
mugwump58
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« Reply #13 on: October 27, 2014, 08:08:17 pm »

So your not interested in self canceling turn signals I'm guessing. They're for safety don't ya know.  rofl
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« Reply #14 on: October 28, 2014, 11:24:21 am »


So your not interested in self canceling turn signals I'm guessing. They're for safety don't ya know.  rofl


Given a choice between keeping the character of a Ducati engine, (one simply has to be above 32-3500 rpms for smooth acceleration at city speeds, and above 5000 on the highway, which if one's  not already in that range, he can get there with a quick, most times fun, down shift) and ditching the complicated, weight-adding, bound-to-cause maintenance issues/expense DVT, for self-cancelling turn signals, yes, I'd take the self-cancelling turn signals *all day long* and in a heart beat, as they're actually more pragmatic, improve rider comfort and safety at all rev ranges/speeds for a fraction of the cost.  Bigok
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« Reply #15 on: November 04, 2014, 04:09:11 pm »

 :leghump:





http://www.ducati.com/minisito_1106/video/new_ducati_dvt.mp4


cruise control finally  Thumbsup

http://www.ducati.com/bikes/multistrada/technology/index.do
« Last Edit: November 04, 2014, 04:20:50 pm by staedtler » Logged
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