More about it and how it works here : Ducati Reveals Testastretta DVT Engine + Video » Motorcycle.com News
from memory so dont shoot me down. it varries the oil pressure to the cam lifters to varry the lift. also varies the cam drive gear via oil pressure being distributed vie a solenoid
It looks to me that they are using oil pressure controlled by a solenoid to advance or retard each camshaft, it does to effect lift at all. Seems they monitor each camshaft with a sensor and are able to set the timing where they like. Simples. Not sure about worlds first though.
So that'll be the engine in the new Multistrada that was spotted then.... Maybe finally ridding us of the low speed fuelling issues. Maybe. ;-)
http://www.volkspage.net/technik/ssp/ssp/SSP_246.pdf FYI, this is a document released by Volkswagen in 2001 explaining the VVT system they introduced on cars at that time, in fairly simple terms. It is a five-flute system, but otherwise appears similar to the three-flute system Ducati are now introducing. It changes cam-phasing (i.e. timing and overlap) but not valve lift or duration, using solenoid-controlled oil pressure. In the VW system the whole VVT mechanism is within the oil envelope of the engine, so a minor oil leak would not be significant, but in the Ducati application the mechanism is in the belt pulleys and thus dry (outside the oil envelope). Any oil leak would be serious, so they must be confident they can keep it oil-tight.
The world's first desmodromic VVT. Dozens of firms have made millions of VVT engines, but not desmos.
Where the camshaft is supported in its bearings, in addition to the oilway hole feeding oil at constant pressure to lubricate the camshaft bearings, there are two further oilway holes feeding oil at variable pressures into two galleries machined into the camshaft between the bearing and the toothed belt pulley. The pressurised oil in those two galleries is linked through drillways into the VVT unit which is mounted on the end of the camshaft, housed within the pulley. The oil for the VVT system is bled off the ordinary lubricating oil system of the engine, and the pressure is controlled by a solenoid attached to the side of the cylinder head; the solenoid is controlled electrically by the engine management system just like the fuel and spark. For a Vee twin engine with DOHC, there are four VVT units in all and four solenoids. All the oil seals had better be good!
Excellent explanation Peter, exactly the concise explanation I was after. Many thanks for that. It seems so practical, that I am surprised they haven't brought this out before, as the advantages of being able to control the valve timing are so beneficial.
here is a bit more about vvt and multi air. hydrolic vvt has been around a very long time, my experience suggest it's v.reliable. seen several volvo systems fail and one fiat fail never an oil leak, never caused a break down can cause a rattle at tick over Inside Fiat’s innovative MultiAir system - SAE International
cool,cool. in what way tho, couldn't get it from the promo. diverting oil pressure to advance or retard a pulley using a solenoid valve via a map in the engine ecu. all sounds the same to me.
You have just described the VW/Ducati system, but not the FIAT system. The FIAT arrangement is that it is the tappet between the camshaft and the valve which is hydraulically variable, not the rotation of the camshaft.
ARE you sure? you have got me thinking now. the original system thats been around since all the 155 models came out back in 99? all had VVT hydraulically operated cam pulleys. sure of it.
