I know the theoretical advantage of desmodromic valves....basically no valve bounce /increased rpm.But in the real world,conventional valve actuation is less complex and have higher rpm.So,whats the point?
Faster valve opening speeds that conventional valve gear. Much reduced frictional losses in the valve gear. Compare turning a desmo camshaft system with a valve spring system.
Desmo cams turn easily by hand,but so what.If they rev to 20000rpm then okay,Icould see why they are used.It just seems a non solution ,if you know what I mean.
The cam profiles in high speed valve-spring engines have to be designed in such as way as to avoid valve float, given the limitations of valve springs. In a desmo engine, valve float is not an issue, so the designer has more latitude with the cam profiles. The result of this is that more advantageous profiles from the perspective of gas flow are possible in desmo designs. Why would Ducati relinquish this now, after spending 50 years accumulating a unique body of expertise in cam design?
in F1 they drive the valves with air to get to 20k so its a good system and alot less hassle than air.
Its just that suzuki ,with the TL motor achieved similar if not more power,with conventional valve drive system.
Engine rpm is limited by the mass of the Pistons/crank assembly. A twin will never Rev like a IL4 for a given cc because the Pistons are so much larger/heavier. Desmo allows very fast valve opening to full lift and back to closed again to allow good cylinder fill. On the 4v motors it gives that control to both cams so you can run the overlaps pretty close. Its also pretty efficient so there's less power lost turning the cams and more to go to the back wheel I think back in TL days, development was where it was and suzuki did a pretty decent job. There was nothing ground breaking, they just applied themselves well to the TL. Honda turned out a good un to. Remember that back then the Japs quoted crank whereas Ducati were quoting rwhp
They also achieved an engine with a tough gearbox and tough crankcases. If they had of developed that bike it woukd have been amazing in wsb. As it was rule changes allowing 1k 4cyl killed it before it started
Pity sleeve valves never caught on always thought they were neat. I know I know you'd need a BIG starter motor to overcome the stiction and they had their own disadvantages. I just always thought mechanically (but mot materially) they were rather elegant. Sorry Off Topic (AGAIN)......................waits for the hammer from El T
Just to add my 2 peneth worth. Desmo allows precise timing at silly revs with minimal losses. I remember Hodgsons 996 running to about 13800 rpm. TLs though DON'T have strong gearboxes, they're actually a known weakness, and the cases start to distort around 150-160 bhp so they're not too clever either. I love mine though, and wouldn't have had the same fun as cheaply on my Ducati.
In F1 they close the valves with air springs, i.e. instead of a steel closing spring there is a sealed capsule of high pressure air. Air has a lower reciprocating weight than steel. No-one has yet produced an air spring system reliable enough and long-lived enough to use in road vehicles - unlike desmodromics. Not every engine is designed to extract the absolute maximum power from that capacity. There are other considerations.
Im not in any way trying to "dis" ducati or their system,Im just trying to get my head around why they bother with desmo when there is no real world benefit.Its a fine way of opening and closing valves,in theory.No valve float,almost limitless rev ceiling,not to mention any thing else.Is it just being different for difference sake?
It wasn't once, but I fear it is now.... more costly to set up and maintain. Aside from examples like KTM and Aprilia, my guess is that the Japanese could produce designs to compete with Ducati but I'm sure they'd stick with conventional springs. With motorcycles (when you compare them to most cars, anyway), the engine design has always been more visible and the internals of more interest to many of those who ride them. The Ducati 90 degree layout and desmomdromic valvegear, and avoidance of chain drive to camshafts are all to some degree "branding" - which is not a criticism. Harley Davidson of course go to the other extreme - rather than saying "look how clever our valve gear is" they continue to use push-rod designs, apart from the unusual V-rod (which is DOHC I believe).
Yeh loved mine too. Remember reading when the bike was conceived the goal was to homologate a bike which could be good for about 185hp as it were at the time. So will have to agree to disagree on the finer detail
Not quite dead OldJock rcv_engines_ltd If you're really interested about sleeve valve engines. http://www.enginehistory.org/members/articles/Sleeve.pdf
