I spotted this video on you tube, it shows an engine system for push rod engines that does not require valve springs. any thoughts on this?
here is the vid if you would like to see it.
http://www…eature=fvw
Ducati Motorcycles has used a similar system for MANY years…The call it Desmodromic valve actuation. The valves can’t float at high RPM… The system pictured on the SBC looked very heavy and not mechanically stable…
I’d have to see it in operation for a 100k miles on a street driven car before having an opinion on it.
About 15 or so years ago some engines were built without valve springs and these used electrically controlled solenoids to open and close the valves. At the time it was claimed this was going to be the cat’s meow but so far it has not taken off; probably due to complexity and the usual, expense.
Yeah, other problems with the solenoid valves as I recall were with reliability and the need for a much higher operating voltage than the standard 12V auto electrical system to deliver the power needed.
Even the Ducati system is not entirely springless. The rocker arms have light hairpin style springs to make certain the valves are seated and seal when closed. Without those springs, the engine won’t idle, or so I hear.
Really though, springs work so well and desmo valve trains are so high maintenance that I think I will stick to valve springs for now.
This discussion brings back memories. My first bike was a 1972 Ducati 250 with a Desmo head. It had springs but it had two rocker arms for each valve - one to open it and one to close it.
I remember the engine would keep pulling (no valve float) right up to 10K rpm. It may have kept pulling beyond that but I don’t remember trying.
Mercedes had Desmodronomic valves on the 1955 300 SLR straight eight. Must have worked quite well because the won a lot of races with them.
Here’s the Ducati valve train. Notice the opening and closing cam lobes and the closing rocker arms. Valve clearance, both opening and closing, is adjusted by replacing shim buttons with ones of a different size. You need to have an assortment of different size shims on hand when adjusting the valve clearance. However, most owners claim that after the initial valve adjustment after break in, subsequent valve adjustments are mostly just valve clearance checks.
It seems evident that a roller lifter setup as is commonly used now will more easily return valve spring energy back to the valve train and subsequently to the engine due to less friction, making the need for an alternate method of actuating engine valves less desirable if fuel mileage is the main goal as it is now rather than absolute maximum power for a given engine size.
Ducati’s desmodromic valve lifting setup is expensive to adjust if you must pay a dealer to do the job.
There was even a desmo conversion for old British bikes.
Actually, the spring that you see on the 2 valve ducati engines is just there to retain pressure on the closer shim so that it doesn’t get beat to death by a loose closing rocker arm. Mostly just to prevent excessive noise.
I have 3 Ducati’s in my garage, and 2 extra that I perform maintenance on every year, and the valve system in the Ducati’s is not only a joy to work on a technical level, but also easy if you can actually add, subtract, and measure a shim with a micrometer.
BC.
Its expensive because of:
1- Its part of a machine made by Italians. The customers expect every single cost associated with an Italian machine to be high. It shouldn’t be, but it is.
2- The name is difficult to pronounce, and sounds foreign. Americans seem to be willing to pay more for something if it has a complex, foreign sounding name attached to it.
3- Most owners of Italian products hate getting their hands dirty, and are willing to shell out lots of money for other people to deal with the un-pleasantries of such things that are beneath them.
4- Some people take one look at the valve train on a Ducati engine, and immediately think its beyond their capabilities. I showed my gf how to measure, choose and change the opener and closer shims on her 97 Ducati Monster 750, and even though she lets me still handle them, she watches me handle them, and will help me choose the right ones every time we work on our bikes, and our friends bikes.
Its really, really easy to work on the 2 valve motors.
The 4 valve motors are slightly harder to take apart, but taking the clearance measurements is actually easier than the 2 valve motors.
BC.
That video looks interesting, but the system doesn’t look to have the ability to do variable valve timing and lift, big requirements these days for maximizing efficiency, power, and economy. Fiat’s ‘multiair’ system looks to have lots of potential:
http://www.themotorreport.com.au/wp-content/uploads/2009/03/fiat_multiair_009.jpg
read more here: http://www.caranddriver.com/features/09q4/fiat_s_multiair_valve-lift_system_explained-tech_dept
The requirements for solenoids were pretty extreme. IIRC, you could spec out some ridiculously expensive solenoids and still half of them wouldn’t meet specs. Nothing like getting rid of $150 in valvetrain parts for $150,000 in solenoids.
On the other hand, if they can ever get the expense under control, it does offer some great advantages - imagine essentially infinitely variable valvetrains that are also cut several inches off the engine’s height (more room to work, more aerodynamic designs, etc…
I have no direct experience Ducatis but I have adjusted clearance on other shim adjusted valve train motorcycles. The adjusting is usually the easy part. The dreaded part is disassembling the bike enough so that you can access the valve train, which on my bike means draining the cooling system, removing the gas tank, a bunch of hoses, disconnecting wires, and on and on.
Gosh how I miss my old Kawasaki KZ 400 where you unscrewed a small valve access cap, stuck in a feeler gauge, and then loosened a lockscrew that let you turn the eccentric rocker arm shaft until the valve clearence was perfect. A 30 minute job from start to finish.
That’s the great thing about the older air cooled Ducati Monster engines.
The Horizontal cylinder head is easily accessed, as it’s right out front.
If it has an oil cooler, your remove 2 screws, and shift it out of the way, and then pop off the access cover.
The Vertical Cylinder was a matter of propping up the gas tank, removing the battery, and then popping off the access covers.
The newer air cooled monsters are pretty much the same for the horizontal cylinder, but the vertical cylinder has become a mess with all the plastic fake gas tank panels, then disconnecting the actual oblong shaped gas tank, then getting the battery and the battery tray mounting bits out of the way, then you finally get to access the valve covers. Then it gets easier.
Great system, as you can have cam profiles with wild lift and closing profiles, as the valves will always open and close on time, regardless of the rpm level.
The 4 valve liquid cooled Ducati engines are a bit more involved.
Actually adjusting the valves requires pulling the cams, but in comparison to an engine that uses a timing chain, the cam belts on the motors are easier removed, and easier to get back in time. You have to go out of your way to screw it up on these engines, and you don’t have to advance the cam slightly before setting the cam chain tensioner like you have to do on so many I-4 motorcycle engines, and then double check the valve timing after everything’s back together, one last time.
BC.
It looks interesting, but I have questions:
Does it use the engine oil system, or does it have its own, separate oil system?
If the oil is common, how small are the passageways, and how much carbon build up from lack of oil changes will it take before the system gets clogged, and no longer works?
What happens if there’s a failure in the system, and the valve either doesn’t open, or never closes? Will valves hit pistons?
If its a separate oil system, what happens if it leaks out, and gets into the engine oil? Will that damage the engine?
I have lots more, but those are the big ones off the top of my head.
BC.