FO2K

I'm a little confused as to what you mean here.



I didn't know someone was using the twin cam technology to close valves. I'm surprised the use isn't more widespread.

Christople

MB pushing new tech like usual

JonBoy

No valve float, but what about throwing a rod? Your connecting rod forces are going to be huge at that size - probably not that reliable for most applications (ie, anything over 1.5L).

Penforhire

We knew this was coming. Prototypes have been around for over a decade and there are some awesomely reliable solenoid valves (they'd need to be here). I still have to believe the early production models will use a non-interference piston/valve design, just in case it fails...

FO2K

Yeah, I agree the bottom end would have to be beefed up, and wouldn't be used in most applications.

Dr. WOT

German electronics controlling my valve train? LOL, no thanks.

ccarnel

I'm going to bet that the "solenoid" is something a bit different than we are thinking. I read an article a while back (for the life of me cannot remember the source) where they were using a magnetorheological or piezoelectric-elastomer to control the valve actuation. Here they acuatly had a working engine using this technology. Initially it did not work well because a single solid piezoelectric elastomer stack did not move far enough when "activating" it with a current. They also had initial problems with the speed of activation.

They wound up using several small disks stacked on top of each other and when activated in unison they were able move the valve far enough to actuate the valve. By vayring the current you can vary how far the valve can move.

I think that this was working a lot better than the electromagnetic solenoids because when a fixed current is applied to the elastomer and it moves some fixed distance but is difficult to compress that elastomer in that fixed position. This system therby uses much less current than an electromagentically activated solenoid

mastamind

LOL, true enough. If VW can't keep their windows from randomly falling off track, how reliable do you think their solenoids will be?

Fencer

Don't hydraulic lifters already exist in Indy racing or have I gotten something mixed up? In which case this infinitely variable valve timing capability already exists they just want to do it with coils now.

fx991

right here i'm pretty much just summarizing an article i've read in Evo mag, and read a couple more over the internet (can't find the links sorry!).

The valvetrain is called desmodromic, and in actual fact it uses 3 camshafts to operate the valve train (1 to open the inlet, 1 to open the exhaust, and 1 to close the valves). The entire assembly is gear driven off of the crankshaft, and all the cams do are push on little rocker fingers. So the inlet camshaft will push on the finger to open the inlet, then a millisecond or so later the exhaust camshaft will open (valve overlap), meanwhile the 3rd camshaft will rotate around and push on another finger rocker to close the inlet valve and then close the exhaust.

The drawbacks to this valvetrain design are that accurate component machining and finishing is difficult, making it exceedingly expensive. And add to that the fact that today's metal valve springs can reliablely rev over 9K RPM (s2000 and various bike engines). Therefore this type of valvetrain is limited in it's use to extreme high speed motorcycle engines.

And i meant that today's metal valve springs have to undergo extreme pressures and forces to be able to compress and expand rapidly enough to keep up with the engine. That a valve with such a small cross sectional area (say of 38 mm) would have to support 225 N of force, would equal a surface pressure of about 30 psi to expand, but then it would have to almost instanteously contract to a negligible pressure. That's where the statment of an enormously powerful pump would be needed.

Hope that helps F02K!

And hey Christople, Mercedes isn't pushing new technology this idea of the camless engine has been around since engine's were born. And the technology and money to tinker around with it and start making prototypes has been around for 20 years. Just noone has really put any effort into it because of the advances in valve spring technology.