FO2K

I'm still confused, I was under the impression that the solenoid operated valves would not have valve springs as we know them, so why would the solenoids have to overcome so much force?

mosesbotbol

Didn't Jaguar do something with camless engine technology in their brief F1 stint? I thought they also pressurized the head so the valves would lift easier...

JerryIII

My wife had a 1999 jetta that had this happen 5 times. After the last time, we traded it in on my 1st S.

BPUKiller

You forgot to add,.."and failing miserably." Just look at a Mercedes forums and you will notice most of the post are about electrical gremlins. I think Toyota is ahead of Mercedes in the techno department. Like posted above, I believe I heard car makers are switching to a 42V electrical system so they can support solenoids. This will be wacky crazy news for tuners..I can't imagine all the possibilities. I'm sure all car makers are have systems similar in testing stages because it make so much sense. What might be stoping others from coming out sooner is you have to change the whole electrical system to run with the higher current.


Sam

fx991

okay, sorry F02k, i made a mistake in my conversion from pounds force to Newtons (divided by 4.4498 instead of multiplying). So the resulting pressure would be 568 psi. But that isn't what is really needed here. The huge force comes from the valve having to accelerate and decelerate tremendously in such a small space. These huge accelerations, coupled with the mass of the valves results in the forces that he metal valve springs would have to deal with, mind you i'm no expert on solenoid valves (and certainly don't profess to be), this force could probably be lowered (becuase the fluid in the new valves would most likely be air) do to less internal resistance inside the metal of the valve springs.

But the bigger problem arises becuase of the acutal compressor has to be able to provide those pressures up to 9000 times every minute, which leaves it about half a millisecond to react. And in this time it has to pressurize enough air to provide the force necessary to close the valve again, whereas opening the valve is relatively easy (just a pressure relief valve). The high power rating on the compressor results from the incredibly high mass flow rates that are required to pump the air into the valve and push it out at the required times. At intervals, and that is the key part, is the pump has to push the air in at intervals, in F1 engines (as i understand it) they have the pump constantly pushing air into the valves, with a camshaft pushing the air out of the valves to depress them. A way to reliably open and close valves at a regular pace for production engines still hasn't truely found its way. But i'm rambling on terribley now, and i hope sincerely that that all makes sense!

protokultur

This is very interesting new tech - aluminum block diesels and now camless actuated valves in production cars.

The biggest benefit of the solenoid is that there are no valve springs, which are just as stiff at idle as they are at redline, leading to inefficiencies either at the top end or the low end (depending on how the engine is optimized). So if your car is idling in traffic, something like a quarter of the losses could be due to pushing the very stiff valve springs. This has big implications to limited duty ICE designs like hybrid or lean burn.

There have been racing engines with hydraulic or pneumatic valvetrains, no real reason to use them on production vehicles as there are still the springs. Desmo can help out at the high end, but really is most useful when displacement cannot be easily increased as is the case in formula racing or bikes.

protokultur

Also regarding the valve kinetics issue, read here:

http://www.memagazine.org/backissues/may03...controlled.html

WhiteS2k

Can't help but notice that the article was dated July 2005. So does that make this old news?

cutes2k

Weren't BMW testing a pneumatic setup?

Ed_Grant

==What might be stoping others from coming out sooner is you have to change the whole electrical system to run with the higher current.


Sam==

Actually the wiring can be lighter as higher voltage means lower current for the same power. A weight savings. That's one reason that aviation went to a 24 volt system a long time ago.