Engine concept

[elgemcdlf]

The new GM truck commercial got me to thinking. The say they have variable valve timing. I have no idea how they do it but my mind got to going. What about eliminating the camshaft, timing set, push rods & rocker arms? Mount motors in the top of the valve covers for each valve. Time the valve motors to the crankshaft just like ignition. Since all this would be run through the computer system you could just write in your "cam" specs. With less moving parts you would have less friction thus in theory more hp without doing anything differently other than the removal of the parts.

I would guess oil would no longer be needed in the upper end. Naturally we couple this with port injection. What do you guys think?

[chad67]

It sounds good in theory, but that will be one more thing I couldn't fix on my own! All kidding aside, I would think it could be done. I remember reading several years ago about someone using rotary valves that had "windows" that would line up with the ports as they turned and "open" the chamber to the port. I haven't heard much about them, but the benefit was supposed to be nearly unlimited RPM's as far as valvetrain is concerned. I would think it may be an issue to find an electric motor/solenoid that could open and close the valves quickly and accurately enough to rev very high.

[Ranchero50]

It'll be here within about ten years.

Variable valve timing can be achieved via using oil pressurized pistons to shift the timing chain guides so it advances or retards the timing. There are other ways via the cam sprockets as well.

[mrollings53]

Why not just hydraulically control the valves. Instead of a rod end you've got the valve.

[DuckRyder]

Electric and/or pneumatic valves will be here, it really wouldn't surprises me if someone in F1 or GP motorcycles has a running prototype...

I think most production VVt schemes out there right now use oil pressure controlled cam sprockets (AKA "phasers" not the star trek kind) and can be either intake cam only or intake and exhaust in DOHC engines (Example BMW "double VANOS").

Honda's implementation (least on the first SOHC) actually has 2 rocker arms and 2 cam lobes for the valve which is to vary, oil pressure drives a pin which locks the two rocker arms together when its time to use the higher lift cam lobe...

[motzingg]

I did some work in college on a system that was hydraulically actuating valves using oil pressure, no cam whatsoever.

they can get it to work but not at very high rpm. the time required to switch a circuit, move a coil, open a valve, open a larger valve, pressurize a chamber, push a valve open... its all happening pretty fast at 3000 rpm.

i'm sure it will happen eventually, piezoelectric valves are getting more and more powerful.


in the mean time, direct fuel injection like in the EcoBoost and others is pretty remarkable stuff.

[mrollings53]

I think the problem with the hydraulic systems using engine oil is the low pressure. Use a separate system with a high pressure pump, and the time to actuate a valve is cut to milliseconds. Leave the valve spring in there, or use the springs from NASCAR engines to keep things less complicated. You get VVT that can be controlled independent of the rest of the motor, and eliminate valve float by using better springs. Only cons I can think of is the amount of electricity required to run the pump, and what will need to be done for initial startup. Either the pump will have to pressurize the system before each start, or an accumulator will be needed to provide the initial pressure for start up.

[deeznuts08]

Koenigsegg already developed said technology http://youtu.be/Bch5B23_pu0