Donster

NickdaBrick

I think it's a great idea. With infinitely variable valve timing, an engine could be tuned for optimal low, mid, and high rpm power. Furthermore, without mechanical ramps, valves could be whacked open and slammed closed as quickly as they needed to be, with no worries about valvetrain wear.



The first application will probably be in some big, bucks-up V-Twin cruiser, for two reasons: First, emissions control, and second, because big-piston engines run slower. It sure would be cool to have a bike that pulled like a tractor at low RPM and screamed like a Gixxer up top, with no weak spots anywhere in the powerband.

Whammo

http://www.eetimes.com/story/OEG20000414S0050



Check it out. I hope this will help.

Patrick-of-the-Hills

Only if it's a Lucas system.

hindle

I heard of an even more way out there engine design that doesn't have any valves at all. No cams, chains, belts, valves, rocker arms, pushrods, etc..... Just a crank, rod and piston.



Can you say 2-cycle?



HeHeHeHe.

hackfu

While Honda's VTEC system is pretty trick, for standard cam system technology, Ferrari has a better system. They have a cam shaft that has really wide lobes. These lobes are different in profile on the different edges and smoothed out inbetween.



Anyway, the cam shaft can slide lateraly (with respect to the valves) along its rotational axis, thus effectively changing the cam profile. One end of the cam is "sedate" mode, the other end is "ultra-aggresive" mode and the cam can slide between the two and all points inbetween.



I don't think I explained it very well... but I hope you get the idea.

granny

Another point; if this were to happen, the entire engine would be programmable. Every aspect of the basic design of the engine (bore/stroke, rod length, port design etc.) could be optimized for greater power - or not.



Think about the British proposal that will force all vehicles to include GPS systems that would locate the vehicle on computer geographical maps annotated with speed limits. The intent of this system is for the engine controller to enforce speed limits. It does this by comparing the current speed to the posted speed limit indicated by the computer map according to the current GPS coordinates and dialing back the throttle as needed. This is not a rumor, this is real.



While such systems would show up on cars first, it would eventually show up on bikes (can you say throttle chop?).



Freaking politicians could earn loads of brownie points by programming the power of your sport bike downwards since they could easily convince the sheep - er, their constituents that powerful sport bikes are bad. Forget about trivial constraints like header bolts that can't be removed, we are talking about dynamic speed/acceleration control. It could happen, the technology for such a system exists.

Lincoln

jeez, that's a depressing scenario. God bless freedom-loving people everywhere

granny

The 2001 Porsche Turbo Carrera is similar, it has two lobe profiles and has a means to switch between them. Basically, each "lobe" is actually three lobes. The center lobe is the low rpm lobe while the outer lobes are the high range lobes. These three lobes are about the same width overall as a traditional lobe.



The trick (and it's a neat one) is in the lifters. A single lifter is actually a concentric pair pair of lifters. The "outer" lifter is essential a tube that the inner lifter rides within. The inner lifter actual moves the valve. The inner lifter sits on inner lobe (which is of lower lift and duration than the outer lobes). At low RPM, the outer lifter riding on the high duration lobes just wanks off the inner lifter not contributing to valve lift.



However at a mid-RPM point, hydraulic pressure is used to pop out a pin within the inner lifter that lock the inner lifter and outer lifter together. Now via the pin the inner lifter is actually raised by the outer lifter (which in turn is actuated by the higher lift/duration outer lobes) to give higher lift (pretty damned clever, it could only be designed by a male .



In addition to this, the entire cam assembly timing varies (mechanically) according to RPM. The whole package works well giving a very smooth torque curve and very tractable power low speed power. I would think that the Ferari cam design would be a bit to machine. Leave it to Porsche to design it the easy way.

stevegrab

And if they're doing it in a Formula One engine, you can bet that going to hi revs is not a problem. I thik current red line on an F1 engine is on par with top sport bikes like the R1 (15,500) or even higher.



It all sounds very interesting, could make for some interesting developments, especially if Honda gets involved.