xviper

Technology costs. How much do you want to pay for these cars and how much are they going break down especially when they're new?

cthree

[QUOTE]Originally posted by xviper
[B]Technology costs.

S2kRob

Once again, UL has hit the nail on the head.

A couple of things that I would like to add are:

1) The BMW system will actually make its debut on its new 4 cylinder engine line in the next two years. The system is designed more for fuel economy than for ultimate power. These engines will have NO THROTTLE BODY!!

The way the system works is that a lever is inserted in between the cam and the valvestem. The lever essentially can control the lift of the valve, while the cam controls the valve opening profile. The lever's position is controlled by engine oil pressure, similar to the VTEC system.

In brief, under light throttle, valves do not need to fully open to allow the required mixture of fuel in the combustion chamber. In light throttle, the lever would allow a minimum of valve opening so that a small amount of fuel/air charge enters the engine.

Under heavy throttle, the lever moves into a position to allow 100% opening of the valves according to the cam profile. This allows the maximum air/fuel charge in the cylinder generating full power.

You will note that this system makes the throttle body redundant.

BMW claims fuel economy increases of over 10% with this system.

Should be interesting when it goes into production.

2) The other point I wanted to clarify is that F1 engines require pneumatic valve systems because at the incredible revs the engines run (18000+rpm), a steel spring is insufficient to combat valve float. Valve float occurs when the valvestem actually stops following the surface of the cam and stays open, or floats. This can cause interference with the pistons as they move on their compression strokes.

xviper

I don't dispute that technological innovations are inevitable, but it does cost. When you built a car with a carb you need a carb, low psi fuel pump. Built one with fuel injection and you need injectors, fuel rail, high psi fuel pump, fuel pressure regulator, a multitude of sensors and an ECU. This stuff is way more money. True, down the road, you'll get a more efficient and economic engine but your initial buy-in is much higher and that's what I'm talking about. The manufacturer isn't gonna give ya this stuff for free. And more times than not the first while after introduction into the market place there are bugs to work out. Look at our own car. Reports dealing with clutches, gear grinds, rear diffs, #4 cylinders, oil use, etc. I think the S2000 is cutting edge compared to other stuff out there. Think of any "last" generation 2 hundred & something HP car (Vette, Mustang, Camaro). These cars were primitive by comparison but they didn't cost anywhere near as much as the S. Our car isn't gut wrenchingly expensive but it isn't cheap either. High tech is great but you get to a point where the end does not justify the additional cost. Oh sure, the tech will be there one day and those wanting it will have to pay for it. If it gets too far ahead of the pack, tech speaking it'll just price itself out of many peoples' reach.

cdelena

[QUOTE]Originally posted by S2kRob
[B] The BMW system will actually make its debut on its new 4 cylinder engine line in the next two years.

ultimate lurker

Yeah, pneumatics don't suffer from the stress induced failures that springs do at those rpms. However, I will point out that CART engines rev near 17k rpm with springs, and modern 600cc motorcycles are exceeding 15k rpm in production applications, so the springs have a long way to go and probably won't be replaced by pneumatics in a road car any time soon. The key is material control and very precise spring wire profiles.

On the valve float front, some companies are looking at ways to take advantage of this. Ferrari has released information on something they are working on called a "ballistic" valve train. Essentially, at low rpm, the standard springs would be able to control the valve motion. But as rpms climb, the cam ramp would be designed to get consistent float by "throwing" the valve off the cam face as you near peak lift and then catching it on the way back down. This would create naturally increasing lift (but not duration) as rpms climb. Kind of interesting, but not unusual to see someone take what was once considered a design flaw or failure, and with the careful application of technology and control, turn it into a useful tool (controlled burns for forest fires, nuclear power plants, fractured metal connecting rods, etc.).

And cdelena, you're absolutely right. The more things change, the more they stay the same. Many "new" technologies have been tried in the past, its just that now improvements in materials, design simulation and control have allowed them to actually be effective in modern applications.

UL

2kturkey

[QUOTE]Originally posted by ultimate lurker
[B]There is a company here in the states which already has such systems running on road vehicles in a prototype stage.

Clark

Just a little more info on the "camless" engine design. The diesel application that UL referred to is an engine developed by International, formerly known as Navistar.

Clark

solo2racer

The other problem that occurs with a EMV system is that you have to slowly lower the back back into it's seat, or the mechanical stress will damage the value and the seat.

With a cam, you get the soft close for free as the valve follows the cam profile. With an EMV system, the solenoid has to fire to open the value, and another system is needed to slowly close the value in a controlled fashion.