funny-i remember talking to some friends about using solenoids to drive the valves in a car back when we were in engineering school.....we thought the electronics would be kind of a pain. the timing would probably be controlled more efficiently though.
From NY Times, Cam-less engines:
>
> WHAT'S NEXT
> A Chip-Based Challenge to a Car's Spinning Camshaft
> By IAN AUSTEN
>
> F Henry Ford could see the engines now made by the company he founded
> 100 years ago, he would probably be puzzled by the electronics that
> control many operations. But the mechanical system operating the valves
> that bring fuel and air into the engine and let out exhaust would be > very familiar.
>
> As in Ford's time, those spring-loaded valves are opened and closed by
> cams, precisely shaped bumps of steel spinning along a rotating shaft. >
> But some automotive researchers are working on ways of making mechanical
> valve controls as obsolete as the Model T Ford. Operating the controls
> electronically could improve fuel efficiency, reduce emissions and
> perhaps even eliminate the need for spark plugs in gasoline engines. >
> The demise of the camshaft would also be welcomed by companies that make
> electronic parts for cars. "We'd really like to see this technology come
> along because it requires a huge use of semiconductors," said Ray
> Cornyn, the manager of Motorola's microcontroller division in Austin,
> Tex., which supplies the auto industry.
>
> Over the years, electronics have been more of a boon than a threat to
> camshafts. Computer-controlled manufacturing systems and computer-based
> designs have improved the quality of camshafts while reducing the cost
> of their manufacture. But in concept, camshafts remained relatively
> unchanged from the era of Ford's first assembly lines.
>
> Today it is common for each cylinder of a car's engine to have two pairs
> of intake and exhaust valves, with each pair sharing a cam on the
> camshaft. The camshaft is set spinning by a rubber belt or steel chain
> connected to the engine's crankshaft, the component that ultimately
> provides the power to the car's wheels. As the camshaft rotates, the
> high point of each cam first presses against a spring-loaded lifter of
> an intake valve, gradually opening it, and then closing it as the cam's
> low side approaches. As it continues to revolve, the high part of the
> cam repeats the process for the paired exhaust valve.
>
> When Siemens VDO Automotive, in partnership with BMW, built a prototype
> camless engine four years ago, it came up with a three-part system. In
> place of cams it used solenoids, electromagnetically controlled plungers
> that are already widely used in cars for things like electric door > locks.
>
> While an electronic valve control system doesn't need mechanical power
> from the crankshaft, it does need to know what the crankshaft and the
> pistons driving it are doing. In a normal car, the belt or chain that
> connects crankshaft to camshaft ensures proper timing; that is, no valve
> remains open when its cylinder's piston is at the top of its travel.
> Such a situation would seriously damage a motor.
>
> In its camless version, Siemens prevents such mistiming by using sensors
> that detect the position of the crankshaft and thus the pistons.
> Finally, the new engine was given yet another powerful computer to make
> sure everything works in sequence. "When an eight-cylinder engine with
> four valves per cylinder is running at 6,000 r.p.m. there's a lot to
> do," said Michael Gauthier, director of corporate technology in
> Siemens's automotive division.
>
> The prototype engine was installed in a 3-series BMW sedan. It worked
> but had several significant shortcomings. For one thing, the solenoids
> and the additional computer power taxed the car's already overburdened
> electrical system. Mr. Gauthier said that cars would have to make a
> long-awaited move to 42-volt electrical systems (from the current 12
> volts) before electronic valve control would be practical.
>
> For car makers, the system's least attractive aspect was its price
> relative to camshafts. And there was a problem that made the engine
> unattractive to buyers, particularly those who associate BMW with
> smoothly running engines. As anyone who has opened a car with electric
> locks knows, solenoids are far from silent. "I saw the vehicle, and all
> you heard when it was running was slap, slap, slap," Mr. Gauthier said. >
> Motorola believes that the control computer could be programmed to
> soften and quiet the action of the solenoids. Other electronic
> valve-control designs have relied on different parts to push the valves > open.
>
> A device that used piezoelectric crystals, which produce electricity
> when bent, was quiet and cut the power burden. But current piezoelectric
> devices must be about 8 to 10 inches high to operate engine valves. The
> result, Mr. Gauthier said, is an engine "that looks something like a
> porcupine" and will not fit under the hood of most cars.
>
> There are several incentives for trying to perfect electronic valves.
> Among other things, it would allow engines to reduce their power after
> getting a car up to speed, an easy way to save fuel. "About 90 percent
> of the time you need about 20 percent of the engine's output," Mr.
> Gauthier said. "It's extremely wasteful to put a 200-horsepower engine
> in a car when you only need 40 horsepower most of the time."
>
> But some car makers have already found several ways to achieve that goal
> mechanically. Some engines have camshafts that can be raised or lowered
> between two positions to adjust the valve openings. A more sophisticated
> system from BMW can make a wider range of valve adjustments to reduce or > boost power.
>
> Because of those mechanical advances and the cost issue, Zoran Filipi,
> an associate research scientist and the assistant director of the
> University of Michigan's automotive research center, said that
> electronic control would probably become widespread only if it could
> change the way engines operate.
>
> A potential way to reduce emissions and improve economy in gasoline
> engines would be to eliminate spark plugs and, like a diesel engine,
> ignite fuel through the compression of pistons. Such engines, however,
> would only be cleaner if they used a carefully blended fuel mix injected
> at the last moment. Dr. Filipi said that electronic valves might be an
> effective way to control the engines' operation.
>
> The biggest hurdle for electronic valve controls may be that when it
> comes to auto parts, age does have its advantages, said Dr. Filipi.
> "Over the last 100 years or so we've perfected camshaft technologies," > he said.
>
>
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