Camless Engine Technology
The camshaft in the engine of most motor vehicles performs the function of opening the intake and exhaust valves at the appropriate times. There are engines with a single camshaft which activates the valves through the mechanism of a valve lifter, pushrod and rocker shaft; and there are overhead cam engines which have the cam(s) located in the engine head. The classic American V-8 traditionally is of the pushrod type, while many higher performance engines use single or multiple overhead cams.
The camshaft was, for many years (and still is in many cars) directly driven from the crankshaft by chain or belt. This fixed relationship dictates that the opening and closing of the valves has a fixed relationship to the position of the piston in the cylinder, with the timing of the spark plug firing (known as spark advance) being the only variable in the combustion process. This means that the design of the camshaft factors which activate the valves, like timing, duration and dwell were by necessity a compromise based upon the requirements for starting, idling and output performance. Higher performance engines have camshafts which are designed and optimized for specific power ranges and purposes, which is why a traditionally souped-up engine optimized for higher rpm and torque normally idles more roughly and/or at a higher rpm.
Some more modern cars use a variable timing system which allows the camshaft lobe relationship to the piston location to change based upon the engine rpm and other power demand factors. This has an advantage both in the area of performance and fuel economy and efficiency, because the cam design is no longer restricted to a single relationship and can be optimized over a greater performance range. Most cars with this feature are of the dual overhead cam design type, so the ability to change the timing between the closing on the intake valve, spark plug firing and opening of the exhaust valve for waste-gas scavenging can be changed fo meet the needs of a variety of engine speeds.
Formula 1 cars, for several years, have evolved into an engine design which eliminates the camshaft altogether, and uses the application of individual actuators for each valve. This design freedom now allows the engine designers to precisely computer-control exactly when they want each valve to open and close (and how much to be open) with no direct mechanical relationship to crankshaft and piston location. The only hard constraint (which is a good one to remember) is that care must be taken to ensure that a valve and a piston never try to occupy the same space at the same time.
The mechanisms used to individually control these valves vary (hydraulic, pneumatic and electric), but the advantages in power output far exceed those under the fixed timing constraints of traditionally cammed engines. While the durability of these individual valve actuators still requires some work in order to make them suitable for prolonged use in street engines, the future possibilities of this technology are very exciting indeed. The engine control computer is then able to monitor a wide variety of factors and be programmed to tell each cylinder and each valve exactly when to open and close based upon the power and fuel economy profile needed at that instant. Individual cylinders can be deactivated in a similar manner to some engines of today, but with much greater freedom than the current eight-four valve lifter deactivation mechanisms provide.
One can envision a car which has a simple dial control on the dash which enables the driver to select from a range of power and fuel economy settings as they desire. This possibility makes the performance enthusiast drool, but in reality the greatest opportunity for this camless engine technology should be to move the fuel economy performance of the average car into a new level without the necessity of converting the entire national infrastructure over to a new fuel system. For overhead cam engines, one could foresee the potential to modify an existing engine with a new cylinder head and computer module in an existing vehicle as well.
