4.5.11.b Zero height cams
In case if not all the engine power is used, then why should all the engine cylinders work? What if just take and disconnect, for example, for a car waiting in a traffic jam, two of the four cylinders?
After all, a pair of cylinders is quite enough for the engine to idle. The remaining two cylinders are no longer supplied with fuel and, so that they do not waste air through the intake and exhaust manifolds, the intake and exhaust valves are closed. In order to perform such a simple operation, they came up with a relatively simple solution: cams with "zero height" were placed on the camshaft, next to the usual cams. That is, they do not affect the valve push rod in any way.
Thus, during normal operation, the camshaft rotates and all the valves fulfill their purpose. When it is necessary to turn off the latter, a special valve opens. Through this valve the engine oil under pressure acts on the camshaft and displaces it in the direction of the longitudinal axis. Cams with a regular profile opened and still open the valves. At the same time the cams with "zero height" simply do not reach the valves, and they, in turn, stand motionless.
Note
Various companies at different times have suggested several schemes for the implementation of the above operation in order to turn off part of the valves. The aforementioned method is just one of the ways.
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