The timing diagram points out in degree crank angle, when exactly the intake valves and exhaust valves open and close.
Analysing the valve timing diagram it is possible to get a clear insight into the engine characteristic. An engine which reaches its highest torque and its highest performance at relatively low revs, the inlet valve opening, inlet valve closing, outlet valve opening and outlet valve closing are positioned near to the TDC or BDC:
Very sporty engines or even racing engines feature clearly higher values. The valves are kept open for a longer period of time, the valve overlap between inlet valve opening and outlet valve closing is bigger. Modern engines feature a camshaft adjustment. In this case only areas for inlet/outlet valve opening/closing can be defined. The valve timing diagram becomes less important. 06/08