this design is very suitable for high power outputs. Five-valve cylinder head Less common is the five-valve head, with two exhaust valves and three inlet valves. All five valves are similar in size. This design allows excellent breathing, and, as every valve is small, high RPM and very high power outputs are theoretically available. Although, compared to a four-valve engine, a five-valve design should have a higher maximum RPM, and the three inlet ports should give efficient cylinder-filling and high gas turbulence (both desirable traits), it has been questioned whether a five-valve configuration gives a cost-effective benefit over four-valve designs. The rise of direct injection may also make five-valve heads more difficult to engineer, as the injector must take up some space on the head. After making five-valve Genesis engines for several years, Yamaha has since reverted back to the cheaper four-valve design. Examples of the five-valve engines are the various 1.8 L 20vT engines manufactured by AUDI AG, the later versions of the Ferrari Dino V8, and the 1.6 L 20-valve 4A-GE engine made by Toyota in collaboration with Yamaha. Beyond five valves For a cylindrical bore and equal-area sized valves, increasing the number of valves beyond five decreases the total valve area. The following table shows the effective areas of differing valve quantities as proportion of cylinder bore. These percentages are based on simple geometry and do not take into account orifices for spark plugs or injectors, but these voids will usually be sited in the "dead space" unavailable for valves. Also, in practice, intake valves are often larger than exhaust valves in heads with an even number of valves-per-cylinder: 2 = 50% 3 = 64% 4 = 68% 5 = 68% 6 = 66% 7 = 64% 8 = 61% Alternative technologies Turbocharging and supercharging are technologies that also improve engine breathing, and can be used instead of, or in conjunction with, multi-valve engines. The same applies to variable valve timing and variable-length intake manifolds. Rotary valves also offer improved engine breathing and high rev performance but these were never very successful. Cylinder head porting, as part of engine tuning, is also used to improve engine performance. Cars and trucks Before 1914 The 1908 Ariès VT race cars had 1.4 litre supercharged single cylinder engines with four valve per cylinder desmodromic systems. (Source: [1]) The 1910 Isotta-Fraschini Tipo KM had a 10.6 litre inline 4 with single