What is valves on cars?
Valves control the in-flow and out-flow of fuel, air and exhaust
fumes in a combustion engine (known as intake valves and exhaust
valves). A 4-cylinder engine with 16 valves will have 4 valves per
cylinder, with two intake and two exhaust valves per cylinder. With
experience it is easy to tell the sounds of the valves apart
because each engine sounds different with different valves.
Generally the less number of valves means a deeper/throatier
sound from the cars and vice-versa