Some of mechanical engineers know better than me in this regard if they come to this forum topic here.

What i know is that Valves just spray the fuel in the cylinder before ignition, the more their nos the better the sequecing of spraying the fuel for ignition at the right position of piston.

More the no of valves the better is the performance of the engine and better ride it imparts to the vehicle but greater is the fuel consumption at the same time.