Differences between 2-valve and 4-valve engines:
* Power output: 4-valve engines generally produce more power than 2-valve engines, due to the increased airflow and improved combustion efficiency.
* Fuel efficiency: 4-valve engines are typically more fuel-efficient than 2-valve engines, due to the more efficient combustion process.
* Emissions: 4-valve engines produce fewer emissions than 2-valve engines, due to the more complete combustion process.
* Noise: 4-valve engines are typically quieter than 2-valve engines, due to the reduced valve train noise.
In general, 4-valve engines are more efficient and powerful than 2-valve engines, and are therefore more commonly used in modern vehicles. However, 2-valve engines can still be found in some older vehicles and in some commercial vehicles, due to their simplicity and lower cost.
