What is the primary function of the automotive catalytic converter and exhaust silencer (pot catalytique et silencieux d'échappement)?

1. To convert toxic exhaust gases (carbon monoxide, hydrocarbons, NOx) into less harmful emissions and reduce engine acoustic noise
2. To increase engine horsepower by doubling fuel combustion volume
3. To cool the engine oil during high-speed driving
4. To heat the vehicle interior during cold weather