What device is primarily used to expel exhaust gases from the engine?

The exhaust manifold serves a critical role in a vehicle's engine system by collecting exhaust gases from multiple cylinders and channeling them into the exhaust system for expulsion. This component is typically located directly on the engine block and is designed to withstand high temperatures and pressure. Its primary function ensures that the exhaust gases generated during combustion are effectively routed out of the engine, which is essential for maintaining optimal engine performance and reducing the likelihood of harmful emissions.

The other options, while important in different contexts, do not directly perform this function. The exhaust port is simply an opening that allows gases to escape but does not play an active role in the collection and expulsion process. The PCV valve, or Positive Crankcase Ventilation valve, manages gases from the crankcase but is not involved in handling exhaust gases directly. A coil spring is a suspension component entirely unrelated to exhaust systems. Understanding these roles emphasizes why the exhaust manifold is the fundamental device for managing engine exhaust gases.