Exhaust Collector
The junction point in an exhaust system where the multiple runner pipes of a manifold merge into a single pipe.
An exhaust collector is the final section of an exhaust header or manifold where the individual exhaust runner pipes from each cylinder merge into a single, larger outlet pipe. Its primary function is to gather the exhaust gases expelled from each cylinder and direct them into the rest of the exhaust system, including the catalytic converter, resonator, and muffler.
The design of the collector is critical for engine performance. In headers, the collector's shape and diameter are engineered to optimize scavenging—a process where the high-velocity exhaust pulse from one cylinder creates a vacuum behind it, drawing out the remaining exhaust gases from the next cylinder in the firing order. A well-designed collector improves volumetric efficiency and engine horsepower.
Exhaust collectors are subject to extreme heat cycles and road moisture, making them prone to rust and thermal cracking. Leaks at the collector flange or welds are common and will cause loud exhaust noises, loss of engine backpressure, and potentially draw fresh air into the exhaust stream. This air can throw off oxygen sensor readings, causing the ECU to run the engine rich.