Exhaust Systems

The exhaust system refers to the mechanism which conveys the burnt gases from an internal combustion engine and typically includes a collection of pipes. In the most basic sense, the exhaust system just vents waste gases from the engine. more...

Depending on the overall system design, the exhaust gas may flow through a turbocharger to increase engine power, a catalytic converter to reduce air pollution, and a muffler to reduce noise.

Terminology

Manifold or header

In most production engines, the manifold is an assembly, often cast iron, designed to use the least metal (for the lightest weight) and to occupy the least space necessary to collect the exhaust gas from multiple cylinders and combine those flows into a single pipe. The weight and space restrictions often result in a design that does not do the most efficient job of venting the gases. For example, pressure waves generated by gases emerging from one cylinder may arrive at another cylinder at a point in time that prevents that second cylinder from purging as completely as it might.

A header is another name for a manifold, but refers to an enhanced manifold for which the engineering parameters have been shifted from concentrating on weight and size to concentrating on the optimal flow of the exhaust gases, a process called scavenging the exhaust from the cylinders more thoroughly. Headers are generally circular steel tubing with bends and folds calculated to make the paths from each cylinder's exhaust port to the common outlet all of equal length, and joined at narrow angles to encourage pressure waves to flow through the outlet and not backward up other pipes toward other cylinders. In a set of tuned headers the pipe lengths are carefully calculated to enhance exhaust flow in a particular engine RPM range.

Header-back

Header-back (or header back) refers to the portion of the exhaust system from the outlet of the header to the final vent to open air— everything from the header back. Header-back systems are generally produced as aftermarket performance systems for cars without turbochargers.

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