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What is the air pump in a car engine?

Published in Automotive Emissions System 2 mins read

In a car engine's emissions control system, the air pump is a specific component designed to supply air to the exhaust stream.

This device, officially known as the AIR pump (secondary air injection), is a vane pump. Colloquially, it's often referred to as the "smog pump."

Role of the Air Pump

The air pump is a key part of pumped air injection systems. Its primary function is to force fresh air into the exhaust gases, typically near the engine's exhaust ports or into the catalytic converter. This additional oxygen helps to burn off uncombusted or partially combusted fuel remaining in the exhaust, thus reducing harmful emissions like carbon monoxide (CO) and hydrocarbons (HC).

How the Air Pump Works

Based on the provided information:

  • It is a vane pump.
  • It is turned by the engine. This can be done via a belt connected to the engine's crankshaft pulley (like many other accessories) or powered by an electric motor.
  • Its air intake needs to be clean. The air is filtered to prevent dirt particles from damaging the pump or the downstream system. This filtering is done by a rotating screen or by using the vehicle's main air filter.

Here's a simple breakdown:

Feature Description
Component Type Vane pump
Official Name AIR pump (Secondary Air Injection pump)
Common Name "Smog pump"
Power Source Engine belt or electric motor
Air Intake Filtered by rotating screen or vehicle air filter
Purpose Supplies air to exhaust stream for emissions control (to burn off pollutants)

Importance in Emissions Control

The air pump plays a vital role, especially during cold starts. When an engine is cold, the catalytic converter hasn't reached its optimal operating temperature yet. Injecting fresh air helps to raise the temperature of the exhaust gases and the catalyst more quickly, allowing the converter to become effective sooner and reduce cold-start emissions significantly.

While common on older vehicles, modern vehicles often integrate secondary air injection differently or rely more heavily on advanced catalytic converters and engine management systems. However, where fitted, the AIR pump is a critical component for meeting emissions standards.