Which allows exhaust gas to flow from the exhaust manifold to the intake manifold to be burned again?

• A. Turbocharger
• B. Oxygen Sensor
• C. Catalytic Converter
• D. EGR

Answer: (D)

Exhaust Gas Recirculation (EGR) reintroduces a portion of the exhaust gas from the exhaust manifold back into the intake so it mixes with incoming air and is burned again in the cylinders. This dilutes the air-fuel charge with inert gases, lowers the peak combustion temperature, and reduces nitrogen oxide (NOx) emissions. The other components don’t perform this recycling: a turbocharger uses exhaust energy to drive a turbine and boost intake air, an oxygen sensor only monitors the oxygen content in the exhaust, and a catalytic converter treats pollutants after combustion without sending exhaust back into the intake. So, the mechanism that allows exhaust gas to flow back into the intake to be burned again is Exhaust Gas Recirculation.