For diesel engines Issues Explained: A Complete Breakdown

How it Works: For diesel engines

The diesel exhaust system channels combustion by-products from the cylinder head to the atmosphere while sequentially harvesting energy and transforming pollutants into harmless constituents. High-energy gas pulses exit each port and merge inside a cast manifold that directs flow toward a turbocharger turbine, recovering kinetic energy to boost intake pressure. Downstream, a robust stainless downpipe conveys gases to a diesel oxidation catalyst (DOC). Platinum and palladium surfaces within the DOC oxidize unburned hydrocarbons and carbon monoxide while converting nitric oxide to nitrogen dioxide, raising temperature for subsequent stages. Conditioned gas next enters a diesel particulate filter (DPF), a cordierite or silicon-carbide wall-flow brick that traps soot on porous channel walls; periodic ECU-controlled post-injection events elevate exhaust heat, regenerating the filter by oxidizing stored carbon. A doser then meters aqueous urea (DEF) into the hot stream, where it hydrolyzes to ammonia before reaching the selective catalytic reduction (SCR) catalyst. Vanadia, copper, or iron zeolite sites promote reduction of nitrogen oxides into elemental nitrogen and water. An ammonia slip catalyst polishes residual NH₃. Temperature, differential-pressure, and NOx sensors positioned before and after each module supply feedback, enabling the control unit to regulate injection, regeneration, and turbo boost precisely. Finally, resonators and a muffler attenuate pressure waves, ejecting compliant, low-noise exhaust through the tailpipe, ensuring diesel, hybrid, and renewable-fuel powertrains meet stringent global emission targets. This design maintains proper back-pressure and catalyst durability.