FAW Exhaust System: A Critical Guide to Its 34 After-Treatment Components

Welcome to this critical technical guide on the FAW Exhaust System for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This is not just a muffler; it is a complete, multi-stage emissions after-treatment system, essential for modern diesel performance and environmental compliance.

The FAW Exhaust System is a highly engineered assembly responsible for two primary tasks: noise reduction (muffling) and emissions neutralization. This guide focuses on the ‘Selective Catalytic Reduction (SCR) After-treatment Assembly’ (1208010-90R-C00), which is the “logic box” that uses urea (DEF) to convert harmful NOx into nitrogen and water.

This in-depth guide is a vital resource for professional technicians, fleet managers, and parts specialists. We will deconstruct the entire FAW Exhaust System into its 34 serviceable components, including the main SCR unit, the inlet/outlet piping, the critical heat shields, and all the specialized mounting brackets and hardware.

Core Component: The SCR After-Treatment Assembly (1208010-90R-C00)

The heart of the modern FAW Exhaust System is the ‘Selective Catalytic Reduction After-treatment Assembly’ (1208010-90R-C00). This is the large, chassis-mounted “box” that all other components in this list support. It is not a simple muffler; it is an active chemical reactor.

This unit contains a series of catalysts. First, the hot exhaust gas passes through a **Diesel Oxidation Catalyst (DOC)**, which breaks down carbon monoxide (CO) and unburnt hydrocarbons (HC). Next, it passes through a **Diesel Particulate Filter (DPF)**, which is a ceramic “soot trap” that physically captures the black smoke particles.

After the DPF, the urea (DEF) is injected into the gas stream. This mixture then enters the **Selective Catalytic Reduction (SCR)** catalyst. Here, the ammonia in the urea reacts with the harmful Nitrogen Oxides (NOx), converting them into harmless nitrogen (N2) and water (H2O). This complex, multi-stage process is the “logic” of the FAW Exhaust System. A failure of this component will trigger a “Check Engine” light and will cause the truck to fail emissions testing.

Inlet Piping and Vibration Damping

The FAW Exhaust System is mounted to the chassis, but the engine vibrates and twists. A rigid pipe connecting the two would snap in minutes. The ‘Telescopic bellows assembly’ (1203040-2000) is the solution. This is a flexible, corrugated steel joint that absorbs the engine’s movement and thermal expansion, protecting the rest of the FAW Exhaust System from stress.

This bellows connects to the ‘Inlet pipe assembly-select catalytic reduction’ (1203815-92W), which is the main, pre-bent pipe that feeds the hot gas from the turbocharger into the SCR assembly.

This inlet pipe is heavy and must be supported, which is the job of the ‘Bracket assembly-inlet pipe’ (1203045-92W). This bracket, along with its ‘Combination bolts’ (CQ1461045) and ‘Hex nuts’ (CQ34010), holds the pipe securely to the engine or chassis, preventing it from cracking under its own weight. This entire inlet path is a critical part of the FAW Exhaust System.

The Critical Heat Shield System

The DPF “regeneration” cycle, which burns off trapped soot, can raise the temperature of the FAW Exhaust System to over 600°C (1100°F). This intense radiant heat is a major fire hazard. This parts list includes a comprehensive heat shield system to protect the truck.

This includes the ‘Heat shield assembly’ (1204045-92W and 1204025-92W), which are large, stamped-metal shields. More specifically, the SCR box is wrapped in its own set of shields:

• ‘Upper heat shield-after-treatment’ (1204038-92W)
• ‘Side heat shield-after-treatment’ (1204046-92W)
• ‘Front heat shield-after-treatment’ (1204028-76W)

These shields create a “thermal barrier” of air, reflecting the heat and protecting the chassis, fuel lines, wiring harnesses, and anything else nearby. A missing heat shield on the FAW Exhaust System is a major safety violation and will lead to melted components. These shields are secured by a ‘Bracket assembly’ (1203055-92W) and specialized ‘Hex flange bolts’ (Q1841455, Q1841450, Q1841475).

Mounting and Support Hardware

The heavy ‘SCR After-treatment Assembly’ (1208010-90R-C00) is held in place by a robust cradle system. This includes the ‘Bracket assembly-after-treatment’ (1203050-92W) and ‘Bracket assembly-after-treatment’ (1203055-92W).

These brackets are secured to the chassis, and the SCR box is then held by the ‘Clamping band assembly-after-treatment’ (1203090-73W). These bands wrap around the unit and are tensioned with bolts. To prevent metal-on-metal contact, a ‘Gasket plate assembly’ (1203025A263) is used as a vibration-damping insulator.

The rest of the FAW Exhaust System, such as the tailpipe, is hung using the ‘Clamp-muffler hanger’ (1203041-274). The entire assembly is fastened with a large array of ‘Hex flange lock nuts’ (CQ32610, Q932614), ‘Hex nuts’ (CQ34010, CQ34008, CQ34012), ‘Hex head bolts’ (CQ1501030, CQ1501025), and ‘Spring gaskets’ (Q40310, Q40308). This hardware is all high-temperature and vibration-resistant, essential for the reliability of the FAW Exhaust System.

FAW Exhaust System Parts List

The following table provides the complete, detailed breakdown of all 34 components identified in the ‘Exhaust System’ diagram for the FAW CA4251P66K24T1A3E5 tractor. This FAW Exhaust System is a complex after-treatment assembly.

Technical Specifications and Assembly Context

The specifications for the FAW Exhaust System are defined by its function as a complete, chassis-mounted emissions after-treatment system. The entire FAW Exhaust System is critical for emissions compliance and noise reduction.