FAW Floor Insulation Underlay: The 6 Essential Pieces for a Flawless Cab Interior Unveiled

Welcome to this in-depth analysis of the FAW Floor Insulation Underlay. This is the complete, multi-piece, pre-molded floor covering system for the FAW Jiefang CA4251P66K24T1A3E5 6×4 diesel semi-trailer tractor. This assembly is the *final* layer of the cab’s interior, serving as the primary “logic” for driver comfort, acoustic absorption, and long-term durability.

The FAW Floor Insulation Underlay is not the same as the ‘Soundproofing and Heat Insulation Pad’ (Assembly 623). That pad is the first-layer barrier *against* noise and heat. This underlay is the “comfort layer” that sits on top. Its “logic” is to provide a durable, non-slip, fire-retardant, and easy-to-clean wear surface. It also functions as a final acoustic *absorber*, reducing in-cab echo and high-frequency noise.

This expert guide is essential for cab technicians, parts specialists, and fleet managers. We will deconstruct the entire FAW Floor Insulation Underlay system into its 6 key component types. We will analyze the “4-piece” modular logic (Left, Right, Middle, Rear) and the robust “32-point” fastening system that secures it to the cab floor.

The “Comfort Layer” Logic of the Underlay (The “Longer” Module)

The FAW Floor Insulation Underlay is a multi-functional system. Its design “logic” is to provide the final, crucial interface between the driver and the cab’s metal structure, focusing on durability, acoustics, and safety.

1. Acoustic Absorption Logic (NVH):

This is a key function. The assembly *below* this one (the ‘Soundproofing Pad 623’) is a “sound barrier,” designed to *block* low-frequency engine noise from entering. This FAW Floor Insulation Underlay serves a different purpose: “sound absorption.”

The material is either a tufted, high-density carpet or a mass-backed vinyl. Both materials are “acoustically dead.” Their “logic” is to absorb *in-cab* sound waves, such as the radio, conversation, and high-frequency wind noise. This prevents sound from reflecting off the hard floor pan, which would create a loud, fatiguing “echo chamber” effect. This absorption logic is critical for driver comfort and for the clarity of phone calls and navigation commands.

2. Durability & Safety Logic (The Wear Surface):

This is the primary “wear surface” for the entire cab. The “logic” of its material science is toughness. It is designed to withstand decades of abuse from:

• Abrasion: Constant friction from heavy, muddy, and gravel-encrusted work boots.
• Chemicals: Spills of diesel, oil, coffee, and cleaning solutions. The material is chemically inert and easy to clean.
• Moisture: Rain and snow tracked in by the driver. The material is non-porous and designed to prevent moisture from seeping into the insulation pad below, which would cause mold and rust.

The “safety logic” is twofold. First, the surface is textured (pebble-grain vinyl or tufted carpet) to be non-slip, even when wet. Second, the entire FAW Floor Insulation Underlay is treated with fire-retardant chemicals to meet strict FMVSS 302 (Federal Motor Vehicle Safety Standard) anti-flammability regulations, a critical safety feature.

Core 2: Deconstructing the 4-Piece Modular Logic (MSUs 1-4)

The FAW Floor Insulation Underlay is not a single piece of carpet. It is a kit of four distinct, 3D-molded MSUs. This “modular logic” is essential for both manufacturing and serviceability.

MSU 1 & 2: ‘Left Part’ (5109311-A01) & ‘Right Part’ (5109312-A01): These are the two main floor sections. They are complex, 3D-molded shapes that perfectly contour the driver and passenger footwells, rising up to meet the firewall and wrapping around the transmission tunnel.

MSU 3: ‘Middle Part’ (5109313-A01): This component is the “cap” for the transmission tunnel. It bridges the gap between the left and right footwell pieces, creating a seamless look.

MSU 4: ‘Rear Part’ (5109316-D03): This is the large, flat piece that covers the cab floor *behind* the seats. It runs from the back of the seat mounts to the rear cab wall, completing the floor covering.

The service “logic” of this 4-piece design is a major cost-saver. If a specific area is damaged (e.g., a tool is dropped, puncturing the right footwell, or a fluid spill contaminates the rear section), the fleet manager does not need to buy an entire new cab floor. They simply order the one affected MSU (e.g., ‘5109312-A01’), saving time and money.

Core 3: The 32-Point Fastening System “Logic” (MSUs 5 & 6)

The final components of the FAW Floor Insulation Underlay reveal its high-quality, heavy-duty “logic.” This underlay is not simply “laid in” or held by trim. It is mechanically fastened to the cab floor by a 32-point system.

This system consists of thirty-two (32) ‘Gaskets’ (5109318-A01) and thirty-two (32) ‘Hexagon nuts’ (CQ34006).

Fastening Logic: This implies that the cab floor pan is pre-studded with 32 fixed, welded studs that poke up through the ‘Soundproofing Pad’ (623) and then through pre-cut holes in this FAW Floor Insulation Underlay.

MSU 5: ‘Gasket-floor insulation underlay’ (5109318-A01): This is the first part of the “logic.” This component is a large-diameter washer or “gasket.” Its function is critical: it prevents the metal nut from pulling *through* the soft, tufted carpet or vinyl of the underlay. It distributes the clamping force, ensuring a secure fit without tearing the material.

MSU 6: ‘Hexagon nut’ (CQ34006): This is the clamping fastener. The “logic” of using 32 of them is to make the underlay a semi-permanent, structural part of the floor. This robust system ensures two things:

• Safety: The mat can *never* slip or “bunch up” under the accelerator or brake pedals.
• Sealing: It pulls the underlay *tightly* against the floor pad beneath it, creating a perfect seal that prevents water, dirt, and noise from creeping under the edges.

FAW Floor Insulation Underlay Parts List

The following table provides the complete, detailed breakdown of all 6 component types identified in the FAW Floor Insulation Underlay assembly for the FAW CA4251P66K24T1A3E5 tractor.

Technical Specifications and Assembly Context

The specifications for the FAW Floor Insulation Underlay are defined by its function as the primary wear-surface and acoustic absorption layer for the cab interior.