Audi RS4 B8 4.2 FSI CFSA Air Filter Housing Box Assembly 8T0133835B

Audi RS4 B8 4.2 FSI CFSA Air Filter Housing Box Assembly is a factory intake system component, designed specifically for the high-performance gasoline engine. Thanks to its precise fitment within the engine bay, it ensures stable mounting of the filter element, thereby providing consistent airflow and predictable operating conditions for the powertrain. This solution is intended for users who expect original intake geometry and compatibility with factory Audi components.

Specifications and technical data

• SKU: 8T0133835B
• Mark: Audi
• Condition: Used
• OEM Part Number: 8T0133835B
• Substitutable numbers: 8T0133835B, 8T0 133 835 B
• Fuel type: Petrol
• Category: Air Filter Housings

Purpose and function in the intake system

The air filter housing in the Audi RS4 B8 4.2 FSI CFSA is responsible for the airtight routing of air from the intake to the filter element and further towards the throttle body. A properly selected housing:

• maintains a stable position of the air filter within the tolerances required by the manufacturer,
• reduces turbulence and uncontrolled flow resistance,
• protects the filter element from contaminants in the engine bay,
• works in harmony with stock intake ducts and gasoline engine accessories.

As a result, the intake system maintains the parameters intended for the 4.2 FSI unit, which promotes repeatable performance and stable operation at high RPMs.

Benefits of using the original air filter housing

Using the factory air filter housing in the RS4 B8 is important for both engine durability and operational comfort. Key advantages include:

• Compatibility with the stock intake system – no need for modifications to mounts, hoses, or sensors.
• Properly selected volume and shape of the filter chamber, supporting the characteristics of a high-power gasoline unit.
• Ability to maintain factory intake acoustic parameters, without unwanted resonances.
• Easy service access to the filter element during periodic maintenance.

For sports-oriented vehicles like the RS4 B8, maintaining the original intake design is essential for preserving predictable engine behavior across the full load range.

Component condition and service application

The presented air filter housing is a pre-owned part, which allows for an economical replacement of a damaged or incomplete housing while maintaining factory specifications. This type of part is particularly useful in situations where:

• the original housing has cracked or deformed,
• mounts were damaged during previous repairs,
• it is necessary to revert from aftermarket tuning solutions to the stock intake system.

For workshops specializing in the Audi brand and users servicing their vehicles themselves, this is a practical solution that allows for restoring correct intake geometry without interfering with other components.

Application in gasoline vehicles

The housing was designed to work with the gasoline engine, which means it is matched to the airflow characteristics typical of FSI units. In practice, this translates into:

• stable air supply conditions at high engine speeds,
• preservation of factory engine control unit maps,
• consistency with stock solutions regarding heat dissipation from the engine bay.

Thanks to this, the housing supports trouble-free vehicle operation in daily use as well as during dynamic driving.

Related Audi intake system components

If you are planning a comprehensive repair or upgrade of the engine area in your Audi and need other components from the same group, such as intake ducts, air supply hoses, or additional mounting hardware, check out the available parts in the Audi Air Filter Housings category.

When planning broader service work, it is also worth checking out practical tips regarding the safe selection of used components – you will find them in the article "Second-hand braking system: how to safely choose discs, calipers, and ABS?", which discusses universal principles for assessing the condition of aftermarket parts.