Turbocharger Central Housing (CHRA)

The central housing, or CHRA (Center Housing Rotating Assembly), is the core part of a turbocharger, connecting the turbine and compressor sides and ensuring their smooth operation. This component houses the most important mechanisms of the turbocharger – the central shaft, bearings, oil supply system, and cooling channels. The CHRA design allows the turbocharger to rotate at extremely high speeds (up to 300,000 RPM), and its longevity depends on quality manufacturing, materials, and proper operation.

CHRA Construction – How Is It Made?

The CHRA is the main module of the turbocharger, where all the most important parts of the turbine and compressor come together. The main components are:

Central shaft (Shaft & Wheel Assembly) – connects the turbine wheel to the compressor wheel and transfers mechanical energy. Made from heat-resistant alloys (e.g., Inconel), as it must withstand extreme temperatures and mechanical loads.
Bearings – can be of two types:
- Journal Bearings – most commonly used due to their simple design and reliability.
- Ball Bearings – lower friction, allowing for faster turbo response and longer service life.
Oil supply and return channels – essential for providing adequate lubrication and cooling to the turbo. Insufficient oil supply can cause rapid wear of bearings and the shaft.
Cooling system – the CHRA can be oil-cooled or water-cooled (water-cooled CHRA). Water-cooled models regulate temperature more effectively and help reduce thermal stress.
Seals and piston rings – prevent oil from entering the intake or exhaust system.

CHRA Functions – Why Is It So Important?

The CHRA is the heart of the turbocharger, as without it, the turbocharger could not function properly. The main functions of the CHRA are:

Energy transfer: The CHRA allows the turbine wheel to transfer kinetic energy to the compressor wheel, which compresses the air.
Bearing lubrication: Oil circulation ensures low friction and reduces mechanical wear.
Cooling: Proper cooling protects the CHRA from overheating and material deformation.
Oil sealing: Ensures that oil does not enter the intake or exhaust system, which could cause engine problems.

Bearing Technology – Ball Bearings or Journal Bearings?

One of the most important components of the CHRA is the bearings, which ensure smooth turbo operation. There are two main types of bearings:

Journal Bearings

These are traditional turbocharger bearings that rely on an oil film to reduce friction. They are cheaper but have a slower response time compared to ball bearings.

Ball Bearings

Used in high-quality turbochargers, as they reduce friction and help achieve boost pressure faster. Such bearings are used by manufacturers like Garrett, BorgWarner, and Mitsubishi Turbo.

CHRA Failures and Their Causes

CHRA failures can lead to serious turbocharger damage and reduced engine performance. The most common failures are:

Oil starvation: Insufficient lubrication can cause bearing and shaft wear.
Oil leakage: Damaged seals can allow oil to enter the intake or exhaust system.
Bearing wear: Can cause whistling, vibration, and even shaft failure.
Overheating: Due to an inadequate cooling system, the CHRA can deform.

CHRA Price and Manufacturers

CHRA module prices depend on the manufacturer and the technologies used. Here are some examples of market prices:

Standard CHRA (journal bearings): 150–500 EUR.
Ball bearing CHRA: 500–1500 EUR.
High-performance CHRA (Performance Turbo CHRA): 1000–3000 EUR.

The most well-known CHRA manufacturers are Garrett, BorgWarner, Mitsubishi Turbo, Holset, and IHI Turbo. They supply high-quality modules used in both production and racing engines.

Why Is the CHRA the Most Important Part of a Turbocharger?

The central housing (CHRA) is the core component of a turbocharger, responsible for energy transfer, lubrication, and cooling. High-quality CHRA ensures long-lasting turbo operation, reduces potential failures, and helps maintain optimal engine power. If you aim for maximum reliability and efficiency, it is worth choosing CHRA modules from reputable manufacturers and regularly maintaining the oil system to ensure the turbocharger operates efficiently for a long time.