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How we remanufacture a turbocharger bearing assembly (CHRA)? - AutoNorma

How we remanufacture Centre Housing Rotating Assembly (CHRA) on our turbochargers?

Turbocharger is used to supercharge internal combustion engine's power output by forcing extra compressed air into the combustion chamber. It helps to ensure higher power and torque of the diesel or petrol engine. It consists of two main parts, a blower and a turbine housing, which are interconnected by a bearing node. If the bearing assembly or other parts of the turbocharger are damaged while driving, be sure not to continue operating your vehicle. Doing so can make for a substantially more expensive repair.

The bearing unit of the turbocharger, or CHRA (center housing rotating assembly), consists of a bearing, a bearing bed, a bearing center with oil chambers or water cooling chambers, a turbine shaft, and turbine propellers on the suction and exhaust side. Properly assembled refurbished bearing center works reliably and for a long time at high speeds, all while maintaining the proper lubricating function of the oil as a mediator of the rotational movement of the shaft inside the bearing.

Most common causes of damage to centre housing rotating assembly (CHRA)

  • natural wear and tear due to substantial vehicle usage (approximately 200 - 250 thousand km)

  • mechanical damage (intrusion of foreign object, insufficient oils levels, oil contamination and its sediment, snapping of the cast iron bearing, corrosion)

  • shortage in the lubricating function of mediator (jamming of the turbine shaft)

  • clearance in radial bearing

The symptoms of damaged centre house radial bearing 

  • shortage in engine power, the car does not "pull"

  • engine shuts off and won't start again

  • engine whistling

Engine whistle accompanied by a drop in power may indicate a foreign object entering the air intake or exhaust inlet into the turbocharger compartment. It is the penetration of a foreign body that disrupts the optimal state of the rotary assembly.

In modern turbochargers, the ingress of a foreign body not only deforms the turbine wheel, but also damages the swivel blades. Secondly, the regulation in the vacuum or electromechanical design can also be damaged.

Remanufacturing of centre housing rotating assembly (CHRA)

  1. Disassembly of the CHRA into its various components

  2. Removal of damaged components

  3. Cleaning, power-washing, and sand-blasting of intact components

  4. Reassembly of the CHRA from brand-new as well as those previously cleaned components

  5. Dynamic balancing + calibrating = testing protocol

  6. Packing and dispatching to the customer

In the event of a failure of any part of the turbocharger, we always recommend a complete overhaul. The individual components have a similar lifespan, and it is likely that if one of them breaks down, another will soon follow. Once you have the turbo removed from the car, a complete overhaul will ensure that you will not dismantle it again in the foreseeable future in case of another defect. Unfortunately, although the turbo may seem fine at first glance until it is disassembled, it is not possible to predict how it is doing and how long it will still function.

For a step-by-step description of complete turbocharger remanufacturing, click here

If the turbocharger bearing assembly (CHRA) is damaged, usually it must be replaced with a brand new, completely assembled and thoroughly balanced unit directly from the manufacturer. In such a case, we only transport the knot as a control in order to exclude possible damage during transport or imperfections from production. Disassembled parts of the bearing housing, which are not damaged or too corroded, are sandblasted and ultrasonically cleaned. If they do not show signs of wear (especially in the area of ​​the piston ring on the turbine chamber side) and if they have the original dimensions, we fit them with new bearings, a blower chimney, a turbine wheel with a shaft, and a cover plate.

The complete center of the blower assembled in this way is then balanced and tested for oil leakage on the compressor side and on the blower side. If the knot complies at all points, it can be used as a full-fledged replacement for a new piece.

Balancing the center of the blower is one of the most important steps that has an immediate effect on its life and bearing wear during operation. Usually, we balance all blowers by 20-40,000 rpm. above the limit prescribed by the manufacturer and we always try to reduce the vibration coefficient to almost zero, i.e. to a significantly lower value than tolerated by the manufacturer. We perform all balancing on a balancing bench, which is annually revised and tested by the manufacturer.

Proper diagnostics of the problem is the key!

This has been remanufacturing of centre housing rotating assembly (CHRA) in a few basic steps. Complete turbocharger remanufacturing, however, is in reality a much more complex process. When deciding to whom to entrust the refurbishment of a bearing unit or a whole turbocharger, focus on the experience of a particular company and its diagnostic background. Precisely due to poor diagnosis of the problem, unnecessary overhauls often occur when the turbocharger shows signs of wear, but its replacement or overhaul will not solve the problem with the operation of the vehicle.