Turbochargers

Turbocharger - genesis and application.

Since their invention, turbochargers have changed the face of automitive industry. Initially used mainly in aviation, they quickly found their way into passenger cars, trucks and the marine and aerospace industries. Thanks to their ability to increase engine power while reducing exhaust emissions, they have become an integral part of many modern vehicles. Initially, turbochargers faced some problems, such as a delay in response to changes in engine load (known as turbo lag) and higher lubrication and cooling requirements. However, thanks to advances in technology and the introduction of advanced control systems, these problems have largely been solved. Sufficiently fast and precise regulation of boost pressure, and thus harmonious development of engine power and high torque values, is possible thanks to the introduction of variable turbine geometry, electronic actuators and Twin Turbo designs, i.e. sequential charging.

Construction and principle of operation.

The exhaust gases leaving the engine cylinders are directed through the exhaust manifold into the turbine housing. Flowing through the turbine blades located there, they set the turbocharger rotor in motion and then escape freely into the engine's exhaust system. At the other end of the shaft is the compressor, in which the rotating compressor wheel (compression wheel) draws in air, compresses it to a pressure higher than atmospheric pressure and directs it further through the intake pipes to the engine cylinders. The control system, a wastegate or variable turbine geometry (VNT/VGT/VTG), is responsible for adjusting and maintaining the correct pressure. The rotating system is supported in the turbocharger's bearing housing by plain bearings (less commonly ball bearings): main and axial (thrust). The engine oil is continuously supplied under pressure to the turbocharger's bearing housing (core/CHRA), flows through the bearing arrangement of the rotating system and then flows freely back to the engine. Some turbocharger models have additional channels in the bearing housing through which the coolant flows - this is to improve the cooling of the turbocharger core and reduce the risk of oil sintering inside.

Construction of the turbocharger:

1. Turbine housing (so-called hot side)
2. Impeller with turbine wheel
3. Bearing housing (core/CHRA)
4. Bearings - main and axial bearing(s)
5. Sealing rings and other seals
6. Compressor housing (so-colled cold side)
7. Compressor wheel (compression wheel)
8. Charge pressure control system (wastegate or variable geometry)
9. Boost pressure actuator (pressure/vacuum valve or electronic adjuster)
10. Compressed air bypass valve (petrol engine turbochargers only)

Turbocharger remanufacturing process.

The remanufacturing process consists of several main stages:

1. Initial condition assessment - mainly assessing the presence and location of oil leaks, visible mechanical damage, assessing the operation of the boost pressure control system, the efficiency of the valve/valves and electronic adjusters. 
2. Disassembling the turbocharger into its component parts - allows access to the individual parts of the turbocharger and a thorough assessment of all its components.
3. Cleaning of components - sometimes only after thorough cleaning is it possible to verify them precisely. Some components will be reused after cleaning in the reconditioning process (provided they are not damaged).
4. Completion of new components - parts to replace damaged ones or those that are always being replaced (bearings, seals, etc).
5. Thorough test of the valve/pressure regulator or electronic adjuster - at this stage, the position sensor of the variable geometry system or wastegate valve is replaced (if present and damaged) and the electronic adjuster of the wastegate/variable geometry valve is repaired (if damaged).
6. Low-speed balancing of a turbocharger rotor - the first of two stages of balancing a turbocharger rotating system, consisting in correcting the "play" of the rotor during operation. The measurements are performed on a high-quality Schenck balancing machine.
7. Assembling the turbocharger core - the complete rotating system including new bearings and seals is assembled in the turbocharger centre body (core/CHRA).
8. High-speed balancing of the rotating system - exact measurement and correction of the balance of the complete rotating system operating in the bearings at speeds of up to 200,000 rpm. Over the course of several measuring cycles, the unbalance is corrected to an appropriate value, often lower than with brand-new turbochargers. During this operation, the turbocharger operates under similar conditions to an internal combustion engine - the rotating system reaches speeds of the order of 200,000 rpm, and engine oil is continuously supplied to its bearings at the appropriate pressure (which also makes it possible to verify the tightness of the turbocharger's lubrication system). The high-speed balancing process is carried out on high-quality Schenck balancing machines.
9. Pre-assembly of the turbocharger and setting/calibration of the boost pressure control system - precise adjustment of the operating range of the wastegate or variable geometry system.
10. Final assembly of the turbocharger and final quality control in accordance with ISO 9001:2015.

Causes and types of damage.

With our specialists, you can be sure that turbocharger remanufacturing is carried out in a comprehensive and professional manner. Our aim is not only to remove the fault, but also to understand and provide the customer with information on the possible causes. We believe that such an approach will avoid similar problems in the future, which is why we always strive to act transparently and with full commitment.

Symptoms that may indicate a defective turbocharger:

1. Deterioration of engine performance (often referred to as "lack of engine power")
2. Noise - whistling, humming
3. Grey/blue/black smoke coming from the exhaust pipe
4. Turbocharger oil leaks, increased engine oil loss

The most common turbocharger failures are:

1. Oil leaks into the engine's intake and/or exhaust system are usually caused by damage or worned out of the turbocharger's sealing rings or increased rotor clearance. However, it should be noted that oil leaks can also affect a fully operational turbocharger that does not have the right operating conditions (first of all, the free oil return from the turbocharger to the engine is disturbed).
2. Mechanical damage to the compressor and/or turbine blades caused mainly by foreign objects in the engine intake or exhaust system.
3. Increased radial and/or axial rotor play (in extreme cases a broken shaft) usually resulting from contamination of the engine oil or lack of lubrication of the rotating system.
4. Defects in the boost pressure control system - untight or blocked pressure/vacuum valve, damaged turbo copy sensor (wastegate or variable geometry valve position sensor), electronic adjuster. Too much carbon build-up can block or limit the operating range of the turbo variable geometry system.
5. Cracks in the turbine housing (including the engine exhaust manifold if integrated with it). This is common in turbochargers operating in petrol engines due to the higher exhaust gas temperature compared to a diesel engine.