Definition
A turbocharger is a radial fan pump driven by the energy of the exhaust gases of an engine. Turbochargers consist of a turbine and a compressor on a shared shaft. The turbine is a heat engine in itself. It converts the heat energy from the exhaust to power, which then drives the compressor, compressing ambient air and delivering it to the air intake manifold of the engine at higher pressure, resulting in a greater mass of air entering each cylinder.
Objective & Benefits
The objective of a turbocharger is to improve upon the size-to-output efficiency of an engine by solving one of its cardinal limitations. A naturally aspirated automobile engine uses only the downward stroke of a piston to create an area of low pressure in order to draw air into the cylinder through the intake valves. This ability to fill the cylinder with air is its volumetric efficiency. Because the turbocharger increases the pressure at the point where air is entering the cylinder, a greater mass of air (oxygen) will be forced in as the inlet manifold pressure increases. The additional oxygen makes it possible to add more fuel, increasing the power and torque output of the engine while reducing emissions.
A typical turbocharger assembly consists of the components shown in the following. There are many variations of this assembly with minor differences. Some turbocharger assemblies will contain supplementary components such as a ball bearing cartridge, a variable nozzle turbine (VNT) assembly, or a wastegate. If you encounter questions regarding any of these supplementary components please contact SPELAB for technical assistance.
Turbochargers are designed to last for the service life of the engine. When a turbocharger fails, it is important to look past obvious damage to locate and fix the root cause of the failure. In most cases, the cause of turbocharger failure originates from an installation error, improper vehicle systems, or improper operation of the vehicle, details about which are listed below.
LACK OF LUBE / CONTAMINATED OILOften caused by issues related to:
- Low engine oil pressure/level
- Obstructed oil supply/drain line
- Improper weight of oil
- Fast starts in cold weather
- Hot shutdown (engine shut off at high rpm)
- Engine blow-by
FOREIGN BODY IN EXHAUST / AIR INLET
Often caused by foreign particles entering the turbine or compressor stages during or after installation, such as:
- Screws or nuts
- Sand or dirt
- Metal powder or shavings
- Pieces of broken air filters
- Compressor wheel lock nut
HIGH EXHAUST TEMPERATURE
Often caused by issues related to:
- Incorrect fuel ratio (high fuel setting)
- Insufficient air supply (caused by a plugged air cleaner, etc.)
- A leak in the in the intake manifold or piping
- Excessive exhaust restrictions
- Plugged aftercooler core
DEFECTIVE WORKMANSHIP / MATERIAL
While rare, the visible evidence is often easy to recognize. Causes include:
- Compressor wheel lock nut failure (nut is missing & there is damage to the vanes)
- One-sided wear on the compressor housing
- Back plate bolt is loosened and contacted the back of compressor wheel
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