A turbocharger is an exhaust-driven air compressor. It becomes an air compressor by utilizing expanded exhaust gases from the engine. The exhaust gas pressure and the heat energy extracted from the gas causes the turbine wheel to rotate, thus driving the compressor wheel through a common shaft. Exhaust temperature and pressure drop as exhaust passes through the turbine housing and into the exhaust system. The rotating compressor wheel draws air in and the blades accelerate and expel the air into the compressor housing. Once into the compressor housing, the air is compressed and flows toward the intake manifold, pressurizing the intake in a measurable form we call boost pressure.
A turbocharger is designed to provide peak boost for the engine under maximum power at high RPM. Because of this, a turbo is less efficient at providing boost at lower RPM and in the torque range. In order to improve boost at the lower RPM, smaller wastegated turbine housing is put on the turbo to allow the boost to build sooner in the RPM range. To prevent over boosting, a wastegate actuator opens as the boost reaches maximum pressure for that engine and “dumps” the exhaust gas before it spins the turbine wheel any faster.
Yes. However, seals in a turbocharger are usually a piston ring style. These piston rings rely on close tolerances; for instance, when tolerances are excessive due to worn ring grooves, bearings, thrust washers, etc. Just replacing the seals will not fix a leak. Oregon Fuel Injection stocks many turbo assemblies, rebuilt and new, on the shelf for reduced downtime.
Before you replace the turbocharger on your engine because of low power, check the following items with the engine shut off:
Wheel and shaft are loose side to side: This is normal, because with oil pressure to the turbocharger, the shaft (and bearings) floats on a film of oil. If the compressor wheel or turbine wheel is in contact with the housing, then the turbocharger needs to be replaced.
The shaft and wheel assembly spin freely: If it is stiff to turn, replace the turbocharger.
Check the air filter: If plugged, replace it because the engine will not get enough air.
Exhaust manifold (or “feed” piping to the turbocharger): If exhaust gases are leaking, then the turbocharger will not spin “up” to full speed, causing low boost.
See more specific information on this blog post
Lack of lubricant can cause high-speed bearings to fail. Bearing failures can lead to rotational instability damaging seals and allowing the wheels to rub against the housing. If continued, this condition can lead to turbocharger failure.
Foreign objects can damage the high-speed turbine and compressor wheel blades, causing wheel imbalance and unstable rotation. This puts an additional load on bearings that leads to bearing failure and eventually turbo failure.
Contaminated lubricants can score shaft journals and bearings, block oil passages and wear out seals, resulting in heavy leakage. Continued operations under these conditions can result in bearing failure. Turbos typically spin 50 times faster, up to 300,000 rpm, than the engine rpm.
Turbocharger failure can be prevented with careful installation, proper operation and a sound preventative maintenance program.
At LOW SPEEDS, the vanes (or nozzle ring) close, which: Restricts exhaust airflow through the turbine, increases turbine power, and increases boost pressure.
At HIGH SPEEDS, the vanes (or nozzle ring) open, which: Maximizes exhaust gas flow, avoids turbo over-speed, and maintains required boost pressure.
VGT turbos take the advantages of a waste gated turbocharger one step further, for improved acceleration and reduced emissions.