Centersection: The housing between the exhaust and intake sides of the turbo that houses the turbo shaft and contains the bearings, oiling system, and water-cooling system.
Charge air cooler: A radiator placed between the turbo compressor outlet and the engine intake manifold used to cool the intake charge, which is heated by the compression of the turbo (also called an intercooler or aftercooler).
Choke line: The boundary on the righthand side of a compressor map that indicates the rpm where the turbo efficiency quickly drops. If this happens at low rpm, a larger turbo is needed.
Compound turbos: Two or more turbos that feed into each other in series to build high boost pressures. The new 6.4L Power Stroke in the '08 Super Duty uses a small variable-geometry turbo that pumps into a larger turbo to create stock boost levels of 20 psi at low rpm and 40 psi when the engine is under a full load.
Compressor map: A graph that diagrams the performance of a turbo by showing turbo speed, efficiency, flow rate, and boost pressure. The left border represents the surge line, the right side shows the choke line, and the patterns in between are efficiency islands.
Compressor wheel: The fan blades that suck in the intake air and compress it against the compressor housing and backplate.
Cool down: Running the engine until the exhaust temperature is low (less than 300 degrees F) so oil in the centersection doesn't cook when the engine is shut down and the oil flow stops.
Crossover pipe: A tube leading from the exhaust manifold to the turbine inlet. V-6 and V-8 engines use a crossover pipe, but the inline-six Cummins exhaust manifold feeds directly into the turbo.
Divided turbine inlet: A split inside the exhaust manifold and turbine housing that separates exhaust output from cylinders to prevent turbulence based on the firing order.
Dr. Alfred Buchi: Inventor of the turbocharger in 1909. He proposed the first turbodiesel engine in 1915.
Downpipe: The exhaust pipe that leads from the turbine outlet to the exhaust system under the vehicle.
Efficiency islands: Areas on a compressor map that indicate the operating conditions under which peak efficiency occurs.
EGR: Exhaust-gas recirculation routes some exhaust gas back into the intake manifold after it passes through a water-cooled heat exchanger. EGR reduces emissions of nitrogen oxides.
EGT: Exhaust-gas temperature that should be monitored to prevent the turbo from overheating, which can lead to failure (1,250 degrees F maximum for extended periods).
Exducer: Where flow exits the turbine or compressor wheel.
Exhaust manifold: A cast-iron collector on the engine head(s) that routes exhaust gases to the turbo, EGR system, and crossover pipes (V-6 and V-8).
External wastgate: A wastegate that is not built in to the turbo.
Headers: Tubular steel sections used in place of exhaust manifolds for maximum flow efficiency. Rarely used in diesel applications.
Heat soak: When heat from the turbine housing is transferred to the compressor side of the turbo. Water-cooled turbos help prevent this, along with keeping the lubricating oil cooler.
Impeller: Another name for a compressor wheel.
Inducer: Where flow enters the turbine or compressor wheel.
Intake manifold: Routes airflow from the intercooler line into the intake ports in the head(s) of the engine.
Intercooler: Air-to-air or air-to-water radiators used between the turbo and the intake manifold to reduce intake temperature, which is heated by the pressurization inside the turbo (also called aftercharger or charge air cooler).
Internal wastegate: A built-in valve that diverts exhaust gases away from the turbine when a certain boost level is reached on the compressor side of the turbo. Can be mechanically or electrically controlled.