Chapter 29-Fixed Geometry and Wastegated Turbochargers

compressor wheel

a centrifugal-type air pump attached to the turbine wheel. The compressor wheel uses centrifugal force to compress air

turbo lag

a delay between driver demand for power and the point when the engine responds with power proportional to driver demand

single sequential turbocharger (SST)

a turbocharger design that uses a single turbine wheel and two compressor wheels. Together the compressor wheels supply a greater volume of air to the intake manifold

variable geometry turbocharger (VGT)

a turbocharger with the capability of changing boost pressure independent of engine speed and load; also known as the variable nozzle turbocharger (VNT) and variable vane turbocharger (VVT).

asymmetrical turbocharger

a turbocharger with volutes of two different sizes. Asymmetrical turbochargers are used by Detroit DD series engines

fixed geometry turbocharger

a turbocharger without boost pressure controls; the name is derived from the fact the housing and components have unchanged dimensions

supercharger

an engine that pressurizes the air intake system above atmospheric pressure

naturally aspirated

an engine that uses only atmospheric pressure and not pressurized air to charge the cylinders with air

wastegate

an exhaust bypass valve in the turbine housing that allows exhaust gases to bypass the turbine and directly enter the exhaust pipe, thus "wasting" some of the exhaust energy.

transient emissions

emissions produced temporarily when the engine load or speed is increased, such as when accelerating or upshifting gears

boost pressure normalization

the feature of a turbocharger that maintains boost pressure even as the engine climbs to higher altitudes with low air density

compressor housing

the housing that encloses the compressor wheel

A/R ratio

the ratio between the area (A) of either the compressor or turbine inlets to the radius (R) of the housing

parallel turbocharger

the use of two turbochargers that share the exhaust energy from an engines from an engine's exhaust manifold. The output of both turbochargers is connected directly to the intake manifold of the engine to increase airflow into the engine

series turbocharging

using two differently sized turbochargers where the compressor outlet is connected to the inlet of a second compressor