STEYR MOTORS Marine Engine 2012 Series, Service Manual

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Fuel System
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03.00.06 Schema – Variable Geometry Turbochargers
Function turbo charging system
Turbocharger consists of two fundamental components, a turbine and a compressor.
The function of the turbine is to scavenge waste exhaust heat and translate it into
rotational motion. This rotational motion is then used to drive the compressor, which
compresses air for the consumption of the engine. The purpose behind the
turbocharger is to overcome the fundamental drawback of the internal combustion
engine, its volumetric efficiency limit. An engine drawing air in from the atmosphere
can only achieve a volumetric efficiency of up to 100%, meaning that the pressure
inside an individual cylinder is equal to atmospheric pressure while the intake cycle is
occurring. Since the amount of power that can be extracted from an engine is
proportional to the fuel it burns, and the fuel consumption is limited by the amount of
air present in a cylinder, times the number of cylinders (the so-called "displacement"),
the volumetric efficiency limit effectively constrains the power of the engine. The
turbocharger provides an alternative means of extracting more power from a given
displacement by increasing the volumetric efficiency to points significantly above its
volumetric design. The pressure in the cylinders is greater than atmospheric, thanks
to the compressor on the turbocharger.