Engine Specific Weight and Specific Volume

2.11 Engine specific weight and specific volume

Engine weight and bulk volume for a given rated power are important in many applications.Two parameters useful for comparing these attributes from one engine to another are:

                                engine weight
Specific weight = -----------------------------------
                                 rated power

                               engine volume
Specific volume = -----------------------------------
                               rated power

For these parameters to be useful in engine comparisons, a consistent definition of what components
and auxiliaries are included in the term "engine" must be adhered to. These parameters indicate the effectiveness with which the engine designer has used the engine materials and packaged the engine components.

when we use turbocharger as a method to increase the power output of the engine,so we can get more power for the same size of engine,as we will see when we talk about turbocharged engines.

In this table "source is wikipedia " we see for example the difference between turbocharged engine and ordinary engine.

Engine	Power to weight ratio
Turbocharged V-8 diesel engine	0.25 hp/lb / 410 W/kg
Boeing 777 GE90-115B Jet Engine	7.63 hp/lb / 12,513 W/kg
Space shuttle turbopump	100 hp/lb / 164120 W/kg