To increase the power from your engine you can increase the size of the engine (swept volume) or increase the mass of the air/fuel charge compressed in the cylinders by using a supercharger or a turbocharger.
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 Increase
the Engine Size |
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 To
develop more power you can increase the engine size so that a greater mass
of air/fuel is burnt. This results in higher fuel costs as more fuel is
burnt. Also the engine is heavier/larger as the vehicle is carrying more
load and the vehicle needs to be larger to take the engine. At high altitudes,
there is insufficient oxygen to burn the fuel, resulting in low power and
black smoke. |
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Supercharge |
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A
supercharger increases the pressure of the air in the inlet manifold
of the engine. As the air pressure is greater than atmospheric pressure
it has a higher density i.e. more oxygen per litre of air. When the inlet
valve in the cylinder opens a greater mass of air rushes into the cylinder
to be burnt with the fuel. More power is generated at each engine speed
but the supercharger is driven direct from the engine. So, theoretically
a supercharger could increase a 200hp engine to a 275hp engine. However
as it is an engine parasite it needs 50hp to operate therefore only increases
the engine to 225hp. |
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Turbocharge |
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 A
turbocharger acts in a similar way as a supercharger and pressurises
the air at the inlet manifold. As the inlet valve in the cylinder opens,
a greater mass of air is drawn into the cylinder to be burnt with the
fuel. More power is generated at each engine speed.
Unlike the supercharger
it does not feed off the power output of the engine. The turbocharger
uses the waste energy from the exhaust gas to drive a turbine wheel that
is linked to the compressor through a shaft.
At high altitudes the turbocharger rotates faster to increase delivery of air
to the engine to compensate. So a turbocharger maintains power from the engine
and produces clean emissions.
Fitting a turbocharger and an air cooler can increase engine power even more.
An Intercooler removes the heat of compression between the stages of a compressor
whereas an aftercooler reduces the temperature of the air leaving the compressor.
Delivering cold air means that there is more oxygen per cylinder (cold air has
a higher density than warm air) thus more engine power. |
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To conclude, the benefits of turbocharging are:
 increased engine power output (in the region of 50% increase)
improved fuel consumption (improved pressure balance across the engine)
improved emissions
altitude compensation |
