The power generated by the internal combustion engine
is directly related to the amount of air that is compressed in the
cylinders. In other words, the greater the compression, the greater
output of the engine.
Two approaches can be used to increase engine
compression. One is to modify the engine to increase the compression
ratio. This has been done in many ways including the use of such things
as domes or high top pistons, altered crankshaft strokes, or changes in
the shape and structure of the combustion chamber.
less expensive way to increase compression (and engine power) without
physically changing the shape of the combustion chamber is to simply
increase the intake charge. By pressurizing the intake mixture before it
enters the cylinder, more air and fuel molecules can be packed into
Increases in horsepower are normally evidenced by an
engine¡¯s response to a quick opening of the throttle. The lack of
throttle response is felt with some turbocharged systems. This delay or
turbo-lag occurs because exhaust gas require a little time to build
enough energy to spin the blower up to speed.
The variable nozzle turbine (VNT) has greatly
improved the turbo-lag traditionally associated with turbochargers.
Turbo lag occurs when the turbocharger is unable to meet immediate
demands of the engine. This causes the power from the engine to
temporarily lag behind the need. VNT units allow the turbine to
accelerate more quickly than the conventional turbos thereby reducing
the lag time.