VVT
(Variable Valve Timing)
The
intake and exhaust valves are used to open and close the ports which
allow fuel and air into the combustion chamber, and exhaust gasses
out. Depending on the size of the opening, and the duration they
are opened for, more fuel and air can be let in and the faster the
exhaust gasses expelled.
The opening size and time is regulated by the lobes on the camshaft,
and in most engines the parameters are set staying the same throughout
the entire rpm range, they can only be changed by swapping the camshaft.
In engines equipped with VVT, at higher rpms a more extreme profile
lobe is activated which then overrides the normal use lobes of the
camshaft. This causes the valves to remain open for longer and at
a greater distance. The benefits include higher performance when
required but standard fuel economy during normal driving conditions.
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