The aluminium engine can be
described as a regular four
stroke engine where aluminium is used to form the major parts of
the engine. Different engines will have various amounts of aluminium
parts. The parts in many cases are not pure aluminium as aluminium
alloys are also used to form the various components of the
engine. Aluminium is a very light metal weighing
approximately one third the weight of steel but it was not
introduced to engines due to it's lightweight properties.
Although aluminium is much lighter than iron and steel it was first
used on engine heads because of it's better cooling properties as
the engine head contains most of the moving parts which includes the
valves, springs and camshafts.
The cylinder head may have many moving parts but it is small in
relation to the entire size of the engine so an aluminium engine
head was more expensive but still feasible.
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The engine block however is another
story. The block forms a lot of the mass and weight of the
engine so using aluminium to build engine blocks reduces the
weight of the engine by many kilograms and assists the vehicle
in obtaining a better power to weight ratio and assists in
achieving a front to rear weight ratio of 50:50 or close to
it. Due to the size of the block in relation to the
entire engine, the cost of an aluminium engine block is
significantly higher and is used on vehicles where the overall
cost is not much of an issue.
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Pistons are also made of aluminium as the lighter pistons require
less energy to be moved up and down during the four stroke cycle and
this facilities higher revs. The issue with this is these pistons
can't be used with the aluminium engine block as contact between two
aluminium surfaces creates large amounts of friction so one must be
cast iron, either the piston or the block. The common solution for
this problem was to line the cylinder walls with cast
iron. Aluminium is also used in intake manifolds to reduce
their weight but another benefit is noise reduction. Heat resistant
plastic is also used to make intake manifolds, its cheaper than
aluminium and is lightweight. The problem with the plastic manifolds
is that they generate noise as the air flows through them so luxury
vehicles use aluminium or magnesium manifolds, both are lightweight
without the noise. Aluminium engines are becoming widely used
in the automotive industry. The amount of parts used will vary with
the manufacturer and the model of vehicle. Aluminium is also being
used in other parts of the vehicle such as the chassis
and the body of some high end vehicles.
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