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.
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.
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.