Supercharger: Description and Operation
Supercharger (MINI COOPER S only)
the MINI COOPER S is fitted with a "state of the art" supercharger that has been specifically engineered for small engines. It was designed as a compact unit with the ability to provide the performance that is synonymous with the COOPER S name.
Supercharger Operation
the supercharger is a positive displacement pump. Its purpose is to increase air pressure and density in the intake manifold. the supercharger is matched to the engine by its displacement and belt ratio (driven from the crankshaft).
the concentrated charge of air provided by the supercharger results in a more powerful combustion stroke in the engine's cylinders, resulting in improved performance over non-supercharged engines.
the supercharger incorporates a specially designed bypass valve. This is actuated by a vacuum pipe near the throttle body and re-circulates the supercharger air when boost is not required.
During typical driving conditions the intake manifold is under pressure for only 5% of the time.
For the remaining time the intake manifold is under vacuum (negative pressure), allowing for better fuel economy and a quieter ride.
Inside the supercharger the helix angled rotors and specially designed inlet and outlet port geometry reduce pressure variations. This results in a smooth discharge flow and a lower level of noise during operation. the way in which the dueling to and from the supercharger is mounted also plays a major role in reducing noise.
Inter-cooler (MINI COOPER S only)
Heat exchangers, now more commonly known as intercoolers, were originally used on large diesel engines in conjunction with a blower (supercharger). the intercooler construction is similar to that of the engine radiator.
Advantages of an intercooler.
- Increases mass/density of air change entering the cylinders.
- Helps keep cylinder head temperature lower.
- Reduces oxides of nitrogen.
There are two types of intercooler.
- Air to liquid intercooler.
- Air to air intercooler.
MINI COOPER S uses an air to air intercooler. the major advantage of the air to air intercooler over the air to liquid intercooler is its capacity to reduce the temperature of the compressed air charge to around 40-50°C.
Operation
When the compressed air mass leaves the outlet of the supercharger, the molecules of air are tightly packed together which generates heat. the air is forced into the inlet of the intercooler and is passed through many elongated tubes.
the ram air effect takes place as the vehicle moves forward and outside air passes externally over the elongated tubes cooling the compressed charge sufficiently before leaving the intercooler.
Location
the intercooler is located directly on top of the supercharger. It is mounted by 2 top hat brackets at the front, with the rear of the intercooler solidly mounted.
