Forced induction is a term used to describe internal combustion engines that are not naturally aspirated. Instead, a gas compressor is added to the air intake, thereby increasing the quantity of oxygen available for combustion. This compressed air is normally referred to as Boost or charge air. A colorized automobile engine The internal combustion engine is a heat engine in which the burning of a fuel occurs in a confined space called a combustion chamber. ... A naturally-aspirated engine or normally-aspirated engine (NA - aspiration meaning breathing) refers to an internal combustion engine (normally petrol or diesel powered) that is neither turbocharged nor supercharged. ... A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. ... Boost in automotive engineering is a positive manifold pressure in cars with turbochargers or superchargers. ...

Introduction

Forced induction can be used to increase the power of an engine, its efficiency, or both, without much extra weight. The ambient air that the engine is normally ingesting enters the compressor inlet of turbocharger or supercharger that is inline along the air intake tract. This effectively decreases the mass of the air, which allows for a much greater percentage of oxygen per volume of air intake to be added to the air/fuel mixture. The effects are an increase to the effective capacity of the engine without an increase in physical size. The forced induction approach has the advantage that the intake pressure may be regulated according to the engine speed, thus providing power from extra capacity at high speed, but without wasting fuel at lower speeds.

Two of the commonly used forced induction technologies are superchargers and turbochargers. They differ mainly in the power source for the compressor. Turbochargers are driven by the exhaust gases of the engine, whereas superchargers are driven by a belt connected to the crankshaft of the engine. A supercharger (also known as a blower) is an air compressor used to compress air into the cylinders of an internal combustion engine. ... Air foil bearing-supported turbocharger cutaway made by Mohawk Innovative Technology Inc. ...

Comparison

Strengths and weaknesses vary according to the method of forcing induction largely based upon the inherent design functions of both. A turbocharger acts as an obstacle to exhaust gases due to its placement in the exhaust system tract. A supercharger uses horsepower from the rotational mass internal to the engine through the crank pulley. A turbo relies on the volume and velocity of exhaust gases to spool, or spin the compressor fast enough to compress the intake to a desired amount. The amount of time that it takes a turbocharger to reach the onset of boost is referred to as lag. A supercharger is 'on' all of the time, meaning that it is capable of producing the amount of desired boost instantly. It is easier to target a desired boost with a turbocharger as there are many forms of boost controllers that allow a user to adjust to desired boost fairly easily. In order to achieve desired boost with a supercharger, a larger or smaller pulley must be installed.

Intercooling

A fundamental to forced induction is that compressing air raises its temperature very quickly. As a result, the highly dense charge is reduced and the cylinders receive less fresh air than the system’s boost pressure prescribes. The risk of knock in internal combustion engines also increases. These drawbacks are countered by charge-air cooling, which passes the air leaving the turbocharger or supercharger through a special cooler (called intercooler for turbochargers and aftercooler for superchargers), air intake is increased and the thermal load is reduced. The first law of thermodynamics, a generalized expression of the law of the conservation of energy, states: // Description Essentially, the First Law of Thermodynamics declares that energy is conserved for a closed system, with heat and work being the forms of energy transfer. ... It has been suggested that Detonation internal combustion engine be merged into this article or section. ... A front-mounted intercooler on a Mitsubishi Eclipse An intercooler is a device used on turbocharged and supercharged internal combustion engines to improve the volumetric efficiency, increase the amount of charge in the engine, and lower charge air temperature thereby increasing power and reliability. ... For the Australian rock group, see Intercooler-(band). ...

Alcohol/Water Injection

Additionally, alcohol injection is an effective means of cooling the charge air. Methanol is the preferred alcohol due to its elemental properties, and is normally mixed with water and injected pre-intake manifold. Methanol, unlike nitrous oxide or forced induction itself, doesn't add more oxygen to the charge, but by using up to 40 percent alcohol to 60 percent water, additional cooling takes place before the turbo, and the alcohol works as a fuel in the charge. This results in an increase in power. Gasoline on the left, alcohol on the right at a filling station in Brazil Rising energy prices and environmental problems have led to increased interest in alcohol as a fuel. ... R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ...

Nitrous oxide is not considered forced induction as it does not increase pressure into the intake. It does however, increase the quantity of oxygen available for combustion. R-phrases S-phrases Supplementary data page Structure and properties n, εr, etc. ...

Like was stated above, adding forced induction increases the amount of air an engine can use for combustion, in effect allowing more fuel to be used with the available oxygen. Further, it increases an engine's dynamic compression ratio. As compression ratio increases, so does the threat of knock and therefore the need for higher octane fuel. The compression ratio is a single number that can be used to predict the performance of any engine (such as an internal-combustion engine or a Stirling Engine). ...