A turbocharger is a centrifugal compressor which is powered by a turbine and driven by the exhaust gases of an engine. The compressor increases the pressure of air which enters the engine, yielding better performance. The technology is used mainly in case of internal combustion engines like four-stroke engines and sports cars, to multiply the performance of smaller engines into efficient powerplants. All the modern diesel engines use the technology. Automobile companies have found a way to improve the performance of turbochargers by introducing twin-turbochargers. The twin-turbochargers used in the Nissan GT-R helps to generate horsepower of 523 from a 3.8 liter engine with mileage of 23 mpg. The reduced emissions of 279 gms/km, is actually quite remarkable.
Use of Smaller Engines
Using smaller engines helps in making a car environment friendly and fuel efficient, though only to an extent. A vehicle which is too heavy may cause a small engine to breakdown, as an engine in case of any automobile, takes the onus for moving a vehicle. The consumption of fuel shoots up in such a case to make up for the small strength. Car makers are currently working on ways to enhance the power and efficiency of small engines to combine fuel efficiency with performance. One such effort shows in the Fiat
500 city car. The 900 CC, two-cylinder Twinair engine gives out 83 hp and CO2 emissions of 92 gms/km.
High-Pressure direct injection
The high-pressure direct injection system (HDi) technology is more expensive than indirect injection as the injectors are exposed to more heat and pressure. The technology is however more efficient, contributing towards a cleaner system. The fuel is fired directly into the cylinders of the engine at very high pressure, creating an optimum mix of fuel and air, aiding quick ignition. The injectors are controlled with high precision during various points of the combustion cycle, allowing the engine to adapt to the needs of the drivers, helping in enhancing performance and economy. The direct injection system also maximizes the energy derived from each drop of fuel, making them a popular feature in most of the recently launched vehicles. PSA Peugeot Citroen has used the technology to reduce the CO2 emissions by 20% as compared with an old generation diesel engine and by 25% in case of a petrol engine. The engine is also found to contribute towards noise reduction and driving comfort. Other companies to use the technology include the FSI Audi
and the JTS units of Alfa Romeo.
Variable Valve Timing
The Variable Valve Timing (VVT) technology, also known as Variable Valve Actuation, is a generalized term used to describe a mechanism which can alter the shape and timing of a valve shift within an internal combustion engine. The ways to achieve VVT include mechanical to electro hydraulic and camless systems while a power valve system is used to achieve the same results in a two-stroke engine. The system uses a computer control unit which adapts itself according to the driver of the car, performing better over a wider spread of engine speeds. The technology is found to enhance the performance of an engine while improving the fuel efficiency and emissions. The technology has been popularly employed in some of the petrol engines of Honda’s i-VTEC, the Toyota Valvematic and the Bi-VANOS of BMW.
HCCI or Homogenous Charge Compression Ignition is a form of internal combustion which compresses an optimum mix of fuel and oxidizer, to aid auto-ignition. The exothermic reaction releases chemical energy into a sensible form to generate heat, igniting the engine to get working. HCCI technology also contributes to 15% to 30% better fuel efficiency as compared to a spark-ignition petrol engine apart from giving out lesser quantities of harmful emissions. The technology operates with a compression ratio of a diesel engine, improving on efficiency. HCCI engines are highly adaptable, with an ability to work on gasoline, diesel and most of the alternative fuels. Considered as a next-generation offering, the technology is attracting the attention of car-makers who are bullish on employing the HCCI technology, which is currently still under development. Experts in the field however opine that the technology could lead to peak in-cylinder pressures, causing damage and greater engine wear. It is yet to be seen if the CO and HC pre-catalyst emissions in the technology are lower than a typical spark ignition engine.