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Turbocharging
The turbocharger is a device which increases the output power of a normally aspirated engine. It was invented by Swiss engineer Alfred Büchi. His patent for a turbo charger was applied for use in 1905. Diesel ships and locomotives with turbochargers began appearing in the 1920s.
Working principle of a Turbocharger
A turbocharger consists of a turbine and a compressor linked by a shared axle. The turbine inlet receives exhaust gases from the engine causing the turbine wheel to rotate. This rotation drives the compressor, compressing ambient air and delivering it to the air intake manifold of the engine at higher pressure, resulting in a greater amount of the air entering the cylinder. In some instances, compressed air is routed through an intercooler before introduction to the intake manifold.
The objective of a turbocharger is the same as a supercharger; to improve upon the size-to-output efficiency of an engine by solving one of its cardinal limitations. A naturally aspirated automobile engine uses only the downward stroke of a piston to create an area of low pressure in order to draw air into the cylinder through the intake valves. Because the pressure in the atmosphere is no more than approximately 14.7 psi, there ultimately will be a limit to the pressure difference across the intake valves and thus the amount of airflow entering the combustion chamber. This ability to fill the cylinder with air is its volumetric efficiency. Because the turbocharger increases the pressure at the point where air is entering the cylinder, a greater mass of air will be forced in as the inlet manifold pressure increases. The additional air makes it possible to add more fuel, increasing the power and torque output of the engine.
Because the pressure in the cylinder must not go too high to avoid detonation and physical damage, the intake pressure must be controlled by controlling the rotational speed of the turbocharger. The control function is performed by a wastegate, which routes some of the exhaust flow away from the exhaust turbine. This controls shaft speed and regulates air pressure in the intake manifold.
The application of a compressor to increase pressure at the point of cylinder air intake is often referred to as forced induction. Centrifugal superchargers compress air in the same fashion as a turbocharger. However, the energy to spin the supercharger is taken from the rotating output energy of the engine's crankshaft as opposed to normally exhausted gas from the engine. Superchargers use output energy from an engine to achieve a net gain, which must be provided from some of the engine's total output. Turbochargers, on the other hand, convert some of the piston engine's exhaust into useful work. This energy would otherwise be wasted out the exhaust. This means that a turbocharger is a more efficient use of the heat energy obtained from the fuel than a supercharger.
Production Automobiles
The first Turbo-Diesel truck was produced by the "Schweizer Maschinenfabrik Saurer" (Swiss Machine Works Saurer) 1938 [1].
The Corvair's innovative turbocharged flat-6 engine. The turbo, located at top right, feeds pressurized air into the engine through the chrome T-tube visible spanning the engine from left to right.
The first production turbocharged automobile engines came from General Motors in 1962. The A-body Oldsmobile Cutlass Jetfire and Chevrolet Corvair Monza Spyder were both fitted with turbochargers.
The world's first production turbodiesel automobile was also introduced in 1978 by Mercedes-Benz with the launch of the 300SD turbodiesel. Today, nearly all automotive diesels are turbocharged.
Competition cars
The turbocharger first hit the automobile racing world in 1952 when Fred Agabashian qualified for pole position at the Indianapolis 500 and led for 100 miles (160 km) before tire shards disabled the compressor. Offenhauser's turbocharged engines returned to Indianapolis in 1966, with victories coming in 1968. The Offenhauser turbo peaked at over 1,000 hp (750 kW) in 1973, while Porsche dominated the Can-Am series with a 1,100 hp (820 kW) 917/30. Turbocharged cars dominated the Le Mans between 1976 and 1988, and then from 2000-2007.
In Formula One, in the so called "Turbo Era" of 1977 until 1989, engines with a capacity of 1500 cc could achieve anywhere from 1000 to 1500 hp (746 to 1119 kW) (Renault, Honda, BMW, Ferrari). Renault was the first manufacturer to apply turbo technology in the F1 field, in 1977. The project's high cost was compensated for by its performance, and led to other engine manufacturers following suit. The Turbo-charged engines took over the F1 field and ended the Ford Cosworth DFV era in the mid 1980s. However, the FIA decided that turbos were making the sport too dangerous and expensive, and from 1987 onwards, the maximum boost pressure was reduced before the technology was banned completely for 1989.
In Rallying, turbocharged engines of up to 2000 cc have long been the preferred motive power for the Group A/World Rally Car (top level) competitors, due to the exceptional power-to-weight ratios (and enormous torque) attainable. This combines with the use of vehicles with relatively small bodyshells for manoeuvreability and handling. As turbo outputs rose to similar levels as the F1 category (see above), the FIA, rather than banning the technology, enforced a restricted turbo inlet diameter (currently 34 mm).
