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A “turbocharger” is simply a gas pressure turbine unit connected to a centrifugal air compressor, with the turbo vane and compressor impeller mounted on a shared rotating center shaft. In a turbocharged engine, hot pressurized exhaust is directed to a turbine transmission normally mounted on the engine’s exhaust manifold, the pressure from the exhaust that spins the turbine transmission on its way out of the exhaust manifold. The rotating pressure vane rotates the air compressor, which in turn creates “boost pressure.” Compressed air is measured in pounds per square inch, also known as “pounds of boost.” Typically the compressed air is piped through an internal cooler and then to the engine intake manifold.
The desired benefit of compressing the engine intake air is so that you can add more fuel to the intake charge, the more air you can introduce into the combustion chamber, the more fuel you will add to maintain an optimal fuel / air ratio for the maximum power. A major drawback of compressed air is that it heats up due to increased molecular friction during the compression process, as a result, warmer air temperatures will cause the engine to produce less horsepower.
To remedy this, you must cool the compressed air by passing it through an air cooler (intercooler) before it enters the combustion chamber. The “intercooler” is generally mounted on the lower front of the car in front of the radiator for maximum cooling efficiency.
In certain cases, some people choose to employ a “twin turbo system”, the main reason for this is to reduce “turbo lag” and still provide good high-end boost pressure. Lagging occurs at low engine RPM when the exhaust manifold pressure is too low and does not produce enough pressure to turn the air compressor fast enough for optimal boost.
There are two types of twin turbo systems, “Parallel and Sequential”, the most common “parallel” systems employ 2 smaller diameter turbochargers of equal flow capacity always running at the same time, with one connected to the exhaust manifold on each bank. . of cylinders, most commonly used in V-style engines. Two small turbos require less pressure and time to “roll up” (reach optimal speed / pressure) while still producing a high volume of airflow and dramatically reducing lag time. The other type is sequential, this system, although less common, also uses 2 turbochargers, only in this case one has a greater flow capacity than the other. The smallest primary turbo is the first to wind, after the smallest one is wound it will build pressure in the system which will cause the secondary (large diameter) to wind as well.