Simply put, a turbocharger is a type of air pump that takes air at ambient pressures (atmospheric pressure), compresses it, and feeds the compressed air into the engine through the inlet valves. In general, turbos have been more commonly used on diesel engines to boost performance in cars and vans, but there is now a shift toward turbocharging production petrol engines to meet ever-tightening emissions control.
Because all engines require air and fuel, we know that increasing either of these factors within certain limits will increase engine power; however, if we increase the fuel, we must be able to burn off all of it or the mixture will become too rich, which can cause a variety of issues. Similarly, “running too lean,” or taking in too much air, is harmful.
We need air for this to work, but adding more air is much more difficult than adding more fuel. We are constantly surrounded by pressurized air (around 15 p.s.i. at sea level), and it is this pressure, in conjunction with the engine’s induction stroke, that forces air into the cylinders. To increase airflow, compressed air is blown into the engine via an air pump (turbocharger). The increased efficiency of the fuel burned due to the addition of air to the injected fuel results in a higher overall power output of the engine.
An engine that routinely operates at high altitudes, where the air is less dense, and where turbocharging can restore some of the power lost due to the drop in air pressure, may also be of interest, as it provides yet another benefit of turbocharging. An engine produces only 75% of its rated output at 8,000 feet.
Combustion byproducts that are extremely hot are diverted away from the exhaust and into the turbocharger. Since the cylinders in an internal combustion engine do not all ignite simultaneously, the exhaust is released in sporadic bursts rather than a steady stream. Regular single-scroll turbochargers channel the exhaust in pulses, which collide and weaken the flow as they enter the turbine. A twin-scroll turbocharger, on the other hand, collects exhaust from alternate pairs of cylinders.
The exhaust flows into the turbine, where it collides with the blades and spins them at speeds of up to 150,000 revolutions per minute. In order to prevent turbo lag, the exhaust is pulsed on and off constantly.
After being used up, the vehicle’s exhaust gases are routed through an outlet and into a catalytic converter, where they are purified by removing harmful gases like carbon monoxide and nitrous oxide before being released through the tailpipe.
At the same time, the turbine drives an air compressor that pulls in chilly, fresh air from a vent and squeezes it to nearly 19 psi (or 30% above atmospheric pressure). Air dense with oxygen enters the combustion chamber. Because of the increased oxygen content, the fuel can be burned more completely, allowing the engine to produce more power with the same displacement. Because of this, the TwinPower engine produces 30% more power than a similarly sized engine without turbocharging.