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Introduction
Turbochargers showcase innovation in automotive technology, boosting power and efficiency for a thrilling driving experience. They are essential for high-performance engines, giving extra power to both enthusiasts and efficiency-minded drivers. This blog delves into turbochargers, examining their mechanics, advantages, and influence on contemporary engines.
Understanding Turbochargers
A turbocharger, or turbo, forces more intake air—and proportionately more fuel—into the combustion chamber, allowing an engine of a given size to produce more power. By increasing the air-fuel mixture density, a turbocharged engine delivers greater power and efficiency compared to a naturally aspirated one. Manufacturers commonly use turbos in trucks, cars, trains, and construction equipment. Turbos also frequently pair with internal combustion engines operating on the Otto and Diesel cycles.
There are two ways of increasing the power of an engine. One of them would be to make the fuel-air mixture richer by adding more fuel. This will increase the power but at the cost of fuel efficiency and increase in pollution levels… prohibitive! The other would be to somehow increase the volume of air entering into the cylinder and increasing the fuel intake proportionately, increasing power and fuel efficiency without hurting the environment or efficiency. This is exactly what Turbochargers do,increasing the volumetric efficiency of an engine.
In a naturally aspirated engine, the downward stroke of the piston creates an area of low pressure in order to draw more air into the cylinder through the intake valves. Now because of the pressure in the cylinder cannot go below 0 (zero) psi (vacuum) and relatively constant atmospheric pressure (about 15 psi) there will be a limit to the pressure difference across the intake valves and hence the amount of air entering the combustion chamber or the cylinder.
The ability to fill the cylinder with air is its volumetric efficiency. Now if we can increase the pressure difference across the intake valves by some way we can make more air enter into the cylinder and hence increasing the volumetric efficiency of the engine.
It increases the pressure at the point where air is entering the cylinder, thereby increasing the pressure difference across the intake valves and thus more air enters into the combustion chamber. The additional air makes it possible to add more fuel, increasing the power and torque output of the engine,particularly at higher engine speeds.
Turbochargers were originally known as Turbo superchargers when all forced induction devices were classified as superchargers; nowadays the term "supercharger" is usually applied to only mechanically driven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that the latter is mechanically driven from the engine, often from a belt connected to the crankshaft, whereas a turbocharger is driven by the engine's exhaust gas turbine. Compared to a mechanically driven supercharger, turbochargers tend to be more efficient but less responsive.
History of turbochargers
The turbocharger was invented by Swiss engineer Alfred Büchi. His patent for a turbocharger was applied for use in 1905. Diesel ships and locomotives with turbochargers began appearing in the 1920s.During the First World War French engineer Auguste Rateau fitted turbochargers to Renault engines powering various French fighters with some success. In1918, General Electric engineer Sanford Moss attached a turbo to a V12 Liberty aircraft engine. The engine was tested at Pikes Peak in Colorado at 4,300 m to demonstrate that it could eliminate the power losses usually experienced in internal combustion engines as a result of reduced air pressure and density at high altitude.
Turbochargers were first used in production aircraft engines in the 1920s,although they were less common than engine-driven centrifugal superchargers. The primary purpose behind most aircraft-based applications was to increase the altitude at which the airplane could fly, by compensating for the lower atmospheric pressure present at high altitude.
The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer(Swiss Machine Works Saurer) in 1938 .The first production turbocharged automobile engines came from General Motors in 1962. At the Paris auto show in1974, during the height of the oil crisis, Porsche introduced the 911 Turbo – the world’s first production sports car with an exhaust turbocharger and pressure regulator.
This was made possible by the introduction of a waste gate to direct excess exhaust gasses away from the exhaust turbine. The world's first production turbo diesel automobiles were the Garrett turbocharged Mercedes 300SD and the Peugeot 604, both introduced in 1978. Today, most automotive diesels are turbocharged.
How Turbochargers Work
A turbocharger aims to achieve the same goal as a supercharger: to improve the engine's volumetric efficiency by overcoming a key limitation. In a naturally aspirated engine, the downward stroke of a piston creates a low-pressure area that draws air into the cylinder through the intake valves. However, since atmospheric pressure reaches only about 1 atm (approximately 14.7 psi), the pressure difference across the intake valves—and therefore the airflow entering the combustion chamber—remains limited.
Because the turbocharger increases pressure at the cylinder intake point, it forces a greater mass of air (oxygen) into the engine as inlet manifold pressure rises. The engine uses this additional airflow to maintain combustion chamber pressure and fuel/air load even at high RPMs, which increases both power and torque output.
To prevent detonation and physical damage, the system must limit cylinder pressure by controlling intake pressure. A waste gate performs this control function by routing some of the exhaust flow away from the turbine. This action regulates the air pressure in the intake manifold.
Now we will know about turbo lag and boost.
Turbo lag and Boost
- Drivers notice this as a hesitation in throttle response when coming off idle. The exhaust system takes time to build high pressure and the turbine rotor needs time to overcome its rotational inertia and reach the speed necessary to supply boost pressure.
- The directly driven compressor in a supercharger avoids this problem. Conversely, under light loads or at low RPM, a turbocharger supplies less boost, causing the engine to behave like a naturally aspirated one. Turbochargers begin producing boost only after the exhaust reaches a certain mass flow rate, which depends on the turbo size.
- Without an appropriate exhaust gas flow, the turbocharger cannot force air into the engine. The engine reaches the boost threshold RPM at full throttle, where the exhaust mass flow becomes strong enough to push air into the intake. Engineers sometimes reduce this threshold to idle speed to achieve instant response. One can determine both lag and threshold characteristics using a compressor map and mathematical equations.
Components of a turbocharger
The turbocharger consists of four main components. The turbine (typically a radial turbine) and the impeller or compressor wheels sit in separate folded conical housings on opposite sides of the center housing or hub rotating assembly. The housings around the compressor impeller and turbine direct and manage the gas flow through the spinning wheels.
The size and shape of the components influence several performance characteristics of the turbocharger. The turbine and impeller wheel sizes determine how much air or exhaust flows through the system and how efficiently they operate. In general, larger turbine and compressor wheels allow greater flow capacity.
The center hub rotating assembly houses the shaft which connects the compressor impeller and turbine. It also must contain a bearing system to suspend the shaft, allowing it to rotate at very high speed with minimal friction. Waste gates for the exhaust flow.
1.Turbine wheel
2.Compressor wheel (Impeller)
Manufacturers use a modified version of the aluminum investment casting process to produce compressor impellers. They create a rubber replica of the impeller to form the casting mold, then remove the rubber before pouring the metal. Precision in blade sections and profiles ensures optimal compressor efficiency. Machining the back face profile reduces impeller stress. Tight-tolerance boring and burnishing help balance the impeller and improve fatigue durability. A threaded nut secures the impeller on the shaft assembly.
3.Waste gases
Advantages
- More specific power over naturally aspirated engine. This means a turbocharged engine can achieve more power from same engine volume.
- Turbocharged engines deliver better thermal efficiency than both naturally aspirated and supercharged engines under full load (i.e., on boost). This happens because the system uses excess exhaust heat and pressure—normally wasted—to help compress the air.
- Turbochargers weigh less and take up less space than alternative forced induction systems, making them easier to fit in an engine bay.
- Fuel economy improves indirectly with turbochargers. Although a turbocharger doesn't directly save fuel, it allows a vehicle to run a smaller engine that still produces the power of a larger one. While cruising or driving off-boost, the engine uses less fuel to maintain the proper air-fuel ratio, which helps achieve near-normal fuel economy.
Disadvantages
- Lack of Responsiveness is Using an incorrectly sized turbocharger can reduce throttle response. A turbo that's too large builds boost slowly, leading to noticeable "lag." While this setup may deliver higher peak power, it sacrifices low-end responsiveness and drivability.
- A turbocharger’s boost threshold means it only generates boost after the engine reaches a certain RPM, as low exhaust flow at low speeds can’t overcome turbo inertia. This causes a sudden torque surge, narrowing the power band. The abrupt power can reduce traction, leading to understeer or oversteer based on drivetrain and suspension. In racing, boost lag is a drawback—mid-turn throttle can trigger sudden power spikes and wheel spin.
- Cost of Turbocharger parts add significant expense when installed on naturally aspirated engines. Heavily modifying OEM turbocharger systems often demands extensive upgrades, usually replacing most or even all of the original components.
- Complexity- Beyond cost, turbochargers need several extra systems to avoid engine damage. Even with light boost, turbochargers require proper oil routing, a turbo-specific exhaust manifold, a custom downpipe, and boost control. Intercooled setups need added plumbing, while high-performance systems demand upgraded lubrication, cooling, intake, and reinforced engine and transmission parts.
Application
1.Gasoline-powered cars
2.Diesel-powered cars
3.Motorcycle
4.Trucks
5.Aircraft
Turbochargers are ideal for aircraft engines. At 5,486 meters (18,000 feet), air pressure drops to half, reducing drag but also cutting power in naturally aspirated engines. Turbochargers restore lost power, enabling better performance at high altitudes.
The main objective is to maximize the efficiency of non-renewable energy sources such as petrol and diesel. Achieving complete combustion of the fuel leads to a noticeable increase in power output. Additionally, integrating wind energy for air compression supports improved combustion by supplying denser, pressurized air to the engine. This enhanced air-fuel mixture promotes more effective energy conversion. Observations show these improvements can increase engine power and efficiency by 10–15% and help reduce harmful emissions.
At full throttle, the engine hits 4000 rpm, and the turbocharger delivers 1.60 bar of pressurized air. Unlike naturally aspirated engines that depend on atmospheric pressure, turbocharged engines provide high-density air, enhancing air-fuel mixing, combustion, and efficiency.
Conclusion
Turbochargers have transformed the automotive industry by offering more power and better efficiency in a variety of vehicles. The industry's embrace of turbocharging shows a dedication to balancing performance and fuel economy. Turbochargers play a key role in advancing automotive technology toward faster, more efficient, and environmentally friendly cars. Get ready for the ever-growing impact of turbocharged engines.