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Which Types of Turbochargers are Best? Pros & Cons [PDF]

In this article, you will learn how does a turbocharger works? And their advantages, disadvantages, and different types of turbochargers. As always you can download the PDF file of this article at the end.

What is Turbocharger?

A turbocharger, (or turbo), is a piece of turbine-driven forced induction equipment, that increases the efficiency and power output of an internal combustion engine by forcing excess air into the combustion chamber.

Typically, a turbo sucks air, cools it down, and then feeds more air to the engine than it receives through its standard intake. Nevertheless, turbochargers can be deep and impenetrable to fully understand their internal functioning. A turbocharger is a tiny turbine that lies between the engine and exhaust.

Due to the air intake of both as well as the car, a turbocharger uses exhaust gases to spin the turbine which then forces more air into your car’s engine and increases the power of the car.

The turbocharger is consists of a compressor wheel, a turbine wheel, two ports for the air inlet and air outlet, and two ports for the exhaust inlet and exhaust outlet. Now let’s discuss how the turbocharger works in your car engine.

How Does Turbocharger Works?

The turbocharger on the car applies the same working principle as the piston engine. A turbocharger usually consists of a turbine section and compressor section. A turbine section has a turbine wheel to convert the energy and turbine housing to protect it.

Working of Turbocharger
Image: Eagle Ridge GM

The purpose of using turbine housing is to guide the exhaust gas into the turbine wheel. The energy released from the exhaust gas causes the turbine wheel to spin, and so the gas leaves the turbine housing through an exhaust outlet area.

Now, the compressor section also includes the compressor wheel to convert some of the energy and the compressor housing for protection. The mode of action of the compressor is opposite to that of the turbine.

A compressor wheel is connected to the turbine by a forged steel shaft, and as the turbine turns the compressor wheel, the high-velocity spinning pulls in the air and compresses it as a result.

Then, the compressor housing turns the high-velocity, low-pressure air stream into a high-pressure, low-velocity air stream by a process termed diffusion. And finally, compressed air is pushed into the engine, causing the engine to burn more fuel to produce more energy.

Types of Turbochargers

Following are the types of turbochargers used in automobiles:

  1. Single-Turbo
  2. Twin-Turbo
  3. Twin-Scroll Turbo
  4. Variable Geometry Turbo
  5. Variable Twin Scroll Turbo
  6. Electric Turbo

1. Single-Turbo

A single turbocharger is the most people think of like a turbo. By varying the size of the components within the turbo, quite separate torque characteristics can be obtained. The larger turbos give higher levels of top-level power, while tinier turbos can spool quicker and produce better low-end power.

They are costly to increase engine power and efficiency, and as have become more popular, allow small engines to increase efficiency by naturally producing the same power as larger engines, but with less weight.

However, they work best in a narrow RPM range, and drivers will usually feel “turbo-lag” till the turbo starts operating within its peak rev band.

Advantages of Single-Turbo Disadvantages of Single-Turbo
It is cost-effective for increasing the power and efficiency of the engine.The single turbo has a somewhat narrow effective RPM range. This creates a problem, as you have to choose between good low-end torque or better high-end power.
It is the simplest type of turbocharger and is usually easy to install.The response of a single turbo maybe not fast as the other types of turbos.
Single-turbos are used for smaller engines to produce the same power as larger engines. So, they can often reduce weight.

2. Twin-Turbo

Types of Turbocharger - Twin Turbo
Image: Wikipedia

In a twin-turbo turbocharger, there is a second turbocharger to the engine. In a V6 or V8 engine, this can be done by allowing a single turbo to work with each cylinder bank. Alternatively, a smaller turbo can be applied at lower RPMs with a larger turbo for higher RPMs.

The second configuration allows for a wider operating RPM range, and gives better torque at lower revs (reducing turbo lag), but also power at higher RPM, it is also known as twin sequential turbocharging. Unexpectedly, having two turbos greatly increases complexity and costs.

Advantages of Twin-TurboDisadvantages of Twi-turbo
The benefits and drawbacks are similar to the single turbo setup for a parallel twin-turbo on a ‘V’ shaped engine.
It requires higher cost and is somewhat complex because of the usage of doubled components.
Concern a sequential turbo or to use a turbo at low and high rpm allow for a much wider and flatter torque curve. Better low-end torque, but won’t lose power at high RPM like a smaller single turbo.There are lighter and more efficient for achieving similar results.

3. Twin-Scroll Turbo

Types of Turbocharger - Twin Scroll Turbo

These types of turbochargers need a split inlet turbine casing and exhaust manifold that individually joins the correct engine cylinder with each scroll.

Take an example, in a four-cylinder engine (with firing order 1-3-4-2), cylinders 1 and 4 can support one scroll of the turbo, while cylinders 2 and 3 feed a different scroll. This layout gives an efficient distribution of gas exhaust energy to the turbo and helps provide condensed, pure air in each cylinder.

The more energy is sent to the exhaust turbine, which means more power. Repeat, there is a major cost for approaching the complexity of a system that requires complex turbine housing, exhaust manifolds, and turbos.

Advantages of Twin-scroll TurboDisadvantages of Twin-scroll Turbo
You can get more power because more energy is sent to the exhaust turbine.
It needs a specific engine layout and exhaust design.
Based on various scroll designs, a wide RPM range of effective boosts can be possible.
These are costly and complex compared to conventional single turbos.
You can get more tuning flexibility because more valve overlap is possible without interrupting the exhaust scavenging.

4. Variable Geometry Turbo (VGT)

Variable Geometry Turbochargers are also known as variable nozzle turbines. It is commonly used in diesel engines because the exhaust gases in diesel engines are low, the heat will not harm the vanes.

Variable geometry turbo consists of a ring of vanes of aerodynamic shape in the turbine housing at the turbine inlet. It is complex in design and also requires a higher cost than other types. Now VGTs are limited due to their cost in petrol engine applications.

Because of their ability to change the area-to-radius ratio, these types of turbochargers result in a wider boost range and shorter lag times so that it matches the engine RPMs. This design allows the aspect ratio of the turbocharger to change when the position is changed.

Advantages of Variable Geometry TurboDisadvantages of Variable Geometry Turbo
They provide a wide and flat torque curve and provide effective turbocharging over a wide RPM range.
These are commonly used in diesel applications, where exhaust gases are low, so the vane is not damaged by heat.
Only one turbo is needed to simplify the sequential turbo setup.This requires a higher cost because foreign metals have to be used to maintain reliability for gasoline application.

5. Variable Twin Scroll Turbo

The variable twin-scroll turbo is a combination of twin-scroll turbo and variable geometry turbo. This turbo allows good high-end performance in any vehicle. This design provides exhaust airflow to be directed into only a single scroll.

In addition, it also provides the amount of the valve to open to allow gases to split in both scrolls if needed. The VTS turbocharger design gives a cheaper and more robust option to the VGT turbo, meaning that it is a good option for petrol engine applications.

Advantages of Variable Twin Scroll TurboDisadvantages of Variable Twin Scroll Turbo
These are cheaper than variable geometry turbo, so it allows gasoline turbocharging.
It requires a higher cost and is complex compared to a single turbo or common twin-scroll turbo.
They also provide a wide and flat torque curve.
This technique has been worked with before, but it is not sustainable in the production world.
They are more robust in design than variable geometry turbo based on material selection.

6. Electric Turbo

The electric turbos are the latest and recently added to the turbocharger industry. It is completely different from the other types of turbochargers. They are used to reduce the turbo lag and assist a normal turbocharger at low engine speeds.

This is done by attaching an electric motor that rotates the compressor from the start and through the lower revs until the power from the exhaust volume is sufficient to make the turbocharger work.

These types of turbochargers have one drawback is that it is quite expensive and complex. This turbocharger choice also allows for the consumed energy to be recovered and used to generate power.

Advantages of Electric TurboDisadvantages of Electric Turbo
Turbo lag and exhaust gases are easily eliminated by connecting an electric motor directly to the compressor wheel.
Higher costs are required and are complicated, as you must now consider the electric motor and ensure that it remains cool to prevent safety issues.
The wasted energy is recovered by connecting an electric motor to an exhaust turbine.
VGTs or twin scrolls can provide similar benefits at a significantly lower cost.
It provides a wide effective RPM range with full torque.

Why Turbocharger is Needed?

In general, engines suck air directly from the atmosphere. So, they do not suck enough air out of the atmosphere for combustion. This may be due to the high speed or the design of the engine.

In that case, you need to use an external device to provide air to the engine for entire combustion, and this device is known as a turbocharger. A turbocharger obtains energy from exhaust gases to do its work.

Applications of Turbocharger

Turbochargers were mainly employed to increase the amount of air going into the engine. And also increases the amount of fuel that can be combusted efficiently, which in turn increases power.

Power also improved by increasing the size of the engine, but this will increase the weight and internal friction, which will increase fuel consumption.

The turbocharger performs an important role in the IC engine. This increases the volumetric efficiency of the IC engine cylinder by giving it compressed air. Therefore it benefits in radiation control. So it is used in aerospace, automotive, marine, and energy sector applications.


What is Turbocharger?

A turbocharger is a part of turbine-powered forced induction, which develops an engine’s efficiency and power output by forcing more air into the combustion chamber.

What is the advantage of using a turbocharger?

By using a turbocharger in your car, the engine can provide greater power density and increased fuel efficiency to your car. Since a turbocharger allows smaller engines to give more power, manufacturers can reduce their engine displacement.

Wrapping it up

A turbocharger is attached to an engine to deliver more power. This enables smaller engines to produce more horsepower and torque than normal. It uses the heated and expelled air from the engine to rotate the compressor wheel and take the outside air.

So for now, I hope that you have learned about the different types of turbochargers. If you have any questions or doubts about this article you can ask in the comments.

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Download The PDF file of this article

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About Saif M

Saif M. is a Mechanical Engineer by profession. He completed his engineering studies in 2014 and is currently working in a large firm as Mechanical Engineer. He is also an author and editor at www.theengineerspost.com

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