What is a Turbocharger?
A turbocharger is a device fitted to a vehicle’s engine that is designed to improve overall efficiency and increase performance. For this reason, many automakers choose to turbocharge their vehicles.
A turbocharger, formerly a turbo-supercharger and colloquially known as a turbo, is a turbine-driven forced induction device that increases the power output of an internal combustion engine by forcing additional compressed air into the combustion chamber.
This improvement over the power output of a naturally aspirated engine is because the compressor can force more air and proportionally more fuel into the combustion chamber than atmospheric pressure alone.
A key difference between a turbocharged diesel engine and a traditional naturally aspirated petrol engine is that the air entering a diesel engine is compressed before the fuel is injected. Here the turbocharger is crucial for the performance and efficiency of the diesel engine.
It is the turbocharger’s job to compress more air entering the engine’s cylinder. When air is compressed, the oxygen molecules pack more tightly together. This increase in airflow means more fuel can be added to a naturally aspirated engine of the same size.
This then produces increased mechanical power and an improvement in the overall efficiency of the combustion process. Therefore, engine size can be reduced for a turbocharged engine, resulting in better packaging, weight savings benefits, and overall improved fuel economy.
Who Invented the Turbocharger?
A Swiss engineer named Alfred Buchi first developed the turbocharger design in 1905 to increase the performance of diesel engines. Neat!
How Much Extra Power Can You Get?
This is the question of any transmission, and unfortunately, there is no easy answer. A normal turbocharger provides network enthusiasts around 20 to 40 percent more power than standard products.
How much extra power, however, depends on a variety of variables including how big or small the turbocharger is, what changes you’ve made to the internal parts of the engine, what type of fuel you’re using, and what ECU your turbocharger setup used. Your car’s profits will vary.
How Does A Turbocharger Work?
A turbo is made up of two halves joined together by a shaft. On one side, hot exhaust gases spin the turbine, which is connected to another turbine that draws in air and compresses it into the engine. This compression gives the engine that extra power and efficiency because the more air that can get into the combustion chamber, the more fuel that can be added for more power.
A turbocharger is made up of two main parts: the turbine and the compressor. The turbine consists of the turbine wheel and the turbine housing. The turbine housing has the task of conducting the exhaust gas into the turbine wheel.
The energy from the exhaust gas turns the turbine wheel and the gas then exits the turbine housing through an exhaust outlet area.
The compressor also consists of two parts: the compressor wheel and the compressor housing. The compressor mode of action is the opposite way of the turbine.
The compressor wheel is attached to the turbine by a forged steel shaft, and when the turbine rotates the compressor wheel, the high-speed rotation draws in air and compresses it.
The compressor housing then converts the high velocity, low-pressure airflow into a high pressure, low-velocity airflow through a process called diffusion. The compressed air is forced into the engine, allowing the engine to burn more fuel to produce more power.
Parts of a turbocharger
1. The Turbine
The turbocharger turbine, which consists of a turbine wheel and a turbine housing, converts the engine exhaust gas into mechanical energy to drive the compressor. This pressure drop is converted into kinetic energy by the turbine to drive the turbine wheel. There are two main types of turbines: axial and radial flow.
The turbocharger bearing system looks simple, but it plays a key role in a number of critical functions. Some of the most important are controlling the radial and axial movement of the shaft and wheels and minimizing friction losses in the bearing system.
3. The Compressor
Compressor wheels are one of the most discussed parts of a turbocharger. The compressor section, like the turbine, consists of two main components: the compressor wheel and the compressor cover. The job of the compressor is to literally compress fresh air and direct it to the throttle body.
4. Center Housing/Rotating Assembly (CHRA)
The CHRA may not run out of ink, but it is one of the most critical parts of any turbocharger assembly. In practice, the CHRA serves as the mounting point for both housings and must be made of an essential material to handle the heat and stress on the turbine.
Understanding that a turbocharger compresses air makes it easy to see why an intercooler is important. Without doing too much math (we’re talking about the ideal gas law again), let’s just say that as pressure increases, heat is generated within a set volume.
A wastegate is simply a device that bleeds off exhaust gas before it reaches the inlet of the turbine housing.
7. Blow-Off Valves
A relief valve is essentially a pressure relief valve that is mounted on the compressor side of a turbo system. Its job is literally to release the excess boost pressure trapped in the system when the throttle blade closes.
8. Piping and Manifolds
Piping is perhaps the last thing most fans consider when building a turbo system. However, proper application and sizing are essential to ensure optimal performance. In a typical turbocharger system, the piping can be divided into three distinct sections: the manifolds, the hot side and the cold side.
Turbo manifolds, dealing with extreme temperature changes, incredible backpressure, and high loads make these areas one of the most likely areas in a turbo system to experience problems. To understand the extremes a variety must endure day in and day out, it is best to develop a variety based on longevity and strength, even if it means giving up a little bit of performance.
9. Hot Side Piping
Any piping related to the movement of the actual exhaust gas, be it to or from the turbocharger, is typically referred to as hot side piping. Due to the extreme heat generated when exhaust gases are transferred to the turbine casing, it is important to use a strong material here, and stainless steel is the material of choice for many manufacturers.
10. Cold Side Piping
The “cold side” of a turbo kit refers to any piping related to moving compressed air from the turbocharger to the throttle body. If you are installing an intercooler, it is also part of the cold side and will need to be plumbed correctly to make everything work.
Types of turbocharger
There are a number of different types of turbochargers used within the automotive industry:
- Twin-Scroll Turbo
- Variable Geometry Turbo
- Variable Twin Scroll Turbo
- Electric Turbo
Single turbochargers are what most people consider turbos. Due to the different sizes of the elements in the turbo, completely different torque properties can be achieved. Large turbos provide a higher level of top-end power, while smaller turbos can spool faster and provide better low-end power.
They are an inexpensive way to increase engine power and efficiency, and as a result, they are becoming increasingly popular. They enable smaller engines to increase efficiency by producing the same power as larger, naturally aspirated engines with less weight.
However, they typically work best in a narrow RPM range and drivers often experience “turbo lag” until the turbo begins to operate within its peak RPM range.
As the name suggests, twin turbos mean adding a second turbocharger to an engine. For V6 or V8 engines, this can be done by assigning a single turbo to each cylinder bank.
Alternatively, a smaller turbo could be used at low speeds with a larger turbo for higher speeds. This second configuration (known as double sequential turbocharging) allows for a wider speed range and provides better torque at low speeds (reducing turbo lag), but also provides power at high speeds. Unsurprisingly, having two turbos adds significant complexity and associated cost.
3. Twin-Scroll Turbo
Twin scroll turbochargers require a turbine housing with a split inlet and exhaust manifold that couple the correct engine cylinders to each scroll. independently. For example, in a four-cylinder engine (with a 1-3-4-2 firing order) cylinders 1 and 4 can be fed to one scroll of the turbo, while cylinders 2 and 3 are fed to a separate scroll.
This arrangement allows exhaust energy to be delivered to the turbo more efficiently and results in denser and cleaner air in each cylinder. More energy is sent to the exhaust turbine, which means more power. Again, there is a cost penalty for dealing with the complexity of a system that requires intricate turbine housings, exhaust manifolds, and turbos.
4. Variable Geometry Turbocharger (VGT)
Typically, VGTs contain a ring of aerodynamically shaped vanes in the turbine housing at the turbine inlet. In turbos for passenger cars and light commercial vehicles, these vanes rotate to vary the gas swirl angle and cross-sectional area.
These internal vanes change the turbo area to radius (A / R) ratio to match engine speed, providing top performance. At low RPM, a low A/R ratio allows the turbo to spool up quickly by increasing the exhaust speed. At higher speeds, the A/R ratio increases, allowing increased airflow. This results in a low charge threshold which reduces turbo lag and provides a wide and even torque band.
While VGTs are typically used in diesel engines where exhaust gases are at a lower temperature until now VGTs have been limited in petrol engine applications due to their cost and the requirement for components to be made from exotic materials.
The high temperature of the exhaust gases means that the vanes must be made from exotic heat-resistant materials to prevent damage. This has limited their use to luxury high-performance engine applications.
5. Variable Twin-Scroll Turbocharger (VTS)
As the name suggests, a VTS turbocharger combines the advantages of a twin-scroll turbo and a turbo with variable geometry. This is done by using a valve that can divert the flow of exhaust air onto only one scroll, or by varying the amount the valve is opened, the exhaust gases can be split into both scrolls.
The VTS turbocharger design offers a cheaper and more robust alternative to VGT turbos, which means it is a viable option for petrol engine applications.
6. Electric Turbochargers
An electric turbocharger is used to eliminate turbo lag and to assist a normal turbocharger at lower engine speeds where a traditional turbocharger is not most efficient. This is achieved by adding an electric motor that rotates the turbo’s compressor from the start and through the lower speeds until the power from the exhaust volume is high enough to run the turbo.
This approach makes turbo lag a thing of the past and significantly increases the speed range in which the turbo works efficiently. So far, so good. It seems that electronic turbos are the answer to all of the negative characteristics of traditional turbochargers, but there are some drawbacks.
Most are about cost and complexity, as the electric motor needs to be accommodated and powered, plus also cooled to prevent reliability issues.
Advantages of Turbocharger
In addition to the extra power, turbochargers are sometimes referred to as devices that offer “free power” because, unlike a supercharger, they don’t need the power of the engine to drive it.
The hot and expanding gases exiting the engine drive a turbocharger so that the engine’s net power is not lost.
Turbocharged engines are also not affected in the same way as naturally aspirated engines when operating at higher altitudes. The higher a naturally aspirated engine climbs, the more difficult it becomes to get oxygen due to the thinning atmosphere.
A turbocharger gets around this problem by forcing oxygen into the engine’s combustion chamber, sometimes at twice the pressure of the atmosphere.
Turbochargers also improve a vehicle’s fuel efficiency, however, there is a misconception when it comes to turbocharged vehicles and fuel efficiency. Taking a naturally aspirated engine and slapping a turbocharger on top of it isn’t going to improve fuel efficiency.
Disadvantages of Turbocharger
Turbochargers have two main disadvantages compared to a naturally aspirated or supercharged engine. The first is heated. Because a turbo is powered by hot exhaust gases, it gets very hot.
Sometimes under certain engine conditions, the turbocharger itself can start glowing red, but of course, this doesn’t happen in everyday driving conditions; It happens when the engine is pushed to its limits for a continuous period of time.
This is why you see some turbocharged sports cars with vents in the hood or on the side to try to move air through the engine bay and keep things cool.
The other major disadvantage of a turbocharger is the so-called turbo lag. Under certain conditions, whenever you step on the gas, there’s a lag between the moment you request power from the engine and the moment you actually feel it.
That’s turbo lag. When the engine speed is low, not many exhaust gases flow through the turbocharger. So, when you demand power from the engine, the turbocharger turbine needs time to spin at optimal speed.
The effects of this can be lessened by downshifting to a lower gear, but enthusiastic drivers can still sometimes notice the split lag as a response.