Turbochargers. Also known as turbos for short. What are they? How do they work? I am going to explain in this blog post.
To make things simple, let me give a background. In an internal combustion engine, if you want to make more power from the same engine, then you need to use different methods of forced induction. Forced induction means to push more air into the engine forcefully. Now, an engine needs air to burn the air-fuel mixture and produce power. So, if you push more air into the engine forcefully, you can produce more power. One of the methods in order to push more air in the engine to produce more power is through turbocharging. So, what happens is, a turbo sucks in air through the exhaust, then force-feeds the engine more air than what it would get through its standard intake. It is a small turbine that sits between the engine and the exhaust. A turbocharger consists of four parts. The turbocharger, intercooler, Wastegate and ECU tune. The turbocharger is the main turbine that spins. It looks like a snail. It features and air intake, an exhaust intake, two different impellers (A turbine in the rear and compressor toward the front), and a charged air exhaust that goes to the intercooler. There’s also a hose line for oil. The second part is the intercooler, which is used to cool the charged air forced out of the turbocharger, a secondary radiator, or intercooler, intercepts the air before it reaches the engine. It uses the coolant as a chilling agent. The third part is the wastegate, it is a valve in between the exhaust intake and the turbocharger that by passes the turbine to control the boost pressure. The fourth part is the ECU tune. The ECU is the Engine Control Unit. It is the engine’s electronic brain. It needs to be calibrated differently for fuel-to-fuel air mixtures and ignition timing for supporting the turbocharger. When you add a turbocharger to an engine which originally does not have it, you need to reprogram the ECU in order for it to function properly.
Anyways, now that you know what is a turbocharger and how it works, you need to know the types of turbochargers. The types are as follows-
Single turbos-Single turbochargers are the simplest type of turbochargers. They just include one single turbo. They differ in size and power. There are small and big turbos. Large turbos provide higher levels of top end power, while small turbos can spool faster and provide better low-end power. They are a cost-effective way for increasing power and efficiency. They have become immensely popular because of that. They can allow smaller engines to produce more power, power equivalent to engines with larger displacement. The downside to this is that you might experience some sort of “turbo-lag” until the turbo starts to operate within its peak rev band.
Twin-turbo-As the name implies, you put two turbos of same size in the engine, instead of just one. You might see this layout in many high-end, performance-oriented production cars. Putting two turbos in an engine can increase the total power and efficiency of the engine. It can also reduce turbo lag, if you use twin sequential turbocharging, in which one turbo can be used for lower RPMs and another can be used for higher RPMs. But, having two turbos increases complexity of the engine and also the cost.
Electric turbochargers- This smart and advanced technology of turbocharging has been already used in Formula 1 cars and is still used in them. This type of turbo makes turbo lag a thing of the past. This technology involves a turbo working in sync with an electric motor. When there are not enough exhaust gases, you can spin the turbo using the electric motor. This provides smooth power delivery and low-end torque without any turbo lag. Also, it provides a very effective RPM range with even torque throughout. Also, by connecting an electric motor to the exhaust turbine, wasted energy can be recovered, which is done in Formula 1. However, as good as this option sounds, as complex and costly it is. Formula 1 cars are expensive anyway so they don’t care if their turbocharging technology is expensive.
Variable Geometry Turbocharger (VGT)-VGTs include 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 the cross-sectional area. These internal vanes alter the turbos area-to-radius (A/R) ratio to match the engine’s RPM, and so give peak performance. At low RPM, a low A/R ratio allows the turbo to quickly spool up by increasing exhaust gas velocity and at higher revs the A/R ratio increases, thereby allowing increased airflow. This results in a low boost threshold reducing turbo lag, and provides a wide and smooth torque band. VGTs are in limited use in petrol engines because of 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 restricted their use to applications within luxury, high performance engines.
Variable Twin-Scroll Turbochargers (VTS)-As the name suggests, a VTS turbocharger combines the advantages of a twin-scroll turbo and a variable geometry turbo. It does this by the use of a valve which can redirect the exhaust airflow to just a single scroll, or by varying the amount the valve opens can allow for the exhaust gases to split to both scrolls. The VTS turbocharger design provides a cheaper and more robust alternative to VGT turbos, meaning it a viable option for petrol engine applications.
Twin-Scroll Turbo-Twin-scroll turbochargers require a divided-inlet turbine housing and exhaust manifold that pairs the correct engine cylinders with each scroll, independently. For example, in a four-cylinder engine (with a firing order 1-3-4-2), cylinders 1 and 4 might feed to one scroll of the turbo, while cylinders 2 and 3 feed to a separate scroll. This layout provides more efficient delivery of exhaust gas energy to the turbo, and results and helps provide denser, purer air into each cylinder. More energy is sent to the exhaust turbine, meaning more power. Again, there is a cost penalty for addressing the complexity of a system requiring complicated turbine housings, exhaust manifolds and turbos.
So, this is what turbochargers are, and how they work. I have also explained what are the types of turbochargers. So now you might be convinced that turbocharging is an efficient way to increase the power of the engine. Single turbo is one way to do it cost-effectively, as mentioned above.
Thank you for reading my blog!!
