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Beginner's Guide: What Are the Different Types of Turbochargers? 

November 16, 2022  -  Power Adders

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Turbochargers are a great way to increase power in a combustion engine. Several setups can be employed to create more power, from a single turbo to twin and compound turbos. But what are the different types of turbochargers, and how do they work?

JEGS created the ultimate beginner's guide to help make sense of it. First, a turbocharger takes exhaust gas and channels it into the turbine wheel. This wheel is connected to the compressor wheel, which pressurizes the air intake. The compressed air, known as boost, is forced into the engine. The result is increased power output while keeping the overall engine displacement the same.

Single Turbo

A single turbo is the most basic and most common type of turbocharger. It is typically found in both gas and diesel vehicle applications. In a single turbo setup, exhaust gases from all cylinders are routed through a single turbocharger.

The single turbo is the simplest and most cost-effective option. However, it does have some drawbacks. One such drawback is that the single turbo can cause turbo lag. In particular, diesel turbos can experience significant lag as a single turbo has a limited powerband where it can generate boost.

Twin-Turbo

As the name suggests, twin-turbos means adding a second turbocharger to an engine. This setup is generally used on bigger engines such as V6s and V8s. Each cylinder bank has a turbocharger assigned to it.

Another way twin turbos can be used is to have both turbos working in sequence. The smaller turbocharger spools up first and provides boost until the engine reaches a certain rpm. At this point, the second, larger turbocharger starts providing boost. This setup is known as staged or sequential twin-turbos.

The main advantage of a twin turbo engine is that it can produce significant power without sacrificing low-end torque. Twin turbos also help to reduce turbo lag as each turbocharger is only responsible for half the cylinders.

Twin-Scroll Turbo

Compared to a basic turbocharger, the twin-scroll turbo is more efficient. In a twin-scroll turbo, the exhaust gases from each cylinder are routed into two separate channels. These channels converge into a single turbine inlet, but the exhaust pulses are kept separated. This separation helps to improve spool-up time as well as overall efficiency.

As a result, a twin-scroll turbo provides more power while being more efficient. Essentially, it produces a boost on a wider powerband compared to a simple turbocharger. This makes twin-scroll turbos ideal for smaller engines that need to generate a lot of power throughout the entire rev range.

Variable Twin Scroll Turbo

Variable twin-scroll turbos combine the best of both worlds. Using features from a variable geometry turbo and twin-scroll turbo gives, a variable twin-scroll turbo provides boost across the entire powerband while also being highly efficient.

The twin-scroll turbo uses a system of vanes to direct exhaust gases into either one or two turbine inlets. At low engine speeds, all the exhaust gases are routed into a single inlet to help improve spool-up time. As engine speed increases, the vanes start to direct more exhaust gases into the second turbine inlet. This system is known as a variable turbine geometry (VTG) system.

The result is a turbocharger that can boost all engine speeds without sacrificing power or efficiency. This makes the variable twin-scroll turbo ideal for high-performance applications. Nowadays, variable twin-scroll turbos are becoming commonplace on many new engines.

Variable Geometry Turbo

Variable geometry turbochargers feature a ring of aerodynamically shaped vanes at the turbine inlet. Internal vanes change the area-to-radius (A/R) ratio of the turbos to match the engine's RPM, giving peak performance. A low A/R ratio allows the turbo to rapidly spool up by increasing exhaust gas velocity at low RPM. At higher revs, the A/R ratio increases, allowing for greater airflow. This implies a reduced boost threshold that cuts turbo lag and creates a wide and smooth torque curve.

VGTs are commonly used in diesel engines where exhaust gases are at lower temperatures. Still, they have been limited in gasoline engine applications due to their cost and the requirement for components to be made from heat-resistant materials. The vanes must be made from these expensive materials to prevent damage from the high temperatures of exhaust gases.

As a result, current variable geometry turbochargers in gas engines are only reserved for high-end, high-performance luxury cars due to their high manufacturing cost. Luckily, VGTs are becoming commonplace on many new gasoline engines as technology advances.

Electric Turbo

Lastly, electric turbochargers are a new type of turbocharger that is slowly making its way into the automotive market. As the name suggests, electric turbochargers feature an electric motor to eliminate lag associated with boost lag found on conventional turbos.

The main advantage of an electric turbocharger is that it can provide instant acceleration at any RPM and speed. Spinning up the compressor wheel to its optimum speed before exhaust gases produce pressure on the hot side means no delay in boost pressure. The result is smoother power delivery and reduced turbo lag.

Electric turbochargers are still in their infancy, so they are only found on a handful of production vehicles. As electric turbochargers become more refined, we will likely see them become more commonplace in the future.

Now that you know the different types of turbochargers, it's time to choose the right one for your application. Remember that twin-scroll and electric turbochargers are best suited for high-performance applications, while variable geometry turbos offer the best balance of performance and efficiency. Whatever setup you go for, choosing an appropriate size is crucial. 

For example, larger twin turbo engine turbo sizes may not be suitable for a smaller engine, whereas a small turbo may not provide great top-end power.

JEGS is here to help you choose the right turbocharger for your application. We offer a wide selection of turbos from the top brands in the business. Contact our tech support team for more information on choosing the best turbocharger for your engine.

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