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The Basics of Variable Geometry Turbochargers

The Basics of Variable Geometry Turbochargers

To better understand turbochargers as a whole, we have provided you with some additional information below on the Variable Geometry Turbocharger (VGT). Being able to better comprehend the basics of variable geometry turbochargers will allow you to get a stronger grasp on the product itself and why it differs from the fixed geometry turbocharger. Don’t let it overwhelm you! Instead, continue reading the information to get even more educated and to ensure that your turbocharger is the right fit for your car and that it is working at its full capacity. Before you know it, you will be a turbocharger expert!

The Basics

Understanding the basic science that allows the turbocharger to work will be extremely beneficial. A good starting point is understanding that there is a mismatch between the exhaust flow of the internal combustion engine and the radial flow of the turbocharger. This is because of the geometry and different speed range operation. For a further explanation to help you better understand, the turbocharger will work poorly if the flow area (geometry) is designed to match the speed and load of the engine at low and medium speeds. On the other hand, matching the geometry of the turbine for a fast response will allow for the engine to operate at high speed, causing the turbocharger to take in air pressure that could exceed the limit.

While this may be somewhat confusing, basically all you need to understand is that finding the right balance is key.

Turbocharger A/R Ratio

This is a very important characteristic of the turbocharger. The ‘A’ stands for the turbine/compressor inlet area, while the ‘R’ stands for the radius of the turbo centerline. The importance of this specific characteristic is that the flow capacity of the turbine depends on this ratio, thus having a significant impact on the overall performance of the turbocharger itself.

To better understand this specific element of the turbocharger, it is important to know that the small A/R ratio will increase the speed of the exhaust, resulting in the compressor to spin faster and the air intake boost to increase. Conversely, the large A/R ratio will improve the flow capacity and reduce backpressure in the exhaust manifold. Overall, VGTs combine the benefits of both the small and large ratios and allow for both advantages.

Elements VGTs Are Designed To Do

Overall, there are a few different goals or elements that the VGTs are designed to complete. Some of these include increasing the intake air boost pressure at low engine speed, preventing high-speed engines from over-boosting, thus improving fuel economy. They are also designed to reduce exhaust gas emissions, improve the response time of the turbocharger during the transient engine operation phases, and increase the availability of the engine torque. These different designs are greatly beneficial to the turbocharger world!

Types of VGTs

Pivoting Vanes is one of the most widely used VGTs in passenger vehicles. It is most common and most frequently used in diesel vehicles as well. An additional type of VGT is the Moving Wall. This is referred to by this name because the cross-sectional area of this specific VGT is located between the moving wall and the turbine casing. In many cases, the Moving Wall is designed to be used in diesel commercial vehicles. The Sliding Ring is another type of VGT and is very similar to the Moving Wall design, the only difference being that the vanes are fixed in a static nozzle plate. And the last variation of VGTs is the Variable Area. This is a very complicated and expensive mechanical system. However, it has been said that even though it is a higher cost and more complex, it still allows for a faster response time.

This brief explanation of the four Types of VGTs allows you to build a foundation in understanding the differences between them.

Advantages and Benefits

When comparing the VGT to the fixed geometry turbocharger, you can see that the VGT has numerous benefits and advantages that come with it. Not only does the overall engine braking performance improve, but a higher air-fuel ratio at a low engine speed can happen, which reduces and decreases overall exhaust gas emissions. Two additional benefits are that using the VGT improves the overall exhaust gas recirculation rate and that the torque curve of the engine improves the control of the air-fuel ratio. Don’t these benefits sound like the VGT really does make a difference?

Things To Keep in Mind

When educating yourself on turbochargers, it is important to keep many different elements in mind. The first being that they can be very confusing, and that is okay! Not only are there different kinds of turbochargers out there, but there are also so many different elements that play a role in selecting the right one. An example of this is that VGTs are not always even referred to as VGTs. Different manufacturers refer to these parts in different ways. Because of the complexity, it is never a bad idea that you consult a professional mechanic regarding turbochargers to better understand and educate yourself.

Looking at this article that covers the basics of variable geometry turbochargers will only help you further understand the different turbochargers out there. The information above including the A/R ratio, what it is specifically designed to do, the multiple types of VGTs, the benefits of the product compared to the similar ones, as well as the idea that it is okay to admit that turbochargers can be complicated is all beneficial and helpful material. You are in a better place now than you were when you began reading this article!

And to be in an even better place, reach out to us here at TurboTurbos! Not only do we have turbochargers for sale, but we have many other additional items like the Mitsubishi turbocharger for sale. In addition to our large variety of turbocharger-related products, we also have a very educated and professional staff that is available to assist you with whatever you need. All you have to do is give us a call or visit our website!

The Basics of Variable Geometry Turbochargers


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