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How Does a Compound Turbocharger System Work?

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Coompund Turbocharger

Coompund Turbocharger

Forced induction was the old regular system; it is a way of compressing air into the intake of a combustion engine. Compression of the air going into the engine to produce more power is called boost. Over time, in the process of finding a solution to the problem of using more fuel to get more boosting power, so many alternatives sprang up, but this article will be concentrating on the Compound Turbo Charger.

What is compound turbocharger?

There is a difference between a compound turbocharger and twin turbocharger; when you see a turbocharger engine or system that uses two compressors, then you have a twin turbocharger. The twin-turbo system is of the same size, their primary function is to compress air and at the same time splits the air into the intake that exists between the twin turbochargers. The twin turbochargers are placed parallel to each other.

The compound turbo system has two compressors, in its case the turbo system are of different sizes, unlike the twin turbo system. Their arrangement is in series, unlike that of the twin system arranged parallel to each other. Its main job is to force air into your intake manifold or intercooler, but instead of splitting, the compressors would rather work together by waiting for one to supply its own air before the other compressor takes over.

How the compound turbo works

The compound turbocharger has two compressors turbocharger, the larger one and the smaller one. The larger one is a low-pressure turbocharger, while the smaller one is a high-pressure turbocharger. This compound turbocharger follows a process to supply air into your intake intercooler. The air coming directly from the atmosphere passes through the low-pressure turbo, and moves to the high turbo before finally getting to the intake manifold or intercooler and in the process, compound the boost effect to the desired level which is its primary job.

Let’s give you a better explanation of how the two compound turbocharger works so you can understand the entire process. We all know that both water and air are fluid, now if water flows from a larger pipe to a smaller one, you should expect that the pressure of the water passing through the smaller tube will increase significantly. The same process applies to the low and high compound turbochargers; in this case, the air is flowing and not water through the turbocharger. The more the boost, the more the power per unit of fuel, and the more energy to perform better.

Compund Turbocharge Diesal Engine

Compund Turbocharge Diesal Engine

How compound turbocharger help reduce turbo lag

Before we can go deep into this topic, we need first to understand what turbo lag means before integrating it to how compound turbocharger help reduces turbo lag. Turbo lag occurs in cases when the response of the throttle is negatively affected. As a result of the inertia from spinning components that comes up within a turbocharger. Usually, there used to be a delay because of the depression that occurs between the accelerator pedal and the extra boost power received from the turbocharger; all turbochargers are guilty of this delay and the bigger the turbocharger, the more the turbo lag. Now that it is understandable that there is no way we can fully overcome turbo lag in a turbocharger system, we can still have a device that can make the throttle response almost instantaneous.

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Based on research and findings, reducing the turbo lag now seem to be the best attribute available as a means of addressing the problem of a compound turbocharger. For example, if you add two small high-pressure turbochargers together, the lower end of the RPM range will get an undenied boost, and there won't be a delay between the time the accelerator is depressed, and the time accelerator is applied. As the pressure comes from the accelerator, the high-pressure turbo will continue to supply the boost to your intake valve until enough exhaust is produced to spool the turbo with the low-pressure. The moment the low-pressure turbo starts to spool, the amount of boost that passes through the intake will automatically increase.

Let give another example so you can get a clear picture of what I am trying to explain in detail. The use of water as a means of explanation seems to be giving a better understanding. Based on the last example I made using water, the explanation that when water flows freely from a more significant passage to a smaller one, the pressure on the lower pipe will automatically increase. Now if you can imagine as water moves from the larger tube to the smaller ones and it now gets to the smaller pipe that already has a smooth running flow of water, the pressure automatically increases and enables a good flow. That explains the real picture of how the compound turbo system works. The level at which it can give a boot is exceptionally great.

A useful and well-designed turbocharger compound gives you nothing but everything you need of a turbo setup having not to worry about any of the normal turbo drawbacks. A sound compound turbocharger system provides room for an excellent throttle response as it also allows a dramatic increase in the performance levels and a fun loving time in the driver’s seat. The only drawback that you can find in a compound turbocharger system is the design which can result in headaches when you are at the point of turning on the fuel and ignition maps.

Building a turbo charger differs from one designer to the other; as technology continues to advance more companies tends to look for an alternative to their existing ways of developing their turbo charge that is what makes compound turbocharger relevant in the automobile industry.


Larry Slawson from North Carolina on July 30, 2019:

Very interesting! Thanks for sharing!

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