If you’re a car enthusiast or have friends that are into cars, you may have heard a lot about turbos. Generally, people don’t know much about turbos or how they work and have many misconceptions about them. Well, you don’t have to worry if you don’t know much because we’re going to cover all the basics about turbochargers in this article. Simply put, turbochargers (or simply turbos) are used to boost up the amount of horsepower an engine produces. Let’s dig in and see how they work, where they are used, and how many types are there.
A turbocharger works like a mechanically driven exhaust device that boosts the power of the engine by pumping in more air for it to burn. This is done by using a pair of fan-like castings which are mounted on a common shaft. One which is usually known as the turbine is connected to the exhaust via a pipe, while the other known as the compressor is piped to the engine intake. The flow of air into the exhaust pipe spins the turbine which causes the compressor to turn and blow air into the engine at a greater rate on which it can’t originally pull on its own. This increased amount of air is mixed with a greater volume of fuel, thus increasing the combustion in the engine and results in more output power.
In order, to make the turbo work properly there’s a minimum amount of pressure that needs to be exerted on the exhaust to make it spin, this minimum pressure is reached around an rpm of 2000-3000. The time required by the engine to reach this rpm is known as ‘Turbo lag’. But once the turbo starts working the resultant is pure muscular power.
Initially, turbochargers were used in massive engines like those of ships, trains, and aircrafts. When cars became common and automotive sports was on the rise, the competition amongst the manufacturers led them to fit turbos in their sportscars so they could produce more horsepower. But, now after the updated governmental policies on higher fuel economy standards; many automobile manufacturers have switched to small-sized turbo engines in place of huge less fuel-efficient ones. The turbocharger engines usually use high octane fuel as they have direct fuel injection, this allows the use of cheap 87-octane.
Another important use of turbochargers is in the diesel engines. A diesel engine uses a turbocharger to have an extra boost at higher rpms. This makes diesel engines more fuel efficient for passenger cars.
The six most commonly used turbochargers are:
A single turbocharger is the simplest of all turbochargers. It uses the simplest setup and because of this it is relatively cheap and is the most common type of turbo in use. You can either use a small low-end turbo producing low down torque on less rpm or you can opt for top-end one which produces massive power.
This turbocharger is actually a combination of two single turbochargers. This gives you the advantage of having the choice of both low-end turbo and a high-end one. The sequential turbo enables you to enjoy the early torque kick of a small turbo as well as massive power from the high-end turbo. But this turbocharger is expensive, heavy and complex to build.
You must be familiar with the working of turbochargers; a turbocharger redirects air towards the engine. There are gaps in between where no air enters into the engine and these gaps interfere with the powering laps. This problem can be solved by using a twin-scroll turbo as it uses a divided inlet turbine housing with a specific exhaust manifold which pairs the right cylinders to each scroll. As a result, there’s less pulse overlap and less lag.
This type of turbo is an expensive and complex one but is a popular power solution for diesel engines. A VGT (Variable Geometry Turbo) has a ring of aerodynamically shaped vanes in the turbine housing that can alter their area-to-radius ratio to match the rpm. At low rpm, more velocity and pressure are created to enhance the turbo effect whereas at higher rpm more air is allowed to enter which increases the boost range and decreases the lag.
This turbocharger is the combination of a VGT and a twin-scroll turbo. It works in such-a-way that at lower rpm one of the scrolls is completely closed, this forces the air into the other scroll and results in a good turbo response. With the increase in speed, more air is allowed to enter other scrolls resulting in high-end performance.
They are the latest turbochargers. They have electric compressors which provide an instant boost to the engine until the turbocharger is spooled up. These turbochargers are very complex and expensive. This system is used in Audi SQ7. Another example is the BorgWarner’s eBooster.
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