If you have been looking for the perfect, high performance car, you may have noticed the word turbo being thrown around by manufacturers. Most high-performance BMWs have Twin power which should not be confused with Twin turbo. In order to understand what a turbo charger is let alone how it works; we need to explain how a car engine works.
How a car engine works.
There are very many types of engines including steam engines but for the sake of this article we are going to discuss about internal combustion engines which are used in modern cars today. It basically works on the principle of burning fuel to produce energy in order to propel your vehicle. This process occurs in four stages as illustrated below.
Because of these four processes, this engine is referred to as a four stroke engine. The process kick starts with the intake of air to the engine. Air is essential for combustion to occur.
Four Stroke Cycle.
The cycle starts with the pistons in the cylinder moving downwards. During this process the intake valve is open while the exhaust valve is closed. This creates a partial vacuum which draws in a mixture of air and fuel.
Once the two have been drawn into the cylinder, the piston moves upwards while the exhaust valve and the intake valve is closed. This is called the compression stage. The air fuel mixture is compressed and the purpose of this is to raise the temperature of the mixture and keep it at constant ignition point.
Once the mixture has been compressed, the spark plugs ignites the mixture causing an explosion, producing enough force to push the piston downwards which in turn rotates the crankshaft propelling the car forward.
At this point both the intake valve and the exhaust valve are closed. The piston moves upwards due to the momentum gained and the exhaust valve is opened while the intake valve remains shut for the exhaust gases to move out of the cylinder straight to the tail pipe and out.
The process is repeated many times to keep the car going. That is how a car engine basically works. Below is a visual representation and summary of how a four stroke internal combustion engine works.
Let’s get to the good part……….Turbo Chargers.
Now that we have a basic understanding of how a four stroke internal combustion engine works, let’s dive deeper into what a Turbo charger is and how it works.
But first, let’s take a history lesson. Back in the late 19th century the internal combustion engine was well known and in use but there was one problem. Each time engineers wanted to make a car faster, they had to increase the displacement of the cylinders eventually increasing the size of the engine.
The sole reason for this was to draw in more air-fuel mixture for more combustion to occur. As they increased the engine size, the mass of the car also increased hence making the vehicle heavier and relatively inefficient.
In 1905, a Swiss engineer by the name Alfred Buchi discovered that you could increase the total power output of an engine by reusing the exhaust gases.
Remember the fourth stage of the four stroke internal combustion engine; the exhaust stage? Well those exhaust gases are the ones we are talking about. Basically, the system that reuses exhaust gases from the four stroke cycle to generate more power is known as a turbo charger.
Working principle of a Turbo charged engine.
In more technical terms, the turbo charger is a system that is mainly comprised of a turbine and an air compressor which harnesses the waste exhaust gases and uses it to produce more power for the engine.
After the fourth stage of the four stroke cycle, the exhaust gases are used to run a turbine which is part of the turbo charger. The turbine in turn pushes the exhaust gases to the compressor. The exhaust gases spin the turbine to speeds of up to 280,000RPM which is nuts if you pause and think about it. The compressor increases the compression of air making it denser. Since there is a lot of heat produced, the turbo charger is fitted with an inter-cooler which sits in between the turbo and the engine. The inter-cooler is basically made up of cooling fins which aids in dissipating heat away from the engine.
The scoop on top of most Subaru vehicles fitted with a turbo charger provides cool air for the inter-cooler. Once the air is cooled, it becomes even more dense which is in turn conveyed to the engine.
The more the air, the more rapid the fuel burns. That is how a turbo charger works. This concept helped reduce engine sizes while outputting more power. Turbo chargers are mainly used in high performance vehicles and have proved to be really efficient. But due to the insatiable nature of human beings we needed more power. One way of doing this, is by increasing the turbo charger size but this has proved to be very inefficient.
In fact, the main challenge to a larger turbo charger is an effect known as lag. Turbo lag is the period between when the driver presses the accelerator and the time the turbo charger kicks in to provide the extra boost which is greatly increased by a larger Turbo.
This is where Twin Turbo comes in. Twin turbo is basically two turbos in one engine and their placement varies. It can either be a parallel twin turbo, a sequential twin turbo or a two stage twin turbo. Each has it’s own advantages and disadvantages but we are not going to dive into them in this article.The purpose of a twin turbo is to produce more power without increasing the size of the turbo charger. One of the earliest adopters of this concept is the Maserati Bi-turbo in 1981.
Two turbos are very efficient especially in V shaped engines as each can be placed on opposite directions producing more power for the engine.
Advantages of having a turbo charged engine.
- Less Carbon(IV)oxide is produced to the atmosphere.
- Up to 40% less fuel is used in diesel engine.
- Up to 20% less fuel is used in gasoline engines.
- The exhaust gases are not wasted as they are reused.
- More performance.
