What is meant by turbo lag? Turbocharger and its working

Turbo lag is a term that is often heard in reviews of diesel vehicles. What does it mean? The turbocharger is a device used to enhance the performance of diesel vehicles, how does it work? 

We know that an engine produces maximum energy when it burns maximum fuel. It is not enough to bring maximum fuel to the engine for this, the fuel will burn completely only if there is air in proportion to it.

The stoichiometric ratio is the minimum amount of air-fuel ratio required for fuel to burning completely. For petrol, it is 14: 1, which means 14 kg of air is required for 1 kg of petrol to burn completely.


When the required air does not reach the engine, the fuel does not burn completely and the engine emits black smoke.

Thus, to increase the power of an engine, more fuel has to be burned. It is not enough to supply more fuel to the engine, it is also necessary to supply enough air to burn completely. Only when the fuel is completely burned can the maximum energy of the fuel be utilized.

There are two main ways we can get more air into the engine.

1. Increase the bore diameter: That is, increase the cylinder size of the engine. By increasing the engine cylinder size in this way more air can be drawn into the engine. But this is not practically possible because a lot of space is required here.

Also, as the cylinder size increases, so does the size of the engine, which increases the overall weight of the engine. This adversely affects the mileage of the vehicle.

2. Pump air into the engine: The second method is to pump air with the help of a fan or blower without changing the size of the engine. That is, the air is pumped into the engine with the help of an external device, this is called charging.

This way more air enters the engine, so more fuel can be burned. This increases the performance and efficiency of the engine.

In the early stages, electric motors were used for this process. But it was powered by the vehicle's battery, So it was not very efficient.

Thus, exhaust gas comes to the fore when looking for an alternative. It contains pressure, velocity, and temperature, which means it contains energy.

It was realized that if the charging process could be done using the energy from the exhaust gas, it would make the engine efficient and powerful.

This conclusion led to the invention of the forced induction device turbocharger. With the help of this turbocharger, air can be pumped into the engine.

How a turbocharger works? 

A turbine, impeller(Compressor), and shaft are the main components of a turbocharger. The fan impeller and turbine are connected using this shaft, they are arranged in such a way that the impeller rotates as the turbine rotates.

The turbine is placed in the path of the exhaust gas so that the turbine rotates with the energy of the exhaust gas. When the turbine rotates, the impeller rotates on the other side because they are connected by the shaft. Thus the rotation of this impeller pushes air into the engine.

This is the process that takes place on a turbocharger.

Thus burning more fuel produces more smoke, which speeds up the turbine spin. The faster the turbine rotates, the faster the impeller rotates. This causes more air to enter the engine, which makes the engine more powerful.

What is turbo lag? 

Suppose you start a vehicle and start driving now. Initially, the amount of fuel burning in the engine will be less and therefore the exhaust gas will also be less. So the turbine rotates slowly, so the fan also rotates slowly.

This reduces the amount of air coming into the engine. This time more fuel gets into the engine when we press the accelerator pedal. But the air needed to burn this fuel completely does not reach the engine.  Therefore, the vehicle is not responding as intended by the driver at this time.

This condition is called turbo lag, which usually occurs below 2000 rpm in diesel vehicles.

As the engine rpm increases, more fuel burns, thus increasing the exhaust gas. Thus the operation of the turbocharger is also accelerated. Thus, when it reaches a certain rpm, the engine starts running without any lag.


Engines with turbochargers have a higher power-to-weight ratio, which means that they can generate more power at a smaller size.

If you want to know another advantage of turbocharged engines you have to drive at a high range area. Naturally aspirated engines will not perform well here as the atmospheric pressure is low. However, a turbocharged engine performs well in this situation as it pumps air.

Although turbo lag is a big challenge, the turbocharger is used in almost all diesel vehicles available in the market today. This is due to the efficiency of such vehicles. The automobile world is looking for ways to overcome turbo lag, when we get a way to solve this completely we will get performance vehicles without lag.

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