Are bus engines turbocharged?

In this short guide, we will answer the following question: Are bus engines turbocharged? We will explain how a bus engine works, what does a turbocharged engine mean, and discuss many more questions related to the subject. 

Are bus engines turbocharged?

Yes, most of the bus engines made in the past few decades are turbocharged.  On buses, the engine is generally installed at the rear, lying down on the left side to free up space in front of the rear door, or upright, which allows better access for maintenance. There are also mid-engined buses and there are older buses that are not turbocharged.

Turbocharged engines currently offered for buses are from:

  • Iveco
  • Tector 7 (midibus and bus)
  • Cursor 9 (bus)
  • MAN
  • Engines D 0836 LOH
  • Mercedes
  • OM 906 hLA (170 kW or 205 kW)
  • OM 457 hLA (185 kW or 220 kW)
  • Volvo
  • D7C.

The engines have followed the evolution of standards. Now all are Euro 6 compliant. And the technical developments have led manufacturers to release new engines. The latest engines have higher power for smaller displacements.

What is the bus engine turbocharger used for?

The turbocharger increases the performance of the internal combustion engine. The engine derives its power from combustion between a mixture of air and fuel. The more the engine is fed by this mixture, the more power it gains. 

To increase the volume capacity of the engine, the volume of the cylinders is often increased or an additional cylinder is added. The same result is achieved by injecting more air into the cylinders. This is the role of the turbocharger.

How does the bus engine turbocharger work?

A vehicle without a turbocharger injects only fresh air (from the outside) into the combustion process. The turbocharger will also use the exhaust gases released from the engine: this improves engine performance while reducing fuel consumption and particulate emissions.

The turbocharger is equipped with a turbine and an air compressor driven by exhaust gases. The exhaust gases released from the engine through the exhaust manifold are directed to the combustion chamber in which the rotor is located. Through a common shaft, it drives the compressor rotor, located on the other side of the device (often called the “cold section”), which compresses the air supplied to the motor.

Since compressed air contains more oxygen in a unit of volume, it becomes possible to create better conditions for the combustion process. A greater amount of air combined with an additional amount of fuel can be used to increase engine power or, as in the case of diesel engines, allows for better combustion, by considerably reducing the number of pollutants emitted and increasing the capacity of the engine. engine efficiency.

Bi-turbo: what is it?

Many turbocharged engines have two turbochargers instead of one. These two turbos are slightly smaller and share the exhaust flow from the cylinders. Thus, if the system is equipped with 6 cylinders, each turbo will use 3 of these cylinders.

The main advantage of this turbocharged torque is the reduction in weight compared to a single large turbo. To have enough power, a single turbo of imposing size would need more energy. The vehicle would therefore need higher engine performance to accelerate. This is not the case if your car is fitted with bi-turbos that provide enough compressed air, even at low speeds. These also provide enough energy when the speed is higher.

Turbo lag: what is it?

Turbo lag refers to an abnormally long response time of the turbocharger after a certain speed is reached. Nowadays, this problem is no longer common. This is why this term refers instead to turbochargers from the 1990s.

How long does a turbo last?

Typically, the turbocharger lasts as long as the engine and does not need to be replaced. However, the life of the turbocharger depends on different factors, so sometimes replacement or repair may be required.

How to prevent damage to a bus engine turbocharger?

Most problems related to the turbocharger can be avoided with regular maintenance of your car. To prevent turbo failures, be sure to regularly change the engine to replace the oil and filter. 

Also, be sure to check the engine oil level and clean the air filter. By doing this, you are ensuring that your turbocharger stays in good condition for as long as possible and you avoid early repairs or replacement.

One of the most common problems is turbocharger fouling from debris or dirt in the oil.

A lack of oil in the engine can damage the turbine engine irreversibly and lead to an expensive replacement. Conversely, too much engine oil can raise the temperature and damage the turbine engine. Most problems with excessively high temperatures are triggered by faults in the ignition or fuel injection system.

Adapt your driving style to preserve the bus engine turbocharger

The turbocharger is subjected to very high temperatures due to the energy generated by the exhaust gases. A standard diesel engine can reach 1000 degrees. If the car is parked immediately after a long journey, especially on a motorway, heat can build up in the engine. Due to the lack of ventilation, the temperature cannot be properly regulated, which significantly reduces the life of your turbocharger.

Abrupt temperature changes should be avoided. If you are driving for a while on the motorway, we recommend that you slow down towards the end of your journey and do not park immediately in order to let the turbo cool down.

At the same time, be careful to avoid big temperature differences at the start of your journey: let the engine warm up a bit before driving at full speed.


The engine determines the performance of a thermal engine bus.  It is therefore the choice of the gearbox and the torque of the bridge which will determine the characteristics, and therefore the field of use, of a bus.

Depending on the parameters, it is possible to design a purely urban bus or a bus suitable for interurban routes, on the national road or on the motorway (in large urban areas). Many networks opt for versatile buses by choosing a compromise.

Now that you know how a bus engine works and what a turbocharger is, please feel free to share your thoughts, tips or questions related to the content. 

FAQ on Are bus engines turbocharged?

What is the role of the turbocharger?

The role of the turbocharger is to increase the level of oxygen (O2) in each cylinder by compressing the intake air.

How does a turbo intercooler work?

The operation of the turbo intercooler is very simple! At the outlet of the turbo compressor the air undergoes a sharp rise in temperature, the compressed air flow is therefore hot. It is therefore passed through an intercooler so that this airflow decreases and then goes to the engine in the combustion chamber.

What is the role of the turbocharger in the heat engine?

The role of the turbocharger is to increase the performance of the internal combustion engine. Indeed, the engine derives its power from combustion between a mixture of air and fuel.

How does a turbo petrol engine work?

The turbo petrol engine uses the speed of expulsion of the gases to make a propeller turn at a frequency greater than 200,000 rpm at this speed, the turbine drives a coaxial compressor wheel: a large quantity of air is then sucked in.


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