Learn what a car turbo is and when it is activated to boost engine performance. Discover the benefits of turbocharged engines for power and efficiency.
A few decades ago, a car with a turbocharger usually had a label that clearly indicated it. In just a few years, practically any new car you look at has one too. However, it is such a common element that it hardly gets the publicity it deserves.
The turbocharger, which is its full term, is a boost system . Specifically, it is the most used of all. Without giving away too many details, its function is none other than to be able to get more power from an engine . In the past, the turbo was mainly used in sports cars. Nowadays, the turbo has turned the tables. It is used to boost, yes. But manufacturers are mainly using it to reduce consumption and minimize emissions.
Do you want to know what they are selling you when you go to a dealership to buy a new car? Do you need to know what advantages a turbocharged car has and how it is driven ? Just stay and we will tell you as always: in a simple and very entertaining way.
Understanding the atmospheric engine
To understand what a turbo does and how it works, we need to look back a little further. We need to understand how the intake of a car without a turbocharger works . This will be brief.
A combustion engine always runs on fuel (petrol, diesel, alcohol, LPG, etc.) and air. Air contains the oxygen needed to produce combustion.
In a normal engine, air enters through the intake exactly as we humans breathe, aided by the pressure of the atmosphere itself . Normally, we say that these engines do not have any kind of boost, and we refer to them as “naturally aspirated engines”.
Naturally aspirated engines have many advantages, but their main drawback is that they have certain barriers to generating more power. After all, atmospheric air is as dense as it is, and the engine has no tools to increase that flow .
What is a turbo?
The turbocharger is nothing more than a device capable of putting pressurized air into the engine cylinders. By introducing compressed air, there will be more oxygen in the same volume . Since this acts as an oxidizer, more fuel can be burned.
As we have been saying, the idea behind equipping a turbo in an engine is to obtain more power . However, at the same time that this component has been evolving, its way of being applied has also changed:
- In its early days in the automotive industry, the turbo was only fitted to high-performance petrol engines .
- Since the late 1990s, virtually all diesel engines have been fitted with turbochargers. The design of diesel engines, which were tough and heavy, required large displacements, but produced very little power. The turbocharger was the key to the success of these engines, providing them with more power while maintaining low fuel consumption.
- Today, turbocharging is used in almost all new gasoline engines . Thanks to it, manufacturers have been able to reduce displacement – or even remove cylinders. This means that a small engine can achieve decent power with low fuel consumption and emissions that pass the homologation requirements.
The other great advantage of the turbocharger is that it allows the engine’s torque and power curves to be optimised . Since there is electronic management of the intake, the car’s control unit can optimise fuel intake much better. The result is quite interesting, as wide ranges of revolutions are achieved in which these engines will respond with a more sustained delivery of torque (in the case of diesel engines) or power and torque (in the particular case of petrol engines).
What parts does the turbo have?
As its name suggests, a turbocharger is the union of a turbine and a compressor . And this is quite interesting to note, since there are notable differences between a vehicle with a turbocharger and one that simply uses a compressor. Each main element of this system does the following work in the whole:
Turbine
The turbine is the component of the turbocharger that starts the system. It is a shaft that is very cleverly driven by the exhaust gases from the engine itself.
The turbine is located inside the exhaust snail . With the gases, it rotates at tens or even hundreds of thousands of revolutions per minute. The movement of the turbine makes it possible to drive the compressor, as we will see later.
Compressor
The compressor is not that mysterious. If you have ever inflated a mattress, you can already get an idea of how it works. This element, when connected to the turbine, compresses the air that comes from outside to later introduce it into the motor.
The more compression capacity this element has, the more air – and therefore oxygen – can enter the engine. That, as we said before, translates into greater capacity to burn more fuel.
Snails
These are the spiral covers that surround both the turbine and the compressor. This element has two parts:
- Exhaust snail : receives the exhaust gases from the engine. The gases spin the turbine, which in turn drives the compressor on the other side.
- Intake snail or cold snail : this is the one that draws fresh air from outside (and, therefore, loaded with oxygen) and directs it to the compressor.
Intercooler
We have already talked to you about what a car intercooler is and how it works. Here we will simply give you a few simple brushstrokes so that you understand the context.
Air heats up when it is compressed, and that is not good for the engine. The job of the intercooler is to cool it before it is introduced into the cylinders, achieving better combustion efficiency .
What types of turbo exist?
There is no single type of turbo design . Depending on the car, the performance to be achieved and the task to be performed, one type or another can be used.
Boosting an engine with a turbo is not that simple. The turbo, as we said, is powered by exhaust gases. And an engine does not generate many exhaust gases when it turns at low revs . Apparently, when we are going to need the turbo the most, it can help us the least. That is why there are different types of turbochargers that may be more or less suitable for each type of car. The most used and interesting ones are the following:
Single turbo
The simplest modern cars use basic turbochargers . They are relatively inexpensive and not so complex. In the previous lines we have already explained how they work, although we have not gone into detail about their disadvantages.
The single turbo has a fairly narrow effective rev range. Manufacturers have to decide on the size and design of the component to optimize its operation at low or high revs . In addition, they generally take a while to kick in, which is known as turbo lag .
The other designs that we are going to see below are designed precisely to fix these problems .
Twin turbo
This is an application used in high performance cars . Although they are much more complex, they have two key applications:
- Parallel : Two identical turbos are used, and are installed in “V” engines. Each turbo feeds a bank of cylinders.
- Sequential : This is an ingenious solution when you have a large engine and want to eliminate turbo lag. First, a small turbo is used which kicks in very early, at low revs. Then, the large one takes care of maximising power when driving at a higher rev range. All advantages.
Variable geometry turbo
Instead of using two turbos, which is more expensive and complex to implement, many manufacturers opt for variable geometry turbos (known as VGTs). In these, the vanes inside the system change their convergence depending on the engine revolutions.
These mechanisms are not cheap, but they are very effective. The delay is substantially reduced and good response is achieved in practically the entire range of revolutions . These devices are widely used in Volkswagen Group diesel engines and work very well, although they wear out more than other alternatives.
Turbo twin scroll
This other peculiar design is used quite a lot by BMW with a technology that it calls “TwinPower Turbo”. It consists of dividing the exhaust manifold into two ducts . The idea is that the back pressure of the exhaust system does not hinder the mechanism itself.
Thanks to this design, the engine also achieves good response at low revs .
Variable twin scroll turbo
It is an evolution of the twin scroll developed a few years ago by BorgWarner , which is one of the most important turbocharger manufacturers in the world.
This system combines the strengths of variable geometry turbos with twin scroll turbos. The design is based on a twin scroll with a valve that allows the exhaust gases to be redirected . This allows the flow of gases to be optimized, either by taking it to a single scroll or by dividing it. For gasoline vehicles, this system is much more effective than the variable geometry model, since there is a wider range of revolutions to be covered by the turbocharger.
Electric turbo
Just because exhaust gases power the turbo doesn’t mean that turbocharged cars pollute more. However, if emissions regulations are tightened further, there is still an additional alternative .
The electric turbo is simply a system that achieves the same goal, but without using exhaust gases . Thanks to an electric motor, the turbine can be rotated to activate the compressor. The delay would be eliminated, although it would depend on an electrical system that also consumes energy . In any case, it is a system that may soon be adopted in hybrid cars.
How does the turbo work? When does it come into operation?
The way the turbocharger itself works is quite clever. When the engine is running at a slow speed, the exhaust gases will not have enough force to quickly move the turbine and introduce a lot of air through the compressor. Therefore, we could say that at those speeds, they work almost like a naturally aspirated engine.
When we need more power, we press the accelerator harder. This allows more fuel mixture to enter the cylinders. Obviously, this results in more exhaust gases, which spin the turbine . As a result, more compressed air enters the engine, like a dog chasing its tail.
The gearboxes themselves in turbocharged cars are also optimized for efficiency. The idea is that when changing gear, the revs drop to a level where sufficient exhaust gases are still produced for the system to continue feeding back . It would be pointless to shift up a gear and have the car completely come to a halt under full acceleration.
How much power does a turbo give?
The power that an engine can gain by implementing a turbocharger depends on a multitude of factors . The normal thing is to make the comparison on the base engine, that is, to measure the difference with respect to the same engine if it were naturally aspirated.
Manufacturers usually talk about power gains above 30% , although this is still a guideline. However, everything depends on several factors:
- Small turbo vs. big turbo : the small one responds well at low revs. The big one, the opposite. In small cars for more urban use, the first is ideal. For vehicles intended for the road, the second is optimal, but has much more lag .
- Mechanical design : Every engine has its limitations. If we put too much pressure on, that pressure will eventually escape somewhere. You can put as much pressure on as the mechanics can handle. Of course, no manufacturer is going to sell you a car that pushes the engine to the limit. Reliability is always a priority.
- Electronic management : closely linked to the latter, which we have just mentioned. Electronic engine management is designed to ensure the engine’s useful life. By adjusting the values - that is, reprogramming the control unit – you can almost always get extra power. Is this advisable? Ideally, no.
- Turbocharger specifications : some turbos are more capable than others. There are very powerful turbos that work with very high pressures. However, a reinforced engine is required to withstand such pressure.
- Exhaust system : being a key part of the system, it can also facilitate or hinder the arrival of gases to the turbocharger.
- Other elements , such as the intercooler, can also have some importance in the overall package and in the total power gain.
Since we have already mentioned “repro” in this section, we invite you to read this guide that we have already published on what happens if you reprogram your car and what the procedure is for. It is an article that is closely related to this topic of the turbo.
Now that you have read all these lines, you surely understand why it is often said that naturally aspirated engines are less problematic. Regarding the latter, in this article that we leave you to finish, we talk in detail about the most reliable gasoline engines.