The Basics of Turbochargers, Boost and How Forced Induction Changed the Game


With naturally aspirated engines slowly being phased out by more efficient and more powerful force induction counterparts, turbochargers are becoming more and more mainstream. Today we are going to take a closer look at this piece of machinery that has completely transformed the automotive world, as well as motorsports in general.

What is a Turbocharger?

Internal combustion engines work by burning a fuel mixture that is part gasoline (or diesel depending on the engine type) and part air. This has always been the case. Gas on its own doesn’t burn all that efficiently. Much like many other liquid flues, it needs an oxidizer which is air in this case.

Over time, people have noticed that forcing more air into the engine allows them to push more fuel in there as well, which ultimately produces more power. This is where turbochargers come into play.

Your average turbo consists of a compressor wheel and a turbine wheel, which are connected by a shaft. These two wheels each sit in their own, separate housings.

The way turbos work is quite ingenious. The exhaust gasses from the engine that usually go straight into the exhaust system, are routed to pass through the turbo side of the charger, forcing the wheel to spin as the thermal energy of the exhaust is converted into kinetic energy.

Since the turbine wheel and the compressor wheel are connected, the compressor side of the turbo starts drawing in air from the air intake system. The air is then forced into the intake manifold, thus creating forced induction.

There is one more important component that needs to be mentioned, and that is the intercooler. The sheer force of the compressor wheel results in a rise of air temperature as the air is moving from the turbo and into the intake manifold.

Since hot air is less dense than cold air, pumping into the engine would yield underwhelming results. Instead, what you want to do is pump in the cold air as it’s much denser and thus contains more oxygen to burn.

In order to cool the air down, every turbo is fitted with an intercooler unit. This component looks exactly like the radiator in your car, only smaller. As a matter of fact, you will often find it in front of or near the radiator in a turbocharged car.

Turbochargers VS Superchargers

Before we go any further, we need to briefly touch upon superchargers for two reasons. First, because they represent the other side of the forced induction coin and second because people often confuse the two systems.

Superchargers, much like turbos, are used to force air into the engine in order to boost its power. However, there is an important difference between the two. While turbos use exhaust gasses to spin up the turbine/compressor assembly, superchargers are actually powered by the engine itself. Namely, a supercharger is linked to the engine via a belt and pulley system.

The main difference between the two is that superchargers offer a more linear boost in power, while turbos only activate at a specific RPM range.

What is Turbo Boost and How It Affects Performance?  

Turbo boost or boost pressure are both terms used to describe the amount of pressure in the intake manifold as the turbo is forcing air into the system. Measured in either Bars or PSI depending on the car make and model, a turbo boost can tell you just what kind of power you have at your disposal at any given time.

One interesting thing to note about boost is that it changes with altitude. There is a common misconception that turbos create pressure out of nowhere. That’s not really the case. Instead, turbos create boost pressure by multiplying the air pressure in whatever environment the engine is operating in.

We can explain this with a simple example. We’ll use bars as it’s easier to work the numbers. At sea level, the pressure of the air surrounding you is 1 bar or 1 atmosphere. Let’s say that your boost gauge will show 2 bar of boost and every additional bar of pressure will be added on top of that.

However, if you were to take your car for a drive in the mountains at say, 2000 meters of altitude, your car is no longer creating 2 bars of pressure but 1.8 bars. Why is that? Because atmospheric pressure at 2000 meters is only 0.8 bars.

Therefore, the amount of boost and the overall performance of your car will depend on the altitude you’re on.

How to Increase the Power of Your Turbocharged Engine?  

There are several ways you can increase the power of your car if it has a turbocharger. Here are the main two methods widely used today:

  • Adding more boost to the stock system – Adding more boost to the stock turbo is the first step in reaching a higher power output of any turbocharged engine.
  • Swapping the turbo for a larger unit – Once you reach a specific stage of modding, you’ll find that your stock turbo is no longer cutting it. This is where adding a bigger turbo comes into play.

Let’s talk about each of these methods in detail.

Adding More Boost to the Stock Turbo

One of the easiest ways to gain more power from your turbo is to simply apply more boost. This is done by adjusting the wastegate on the turbine. Wastegate is a device that alleviates the excess exhaust pressure once the desired boost pressure is achieved. It is essentially a safety feature built into the turbo to prevent any issues with overpressure.

Manipulating the wastegate is done by adding a boost controller onto the wastegate. Since most wastegates measure the pressure in the system to adjust how far the wastegate opens up, adding a boost controller allows you to regulate that value.

You are essentially fooling the wastegate to think that the turbo is producing less boost than it’s actually is.

There are different types of boost controllers out there, including manual and electronic kinds. Figuring out which one will work best for you depends on the make and model of your car.

Upgrading the Turbo 

The issue with adding more boost to your stock turbo is that it’s very easy to push it to its limits. When this happens, your only option is to for a beefier turbo. At this point, you are probably wondering why don’t car manufacturers simply use bigger turbos from the start? There are several reasons for this:

  • Smaller turbos spool up faster – This is one of the big reasons why smaller turbos are so prevalent. A small turbine is much easier to spool up making them more efficient for day to day driving.
  • Low-end power on demand – Another important trait of smaller turbos is lots of boost in the lower RPM range. Since most drivers use their cars in such a way that depends on low-end power, car manufacturers often calibrate their turbos to offer plenty of boost in this RPM range

Installing a larger turbo does two things – it allows you to move more air into the engine, thus creating more boost and it allows you to tap into extra power in the higher RPM range. Since we are talking about performance upgrades, it’s fair to say that most drivers interested in this topic will want top-end power.

However, upgrading the turbo is no small feat. Oftentimes you’ll need to upgrade more than just the turbo itself. For example, an exhaust mod is just about guaranteed as you’ll most likely need optimized exhaust flow.

The complexity of this job will absolutely depend on the make and model of the car, but one thing is for sure – you’ll have to plan the whole thing with a lot of caution. Whenever you’re dealing with excess pressure and things that spin really fast, you kinda have to be careful.

Once the new turbo is in place, the next step is to tune it up. This is done by taking the car to a tuning shop, lifting it on a dyno and measuring its performance. Once the technicians have established a baseline output, they can start tuning the ECU map in order to take advantage of your beefier new turbocharger.

At the end of the day, if everything is done correctly and you’ve done your homework, you should end up with a car that goes faster, produces more power and has a power curve that yields the best performance.

Summary

Turbos are by far one of the best things to have happened to the automotive industry and car enthusiasts in particular. Playing with turbos is a great way to squeeze more power out of your car with stock components. However, you can go much further than that if you wish to. What matters the most is that you have the option to go either way. That’s more than naturally aspirated engine owners can say.

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