Turbocharger Explained

We get into the nitty-gritty of a turbocharger so you don't have to.

What is it?
A turbocharger, in a nutshell, is a component that helps the performance of a car by ramming fresh air into the engine with the help of exhaust gases that also come from the engine. Invented by Alfred Büchi in 1905, turbos have come a long way since. Today, they have become a standard part of the engine and not seen as a performance add-on. The working is fairly simple and you have some pros and cons along with many types of turbos in the market. And to be fair, there is a plethora of information and videos on the web to make you a Ph.D. in turbocharging. But, we have tried to simplify it, so the next time you hear someone saying gibberish like “stutututu” or making a “whooshing” sound, you know what they’re talking about.

How does it work?
A turbocharger is made up of mainly two components. A turbine and a compressor. Simply put, there is an outlet for the exhaust gases, which spins the turbine and acts as a suction pump for fresh air that is brought in from the environment. Confused? Okay, how about this.
The turbo is attached to the engine with one part of it bolted onto the exhaust manifold (where the used up air escapes through) and the other bolted onto the inlet manifold (where fresh air gets in from).
When the engine is running, exhaust gases are channeled through the exhaust manifold and into the turbocharger. These gases spin the turbine wheel attached to the compressor, which sucks in the fresh air.
That air is then passed through the air intake and fed into the engine.
However, the turbine that sucks in all that air is also compressing it and if you paid attention in school, compression of the air raises its temperature. And you can’t just ram in hot air into the engine as it isn’t as efficient.
To cool the air, you have a component called the intercooler.

It basically cools the air by making it pass over a mesh of fins before it reaches the engine.
There are two more parts that have been hugely impactful in the popularity of a turbo.
The blow-off valve and the wastegate. The blow-off valve is attached to the inlet manifold and is responsible for that “whoosh” sound as the excess air sucked in is being let off through here. The wastegate, on the other hand, is the component attached to the exhaust manifold and helps with releasing excess exhaust gases out creating the famous “stututu” sound also known as turbo flutter. ‘Turbo whistle’ is again something that hits the spot for car enthusiasts and is the result of the turbo spooling up rapidly and making an almost jet-engine-like sound.

What are the benefits?
In essence, it is an air pump and as we saw above, a turbo’s main job is to feed in more air into the engine so the fuel can burn better and you get more power. However, a turbocharger also helps with efficiency. Now, this might be more relevant to smaller capacity engines, but when driven carefully, and sedately, a turbocharged car will be more efficient than a naturally aspirated one. And if you ask, who in their right mind buys a turbo to drive sedately? We don’t know the answer either, but you have to admit, it is a good advantage.
The hot exhaust gases, that would have otherwise just escaped through the exhaust, are now being used to generate more power. Tell me that’s not a good thing.
A turbo is especially useful in small cars though, which is why you now have a myriad of 1.0-litre engines with turbocharging. It is the best of both worlds.

What aren’t the benefits?
Like with all good things, you have some downsides to a turbocharger as well. Bummer right?
To begin with, the biggest challenge with a turbocharger, especially a single-turbo setup, is turbo lag. Turbo lag is the extra time you have to wait while the turbo spools up and helps make more power. This is often the case with large turbos as they require more time to spool up. They do make more power, but that is towards the top-end of the rev-range.
Then there is the narrow powerband. If you don’t have lag and the turbo size is small enough for it to spool quickly, it can only spool up so much and that means you don’t get the boost for long enough.
Like mentioned above, turbos end up heating up quite a bit and to cool off, they take help from the engine oil and end up consuming a significant amount.

What are the types?

There are many types of turbos with each of them having its pros and cons. To list them out, you have:

Single Turbo: One of the most common setups and one of the simplest ones as well. They are known to be cost-effective, easy to install, and not take up too much room in the engine bay.
Twin Turbo: Seen on high-performance cars, a twin-turbo setup naturally makes a lot more power and is hugely effective especially on V-shaped engines. With a V6 or V8, you can attach two turbos, one on each bank of the engine, and eliminate any lag or delay. You can also have them in a sequential setup and tune them for low revs and high revs individually.
Twin-scroll Turbo: Most famously used on BMW engines, a twin-scroll turbo is basically a single turbo with two scrolls. That means each of the scrolls helps in inlet and exhaust of the air, aiding faster boost and better performance.
Variable Twin Scroll Turbo: This is a rare and complex turbo, but it is one of the most advanced ones out there. It relies on the principles of a VGT, but has better performance and is cheaper to build as well.
Variable Geometry Turbo: This one you have probably heard or seen on Hyundai cars and especially on the diesel variants. A variable geometry turbo is again, a single-turbo setup with vanes inside the turbo that help control the airflow on the spinning turbine. This results in more efficient working and results in better power delivery.
Electric Turbo: This is quite high-tech as we have seen its applications in Formula 1. The electric turbo solves pretty much every drawback of a regular turbocharger like turbo lag and excess heat. Gone is the delay in power or loss inefficiency. With an electric motor connected to the turbine, the turbo can spool up much faster and hence be a lot more effective. Obviously, they aren’t cheap, and it will be a while before you see them on city hatchbacks. But, it’s good to know the general direction in which turbos are headed.

Anything Crazy?
Over the years, manufacturers have had their fun and games with turbocharging, and here is the list of some of the wild applications.
1) Bugatti – The quad-turbo W16 engine is almost a wonder of the world. The four-variable geometry turbos on here feature a parallel setup (two on each side) dishing out 18.1PSI of boost at maximum pressure.

2) Audi – The SQ7 isn’t a car many would remember, but it was one of those crazy projects that makes you laugh every time you read about it. The 4.0-litre V8 was featured with a triple-turbo charger setup with two of the standard turbos in sequential layout and a third was the electric compressor that acted sort of like an electric turbocharger.

3) BMW – Who can forget the quad-turbo 7 Series. Dubbed the 750d, the ‘B57’ 3.0-litre, the in-line six-cylinder engine made a modest 394bhp despite having four turbos attached to it. Two of them helped low pressure and the other two in high pressure.