How Much Horsepower Does a Turbo Add: The Ultimate Guide to Engine Boost

Ever since the creation of the first internal combustion engine, engineers and customers sought more power. Even today, adding horsepower to an engine is more popular than meddling with any other part of your vehicle, although, arguably, upgrading the suspension, tires, and brakes will result in an ultimately better car to drive.

But I'm not here to preach about the best upgrade you can do to your car. Instead, I will focus on horsepower gains in this article. And the easiest way to add power to your engine is by slapping a turbocharger.

Okay, it's not as simple as just connecting a turbocharger – you will also need to prepare the engine for turbocharging. However, compared to any other upgrade, a turbocharger will bring the biggest gains.

But how much horsepower does a turbocharger add? Well, friends, this depends on many factors. Much like with engines, turbochargers aren't created equally and differ in size and boost.

Moreover, different engine designs also react differently to turbocharging. So, buckle up because we are going deep into turbocharging. It's going to be a wild but memorable ride!

The Turbocharger Evolution: From Boats and Planes to Cars

Turbochargers are part of most modern engines, both gas, and diesel, but it wasn't like that in the past. Let's have a look at the history of the most popular vehicle blower and see why it wasn't popular initially.

1. A Brief History of Turbochargers

The turbocharger was invented and patented by Alfred Büchi, a Swiss engineer, in 1905. However, it wasn't until 1925 that the turbocharger was first used commercially. However, it wasn't used in cars – two large passenger ships were the first to run turbochargers to add horsepower.

Later, though, turbochargers showed to be indispensable in aircraft engines. See, at higher altitudes, there is not enough air for the engine to produce high horsepower, and a turbocharger largely alleviated the issue by pushing more air into the engines. It was a match made in heaven until, of course, jet propulsion emerged on the scene.

Then, turbochargers were used in trucks with diesel engines before WWII, again, of necessity. The turbocharger added much-needed power to diesel engines and enabled trucks to carry more and heavier cargo, even on inclines.

But it wasn't until 1962 that turbochargers found their way into passenger cars (Chevrolet Corvair Monza and Oldsmobile Jetfire), almost 60 years after their invention. Although today most engines are turbocharged, in the past, they were seen as unreliable and unnecessary. Instead of turbochargers, carmakers simply installed larger engines and followed the mantra: there is no replacement for displacement.

2. The Science Behind Turbochargers

Turbochargers are quite an ingenious solution. They use the exhaust gases of the engine to spin a turbine, which then connects via a shaft to a compressor that forces air into the combustion chamber. This increased air intake results in a more powerful explosion, thereby boosting engine output and delivering more horsepower.

Every modern turbocharger's compressor uses a turbine "centrifugal" design that utilizes blades connected to a rotating shaft. The blades spin at very high speeds, up to 250,000 rpm, thus increasing the velocity and pressure of the air by utilizing centrifugal forces.

However, in supercharged engines, you might see other types of compressors, like a roots-type supercharger and a twin-screw supercharger. These turn at much slower rpm but can still produce a very big boost.

Factors Affecting Horsepower Gains from Turbochargers

Turbochargers can add a lot of horsepower to an engine, but other factors also affect how much power you will gain. Here is what you need to know.

1. Understanding the Engine's Compression Ratio

The engine compression ratio plays a crucial role in how much power the engine produces, be it naturally-aspirated, supercharged, or turbocharged.

However, its role is even more important in turbocharged applications. Namely, higher compression ratios can yield more power, but they also increase the risk of engine knock, limiting the amount of boost pressure that can be safely added.

So, with turbocharged engines, finding the perfect balance between the compression ratio and turbocharger boost is essential in achieving high horsepower gains without reliability issues.

In most tuned cars, you'll see the compression ratio is increased to allow for a larger turbocharger and a greater boost. However, this would create an engine that's not responsive and has lower rpm, i.e., a big turbo lag. Thus, for a daily driver, a combination of a higher compression ratio and a smaller turbocharger might be a more desirable solution.

2. Selecting the Right Turbocharger Size

The size of the turbocharger is directly correlated to the horsepower gains, i.e., a larger turbocharger will always give you a higher boost and more power.

However, the real-world experience is more complicated. Namely, a smaller turbo will spool up quickly, providing an immediate boost in power, but it may suffer from limited top-end performance. Thus, a smaller turbocharger would be better if you want a fun car on a twisty road, as the engine would always accelerate swiftly out of a corner.

On the other hand, a larger turbocharger might offer substantial peak horsepower gains but could suffer from increased turbo lag. Hence, a larger turbocharger would be a better choice for drivers that need more power at the expense of a good driving experience, like a dragster car, for example. Notably, cars with large turbochargers will be faster in a straight line but not necessarily on a twisty road.

3. Balancing Boost Pressure and Engine Capabilities

Balancing the boost pressure and compression ratio is important not just for optimizing the driving experience but also for reliability. Namely, increasing boost pressure will stress the engine components and could result in damage if not managed carefully.

Therefore, it is essential to balance boost pressure with the engine's ability to handle the added stress to ensure reliability and longevity. Or, if you really want to go overboard, you might want to invest in forged internal engine components, which are designed to endure the added mechanical and thermal stress.

Turbocharged vs. Naturally Aspirated Engines

The age-old debate among enthusiasts is whether turbocharged or naturally-aspirated engines are better. Both have their strengths and weaknesses and for most people, it comes down to personal preference.

1. Pros and Cons of Turbocharged Engines

Although many car enthusiasts prefer naturally-aspirated engines, there is no question that turbocharged engines produce more power. Moreover, turbocharged engines tend to be more fuel efficient when driven daily and are generally better for the environment.

However, they also have some drawbacks, such as increased complexity, the potential for turbo lag, and higher maintenance costs compared to naturally aspirated engines.

Moreover, turbocharged engines tend to consume more fuel when driven hard because some of the fuel is needed to cool the cylinder walls due to the higher temperatures and pressures.

2. Horsepower Comparisons Between Turbo and Non-turbo Engines

When comparing engines with similar displacement, turbocharged engines will typically be more powerful than naturally-aspirated engines. For example, a 2.0-liter naturally-aspirated car will have around 150 hp to 180 hp, while a turbocharged one will have up to 400 hp in some applications. Naturally, this results in better overall performance.

With that said, a fairer comparison would be between a larger naturally-aspirated engine and a smaller turbocharged one. In general, you will need 1.5 times the displacement to produce similar horsepower in a naturally-aspirated engine compared to a turbocharged engine.

Turbocharger vs. Supercharger

Turbochargers aren't the only option for potential engine tuning, nor the only technology that adds boost to an engine used by carmakers. Superchargers are another popular solution that many drivers prefer, though not as represented in modern times as turbochargers.

As I already mentioned, the turbocharger uses exhaust gases to run the compressor. On the other hand, superchargers connect directly to the crankshaft of the engine via belts, chains, or gears. Thus, it's the crankshaft that drives the compressor, which then sends the compressed air into the engine.

Superchargers are generally easier to install and less complex. Moreover, they tend to produce a similar driving experience to a naturally-aspirated engine, with no lag, because they don't need to spool up to produce a boost. Another advantage of superchargers is that they produce less heat.

However, superchargers are less efficient and consume more fuel. In addition, turbochargers can produce more power, which makes them the preferred choice among potential tuners.

Turbocharging Technology: Types and Applications

The original turbocharger design hasn't changed much through the years and still uses exhaust gases to run a compressor. However, carmakers devised intelligent ways to increase their productivity and efficiency by using two turbochargers or variable geometry turbochargers. Let's have a closer look at all turbocharger technologies used in cars.

1. Single Turbocharger Systems

A single turbocharger system uses one compressor to feed air into all cylinders. These systems are the simplest and most cost-effective and are still widely used in modern turbocharged cars. With good engine management, single turbocharger systems can produce high horsepower gains with minimal turbo lag. Still, the turbo lag will be there and noticeable during performance driving.

2. Twin-Turbo and Sequential Turbocharger Systems

Using two turbochargers gained traction in the 90s', when many famous cars, like, for example, the Toyota Supra MkIV, used the technology to minimize turbo lag.

The Japanese icon had a twin-turbo sequential system or two turbos of different sizes to ensure optimal response across the entire RPM range. The smaller turbocharger would give the engine better low-rpm response, while the larger would provide higher horsepower numbers at high rpm. Sequential twin-turbo setups redirected the airflow from one turbocharger to another at a certain rpm.

However, on some sports cars, you will find parallel turbocharger setups used mostly in V-shaped engine blocks. In these engines, each turbocharger supplies one cylinder bank with pressurized air, meaning both turbochargers spool at the same time. In other words, they employ turbochargers of similar size. The best example of such a configuration is the Ferrari F40.

3. Variable Geometry Turbochargers (VGT)

Variable Geometry Turbochargers adjust the compressor's geometry to change its speed. As a result, VGTs can produce more high-end power without sacrificing low-end torque, i.e., they minimize turbo lag.

Moreover, they result in increased efficiency, making them a popular choice for both performance and economy-focused applications. Most modern turbocharged cars have VGTs.

Customizing Your Ride: Upgrading to a Turbocharged Engine

Although many newbies think that upgrading a regular engine to a turbocharger is easy, it is one of the most complex upgrades.

1. Important Considerations for Turbocharger Installation

Adding a turbocharger to a naturally-aspirated engine necessitates many other changes simply because the motor wasn't designed with turbochargers in mind.

Before adding the turbocharger, you should consider several factors, including engine compatibility, fuel and ignition system upgrades, and cooling requirements.

You can learn many things from online forums, but I still strongly recommend consulting a professional or researching extensively to ensure a successful installation and optimal performance.

2. The Impact of Supporting Modifications

When upgrading to a turbocharger, you will also need to change other parts in your engine to ensure it runs properly. For that reason, most turbocharger upgrades come in kits, which include all the necessary parts for a trouble-free upgrade.

Still, aftermarket tuners don't support most engines and only focus on the famous ones. Thus, you will need to separately source a new exhaust system, add an intercooler, put in new fuel injectors, and upgrade the engine management system.

3. Ensuring Reliability and Longevity

After turbocharging your engine, it is essential that you give it extra care to ensure it runs without issues. This means adding high-quality oil designed for turbocharged engines, being cautious not to overheat the engine, and generally being gentler – driving at high boost all of the time will almost certainly result in engine failure.

With All That Said, How Much Horsepower Does a Turbo Add to an Engine?

Ah, yes, the question that made me write this article – how much power should you expect to really gain? Sadly, there is no straightforward answer to this, as you probably learned by now. There are many factors in play here, including the size of the turbocharger, boost pressure, engine size and configuration, compression ratio, and supporting modifications.

In general, adding a turbocharger to an engine will add anywhere from 40 hp to 300 hp, but in some cases, much more. In my eyes, a healthy boost of power would be around 50%. For instance, if your engine has 200 hp, you can push it to 300 hp without many reliability issues. If that doesn't sound like much, remember that by adding a turbocharger, you will also significantly increase the torque, which is equally significant for acceleration.

I wouldn't bother adding a turbocharger just to get a 30-40 hp boost, but I will also be careful pushing any engine to more than 50% of its original horsepower rating. It can be done, but it requires significant reinforcements to the engine block, stiffer internal engine components, a new crankshaft, a heavily-revised cooling system, etc.

The Future of Turbocharging and Horsepower

Turbochargers continue to play a big part in the automotive landscape, even with electrification. Here is what you might expect in the next decade regarding turbochargers.

1. Advances in Turbocharging Technology

As turbocharging technology continues to evolve, new advancements such as electric turbochargers and more efficient materials are expected to further improve performance and efficiency.

These turbochargers can greatly reduce fuel consumption but also eliminate turbo lag and improve the driving experience. Moreover, electric turbochargers can significantly reduce emissions, which is probably the most important aspect of the technology.

However, electric turbochargers can't run on a regular car battery – they require a 48-volt system. Thus, for now, they are reserved for some very expensive vehicles, though, like with every technology, electric turbochargers will eventually be available in cheaper vehicles.

2. Hybrid and Electric Vehicles

Turbocharging offers a viable path to increased power output without sacrificing efficiency, making it a key player in the development of environmentally friendly high-performance vehicles. Therefore, most hybrids going forward will also use turbochargers, aiming to improve efficiency while also producing more power.

Iconic Turbocharged Sports Cars

Perhaps the sports car that revolutionized the term "Turbo" was Porsche's 911. Even today, the 911 Turbo stands for exceptional performance and daily usability, with 0-60 mph times that rival electric vehicles. Another Porsche sports car that had a famously powerful turbocharged engine was the 959, which was once the fastest vehicle on the planet.

BMW, Audi, and Mercedes-Benz also use turbocharged engines in many of their performance vehicles, like the BMW M5, Audi RS6 Avant, and the AMG GT. Volkswagen also uses a turbocharged engine in the latest GTI and Golf R models.

The Japanese automotive industry is also famous for its legendary turbocharged engines, like the 2JZ-GTE (Toyota Supra) and RB26DETT (Nissan Skyline GT-R). Mazda even turbocharged a Wankel rotary engine in the RX-7, while Toyota recently introduced a three-cylinder turbocharged engine with 300 hp (GR Corolla).

Conclusion

Although a significant portion of car enthusiasts swear by naturally-aspirated engines, there is no question that turbochargers changed the automotive landscape for the better. I mean, who can be against more power?

And it's not just a question of how much horsepower turbochargers add – they also play a significant role in decreasing CO2 emissions. Not to mention, modern turbo engines are also more efficient, meaning less money at the pump and more smiles.

With that said, are you interested in turbocharging your existing car? If you are planning an upgrade, please do tell us in the comments what it is and the horsepower gains you are expecting!