How Much Horsepower Does A Turbo Add?

Adding a turbo will add a lot of HP (horsepower) to your car. Here's the ultimate guide so you can know exactly how much horsepower a turbo adds.

A turbo is one of the biggest ways to dramatically increase how much horsepower your engine puts out.

While it’s true that you could see significant gains, don’t be fooled. Real life isn’t like Instagram or the movies.

You’ll need real expertise and a functioning shop (or to pay someone else a lot of money).

You can’t walk up to your car and throw a turbo at it. There are so many other things to do.

Think you’re up for it? Read on.

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How Does A Turbocharger Work?

In simple terms, a turbocharger – known colloquially as a “turbo” – is a turbine.

This turbine spins as exhaust gases pass past it. It’s connected to another turbine by a shaft. By quickly revolving, this side of the turbo sucks in air from the atmosphere.

It isn’t just standard air, though. Remember, a vacuum’s been created. It’s sucking much more air in than it would otherwise, so the air’s under pressure.

The pressurized air (“forced air”) passes across an intercooler to lower its temperature. The colder it is, the greater the oxygen density, so the better it burns.

From here, it’s recirculated back to the intake. The air is “forced” into the cylinder, creating a very efficient burn.

Thus, the cycle continues.

It’s a form of forced air induction. The other well-known type is the supercharger. It operates on a similar principle but is directly driven by the engine, not exhaust gases.

Why Does A Turbo Increase Horsepower?

Turbo charger on car engine

A turbo forces much more oxygen into the engine. This leads to a much more powerful explosion when the spark plug ignites the air/fuel mixture.

As a result, it drives the piston down with much more force. This translates into an increase in horsepower.

The best analogy to explain this is to consider bellows and a traditional fire.

When you’re struggling to get a fire going, you use bellows to force much more oxygen into the fuel (wood/coal). Even blowing on a flame is the same principle.

To create fire, the fuel reacts with oxygen and heat. The more oxygen there is, the more catalyst there is for the reaction, and the more intense the flames become.

At the same time, you need to add more fuel to the fire, or else the flame is wasted.

This is an analogy for a turbocharger. It adds much more oxygen to the mix. At the same time, you need to remap your ECU to inject more fuel into the combustion chamber.

What Else Do You Need To Do A Car When Adding A Turbo?

Car ECU

In reality, you shouldn’t ever add a turbo and think, ‘That’s it – I’ve finished.’ There’s so much more work you need to get done. If you don’t do the following, it’ll create severe problems, up to and including engine failure.

When you attach a turbocharger, you absolutely must:

  • Remap (or chip) your ECU
  • Adjust the timing (if done manually)
  • Adjust spark plug gaps
  • Install better fuel injectors
  • Ensure the turbo is lubricated and adjust the oil pressure accordingly
  • Get it tested to find the new limits of your engine

If you don’t do these, you’ll run lean (too mix air in relation to fuel) and potentially misfire (and therefore lose power). The turbo will also immediately overheat and break without an oil supply.

It’s also highly recommended that you:

  • Upgrade your brakes to performance brakes
  • Rebuild engine, replacing piston rings and other important components
  • Upgrade your transmission – the original probably can’t handle the excessive force now passing through it
  • Fit high-quality tires
  • Install other performance parts, like an exhaust, valves, camshaft, etc.

You’ll be significantly increasing the amount of power the engine’s trying to produce. The drivetrain is then attempting to get this power down to the wheels and the road. Can all the components handle it?

It’s best to not leave it to chance!

Can You Install A Turbo On Any Car?

Engine Replacement Cost

It would be foolhardy to try without modifying certain cars to an extreme extent.

For example, if you drive a car with a 1.0-liter I4, don’t bother. The engine is too small to handle a sudden increase in force. You’ll only gain horsepower in the single digits, and the trade-off? Probably serious engine problems.

As mentioned, you also can’t install a turbocharger without significant other modifications. You must be able to adjust the timing and fuel mixture settings. Without doing this, you’ll run lean and damage your engine.

In essence, the larger your engine is, the more suited it might be to a turbocharger. You can technically add a turbo to any car, but bigger engines are your best option. They’ll see the most gains.

Larger engines create more exhaust gases. Therefore, there’s more force to drive the turbo turbine, and more boost potential as a result.

What Sort Of Turbo Should I Install?

Turbo Charger In Car

Large turbochargers take a while to spool up. That means you’ll initially accelerate slowly before feeling the boost kicking in.

Small turbochargers spin up and force air in much quicker, but there’s a limit to how much pressure they can hold.

To counter this, a twin-turbo system can be installed. This pairs two turbos, giving you a high and low rpm boost. There are several different ways the two can be set up.

This article will continue to focus primarily on single turbos.

How Much Horsepower Does A Turbocharger Add?

Pistons and Cog Wheels Performance Horsepower

Unfortunately, the clear answer you might be looking for simply doesn’t exist. Here’s why.

You can expect horsepower gains of anywhere between 5% and 100%. That is, every car is different.

It isn’t reasonable to think that adding a turbo will increase your car’s power by a set amount.

That being said, it’s true that most cars, when fitted with a turbo, would see horsepower gains of 10% to 50%. That’s still a wide range.

The bigger your engine, the more potential there is for more horsepower.

The reason for all this variance comes down to:

  • Engine size and how much force it can withstand
  • Additional modifications (you have to do some, at least)

How Much Horsepower Does A Twin Turbo Add?

Twin Turbo System

A twin-turbo system won’t add too much horsepower to an engine, although you might see a small increase compared to just one. That said, you’ll see major performance increases.

There are lots of factors to consider here.

First, think about what “horsepower” actually means. It’s referring to the peak power – the most you ever get out of your engine.

Twin turbos might lead to a better power curve, but they won’t influence the peak power much. That is, in relation to a single turbo.

Second, what’s the frame of reference? All turbos are slightly different from each other and produce different results.

One well-designed turbocharger might increase hp output more than two poorly-designed ones in a twin system.

Some twin-turbo systems pair a large turbo (for high rpm) with a small one (for low rpm). If you removed the small one, you’d still see about the same power output, even though acceleration would be far poorer. This is because the peak horsepower is still around the same.

Finally, you still have to consider all the variables mentioned before. The overall result depends entirely on the other accompanying modifications you make.

How Much Horsepower Does A Turbo Add To Certain Engines?

In this section, you’ll see approximations of how much horsepower turbos add.

Again, it’s crucial to stress that the results vary so much. It’s largely dependent on your engine size, but there are still many more factors.

How Much HP Would A Turbo Add To An I4?

Inline 4 Engine

In general, don’t expect more than a 10% horsepower gain for Inline-4 engines.

They’re the fundamental workhorse of the engine family, known for plodding along and getting the job done. Nothing special, nothing terrible.

Adding a turbocharger to a naturally-aspirated I4 is a bit like putting your Grandma behind the wheel of a Formula 1 car. It’s just not made for it.

(Across most of the world, turbos are fitted to I4s by manufacturers to increase fuel economy. In the US, this trend hasn’t caught on.)

With all that said, if you’re up for the challenge, go for it!

In small hatchbacks, don’t waste your time on anything naturally-aspirated and less than a 1.4. If you’re looking at heavier cars with an I4, you’ll need at least a 1.8.

How Much HP Would A Turbo Add To A V6?

V6 engine

It’s fair to guess that you’d see 15% to 25% gains if you fitted a turbo to a V6.

V6s already have the potential for more power output than I4s. Adding turbos will see more obvious benefits.

For example, if you already have 200 hp, you should expect a turbo to raise it to about 250 hp.

How Much HP Would A Turbo Add To A V8?

V8 Engine

If you expect gains of 20% to 40% on V8 engines, you’re unlikely to be disappointed.

You could increase those numbers with some efficient tuning. It all depends on the same factors, as always.

V8s – in fact, all V-engines – are perfect for twin-turbo systems. One turbocharger can be fitted to each block of the “V”. You can expect crazy acceleration.

Concluding Thoughts: Is A Turbo Worth It?

Mercedes AMG Turbocharger

Should you get a turbocharger fitted?

It’s certainly a fun option. In the end, it’s up to you, but remember the following:

  • It’s best to start with a large and powerful engine
  • Remap the ECU and adjust the timing and engine components before turning the car on
  • Modify the rest of the car to prevent damage, improve performance and handling, and increase safety
  • Be prepared to spend vast amounts of money for a professional to do it for you. You can always try adding a turbo yourself, but there are so many things to consider. Doing something wrong could – no, will – damage your engine.

Paying for a new turbo and all the accompanying modifications will cost you thousands of dollars. Perhaps tens of thousands.

A better use of your money is often to trade your current model for a faster stock model. But if car modification is your passion or way of expressing yourself, why not? Go for it!

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Benjamin Kitchen

Ben is an automotive author from England. With experience in a fast-fit garage, he's an IMI-qualified light vehicle technician. He aims to help drivers worldwide with common automotive problems. You’ll often find him working with his 1.2 Vauxhall Corsa – it may have a tiny engine, but in eight years it's never once let him down!

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