What's the Difference Between Turbocharging and Supercharging?

When it comes to enhancing engine performance, turbocharging and supercharging are the two primary ways. Both are forced induction methods that share the common purpose of boosting horsepower in normally aspirated engines. Although the two technologies are sometimes mistaken for one another or used interchangeably, distinct differences set them apart.

What is Forced Induction?

Mazda Skyactiv-G Turbocharged Engine

Photo: Christian Wardlaw

Essentially, turbochargers and superchargers are air compressors used to increase oxygen flow into an engine through forced induction, but each accomplishes this goal in its own way. 

Forced induction uses the principle that more air in the combustion process creates a greater output of power. By compressing air and increasing its density, forced induction allows more oxygen into the engine cylinder, calling for a correspondingly greater amount of fuel. More fuel means larger explosions in the combustion chamber which leads to more power generation. 

At higher altitudes, where the air is less dense, forced induction helps regain lost power by pressurizing air and squeezing more oxygen into the cylinders. Without forced induction, an engine is limited by the air density of the atmosphere around it, whether at sea level or 10,000 feet.

Turbo vs. Super: The Key Difference

Although both methods use forced induction, the fundamental difference between turbocharging and supercharging is how the air compression components for each system receive power. 

A turbocharger takes an indirect approach as it does not mechanically connect to the engine. Instead, it uses the stream of exhaust gas from the engine to spin a turbine that powers the compressor. 

A supercharger physically connects to the engine. It operates by using the engine's crankshaft as a direct energy source for the compressor. 

What is Turbocharging?

2021 Mazda CX-30 Turbo Skyactiv Engine

Photo: Christian Wardlaw

As exhaust gases pass through and spin a turbine, the turbine creates a vacuum that compresses air before forcing it into an engine's intake manifold. As the engine spins faster, so does the turbine, thereby sending even more air into the motor and boosting power by 25% to 40%. 

However, this system is not instantaneous. Since an exhaust-driven turbine takes time to spool up and the turbine must spin at a specific rate of speed for optimal boost, the system will often experience a lag. This delay, known as a "turbo lag," is a momentary lapse of power that occurs as the turbocharger tries to get up to speed.

Turbochargers are not as powerful as superchargers, but since they run off recovered energy in the form of exhaust gases, they improve the engine's overall efficiency. A turbocharger also utilizes a wastegate that reduces the emission of exhaust gases into the environment.

What is Supercharging?

2021 Jaguar F-Type Supercharged V8 Engine

Photo: Christian Wardlaw

A supercharger is connected to the engine by a belt or chain. As the engine's crankshaft spins, the supercharger spins along with it. Like with the turbocharger, the spinning creates a vacuum that compresses air and then forces it directly into the engine. 

The direct-drive relationship between the supercharger and the engine creates a linear powerband that results in an instantaneous boost of 30% to 50%. The supercharger provides this optimum boost throughout the rev band without any lag. 

This direct connection to the engine makes superchargers more powerful than turbochargers, but this also makes superchargers considerably less efficient. In the end, they are designed to produce engine power by drawing engine power. In some ways, they are like powering an air pump with another air pump.

Also, unlike a turbocharger, a supercharger does not utilize a wastegate. This means it emits more smog than its turbocharged counterpart.

The Pros and Cons of Each

While turbocharging and supercharging bring a significant increase in horsepower to normally aspirated engines, they each have pros and cons.

Turbocharging Pros:

  • Ideal for smaller displacement engine applications; often paired with four-cylinder engines
  • Lighter weight and lower impact on fuel economy
  • Overall more efficient powertrain operation due to energy loss recovery (exhaust gases)
  • Utilizes wastegate that reduces carbon emissions

Turbocharging Cons:

  • Presence of turbo lag 
  • Designed to provide boost within a specific engine operating range rather than across the entire rev band
  • Higher engine oil requirement due to extremely hot operating temperatures
  • Complex installation 

Supercharging Pros:

  • Produces significantly more horsepower than turbocharging
  • A quick solution to boosting power in larger displacement engines with more cylinders
  • No power lag as is seen with turbocharging; power delivery is instantaneous
  • Delivers power boost at low engine revs in comparison with turbochargers
  • Experiences longer life and less heat wear than turbocharging

Supercharging Cons:

  • Absence of wastegate results in more carbon emissions
  • Lower fuel economy due to direct power draw from the engine
  • Louder and more abrasive sounding than turbocharging

Summary

Although the saying goes, "there is no replacement for displacement," turbochargers and superchargers are both highly effective ways to get more power and performance from any engine. But each system comes with a unique set of trade-offs. For those looking to balance performance with fuel economy and efficiency, turbocharging is the better choice. For those more interested in a straightforward solution to raw horsepower, supercharging is more likely the way to go.