If you’re looking for ways to boost your car engine‘s power, you’ve probably come across the long-running debate between fans of superchargers and turbochargers. The former is an old technology while the latter is a tuner’s favorite. Both offer a number of advantages and disadvantages. Which one should you go for?
What are forced-induction compressors?
Both turbochargers and superchargers are forced-induction compressors. To know which one is better for your application, you need to understand how these devices work.
Forced induction is the delivery of compressed air into a combustion engine’s intake. Unlike a naturally aspirated engine that utilizes atmospheric pressure for oxygen supply, a forced-induction engine uses a compressor to bring up the pressure and density of the air that’s pumped into the engine through the intake manifold.
Turbochargers (also called “turbo”) and superchargers are automotive gas compressors that offer the same benefit: they deliver compressed air that optimizes the combustion process by improving the air-fuel mixture. How these devices work and the way they’re installed are where they differ from each other. Let’s take a closer look.
How does a turbocharger work?
A turbo has two sides: the turbine and the compressor. The turbine wheel is spun by the exhaust gas leaving the engine. A shaft connects the two sides of the turbo, so that when the turbine wheel spins, the compressor wheel is forced to spin as well. The compressor pulls in and pressurizes fresh air from the engine’s air intake.
From there, on most vehicles, the pressurized air is sent to an intercooler. The device cools the air, so that it’s more dense before it enters the engine.
The amount of pressure, also known as boost, the turbocharger creates must be regulated to prevent engine damage. On a traditional turbocharger, typically, this task is accomplished by a wastegate. The wastegate, which is controlled by the car’s computer on modern vehicles, is a valve that diverts exhaust pressure to the exhaust system.
Also, to prevent excess pressure from building up and traveling back to the compressor when the throttle closes, a blow-off valve or compressor bypass valve (CBV) is usually installed at some point before the engine. A CBV quietly routes pressurized air back to the turbocharger. On the other hand, a blow-off valve vents pressure into the atmosphere and is responsible for the turbo flutter sounds we all love.
Types of Turbochargers
Differentiating turbochargers and superchargers should be simple; the former is exhaust-driven while the latter is mechanically driven. However, it could get a little tricky as there are also different types for both. Let’s start by enumerating various configurations of turbos.
1. Single Scroll Turbo
Considered the simplest of all turbocharger configurations, the single-turbo only involves one turbocharger attached to the exhaust. However, it is also the poorest type because it compromises either low-end torque or high-end power. You could either choose to install a small turbo that offers good torque down low but can choke the engine during high RPMs or a larger one that offers more power at higher RPMs. Regardless, there will be a compromise in performance.
2. Sequential (Twin) Turbos
Sequential turbocharging is the way to go if you can’t pick between small and large turbos. This set-up is a combination of small and big turbochargers that compensate good torque at low RPMs and top-end power at high RPMs. The downside is that setting up a small and large turbo is usually expensive.
3. Twin-Scroll Turbo
A twin-scroll turbo uses a divided-inlet turbine housing that keeps the pulses of gases from overlapping when powering the turbo. It also uses a specifically-engineered exhaust manifold. If properly designed, this set-up has the ability to increase low-end torque, boost response, and improve turbine efficiency and fuel economy while lowering gas temperature.
4. Variable Geometry Turbocharger (VGT)
To control the flow of exhaust gases through the turbo, this type of turbocharger uses moveable vanes mounted to a unison ring in the turbine housing. The vanes can be adjusted to change the angle or velocity of flow to the turbine. A computer-controlled actuator is used to adjust vane position. VGT turbos are often used on diesel engines.
At low RPMs, a VGT creates more pressure and velocity to speed up the turbo more effectively, while at high RPMs, the ratio increases to suck in more air. There’s less lag with VGTs compared with other turbocharger set-ups. It should also be noted that VGTs do not need a wastegate for boost control.
5. Variable Twin-Scroll Turbo (VTS)
A VTS combines the benefits offered by a VGT with the advantages of twin-scroll turbos. At low RPMs, one of the scrolls is completely shut to force the air into the other scroll. The valve then opens gradually as the vehicle speeds up, allowing air to pass through the second scroll. In simple terms, you get the power of a twin-turbo set-up at the cost of only having one turbo installed on your engine.
6. Electric Turbo
The latest evolution of turbochargers, the electric turbo is a game-changer. This type of turbocharger includes an electric compressor that provides instant boost to the engine while the turbocharger is still spooling up to power the engine on its own. In short, the electric compressor compensates the turbo lag. Since it is electrically powered, this set-up is trickier to install and implement.
How does a supercharger work?
Unlike a turbocharger, a supercharger is driven off the engine crankshaft. Typically, a belt connects the supercharger to the engine crankshaft pulley. Boost from a supercharger is instantaneous (there’s no lag)—the device is powered the very moment the engine starts turning.
The typical supercharger is mounted on top or in front of the engine to access the crankshaft. An accessory belt is usually wrapped around a pulley connected to the drive gear. When the drive gear rotates, the compressor is engaged. The compressor squeezes the air into a smaller space and spews it into the intake manifold, producing a loud, whining sound that’s usually distinct from the sound of a turbocharger.
Most factory-installed superchargers have a computer-controlled bypass valve. Under certain operating conditions, the valve opens, allowing air to bypass the supercharger and go directly into the intake manifold. Doing this prevents high operating temperatures and improves performance.
Types of Superchargers
For a better comparison between turbos and superchargers, let’s discuss the different supercharger types.
1. Centrifugal Supercharger
A centrifugal supercharger uses impellers to compress air inside the housing. The design looks similar to a turbocharger but the two differ in power source. A centrifugal supercharger is a turbo-shaped forced-induction compressor and its impeller is spun by the crank pulley, not the exhaust gas. This type of supercharger is flexible and more user-friendly because you can change the impeller size and spin it easily at different speeds.
2. Roots-Type Supercharger
The earliest and the father of all supercharger types dates back to the 1840s and is known as the Roots supercharger or Roots blower. The first application of this supercharger was as an air conveyor for mine shafts. A Roots blower features a two- or three-lobe rotor design that produces positive pressure even at a slight throttle input.
Roots blowers are the chrome boxes you typically see sticking out of the hoods of modified muscle cars. They offer far more power in addition to making the vehicle look meaner because they give full-blown power no matter how low or high the RPM is.
3. Screw-Type Supercharger
Roots- and screw-type superchargers may look similar on the outside but they have different configurations inside. A Roots-type pumps air into the engine while a screw design compresses air using twin rotary screws inside. The screws create positive pressure by compressing air through an axial-flow. This helps the compressor stay cool, unlike Roots blowers that heat up.
Turbocharger vs. Supercharger: Pros and Cons
Now, let’s weigh the pros and cons of using a turbocharger and a supercharger to find out which is a better compressor. To compare and contrast the two, we’ll speak about how these devices generally perform or fare in terms of four aspects: lag, efficiency, installation, and power. Bear in mind that the advantages and disadvantages may differ depending on the type of turbo or supercharger you are comparing.
When it comes to lag, generally speaking, superchargers are far more superior than turbos. That’s because the power that superchargers give is more real-time than turbos, as the latter need exhaust gas to pass the turbine first before the compressor can suck in air from the inlet.
Since turbochargers don’t demand engine power to begin air compression, they are considered to be more efficient than superchargers. Superchargers are also known for blowing hot air into the engine when over-boosted. The engine needs more effort to power a supercharger, so more fuel is burned in the process. This drop in fuel economy puts superchargers below turbos in terms of practicality.
The fact that a supercharger is mounted directly on top or in front of the engine makes it simple to install. A turbocharger needs many more components like intercooler piping, a wastegate, and a blow-off valve. Therefore, typically, installing a turbocharger is more complicated than installing a supercharger. And that could be a big factor for people who want quick modifications for increased power.
Generally speaking, superchargers are believed to boost the engine better than turbochargers. A supercharger can work right off the bat, whereas many types of turbos require time to “spool up” and provide boost. So, if you want instantaneous power all the time, a supercharger is the way to go.
Turbocharger vs. Supercharger: The Verdict
Now that we’ve enumerated some of the notable differences between a turbocharger and a supercharger, let’s move on to the verdict. Which between a turbocharger and a supercharger is better? Which one should you install on your car? The answer: It all comes down to preference.
Some people believe supercharged cars are more enjoyable to drive because of the shorter lag, while others argue turbochargers are way cooler both in performance and sound. In reality, however, what gives a car owner more satisfaction could be based on which aspect of performance they think is more valuable. If you like instant launch and don’t worry too much about fuel economy, then the better option would be a supercharger. On the other hand, if installation is not an issue and you care most about efficiency, then go for a turbocharger.
If, however, you still feel undecided after hearing about the various advantages and disadvantages of using a turbocharger or a supercharger, we still have something left in store for you: behold, the twincharger. Twin-charged engines use both a turbocharger and supercharger. Their design allows the supercharger to boost the engine while the large turbo spools. Twin-charging is used on select Volvo engines.