Turbos and Superchargers: What Is the Difference?
Dissatisfied with the power of your internal combustion engine? Have you considered fitting a turbo or a supercharger?
Trust us, you will not be disappointed with the results. Read on to find out why.
What is a supercharger?
Superchargers are special devices used in internal combustion engines to help increase the power output of the engine. They work, in effect, like a kind of compressor or blower, and are used to increase the intake manifold pressure of and thus the power of the engine.
An intake manifold, in case you are not aware, is another specialist part of the engine that ensures that incoming air is distributed evenly to the combustion cylinders. Intake manifolds also have a secondary purpose of cooling down the cylinders to help prevent engine damage from overheating.
Superchargers can come in different configurations, including root, twin screw, TVS, and centrifugal.
On average, a supercharger may add a horsepower boost of around 45 percent of the engine's original specs, and increase torque by around 30 percent. They also tend to increase the engine's fuel efficiency as the combustion process is more efficient.
Superchargers tend to be used in racing cars or vehicles that need to pull heavy loads.
How does a supercharger work?
As previously mentioned, a supercharger is used to artificially increase the pressure (density) of incoming air into an internal combustion engine.
Most superchargers are driven by a belt connected to the crankshaft. This, in turn, rotates the compressor, which draws air in, compresses it, and then discharges it into the intake manifold.
To pressurize the air, a supercharger spins very rapidly - at speeds as high as 50,000 to 65,000 rotations per minute (RPM), adding about 50 percent more air into the engine.
As the air is compressed, it also gets hotter. This makes it less dense so that it does not expand as much during the explosion in the engine and can't create as much power when ignited by the spark plug. So, the compressed air must also be cooled before it enters the intake manifold. An intercooler unit is used to cool the air by running it through a system of air or water-cooled pipes or tubes, like a radiator. The reduction in air temperature increases the density of the air as it enters the combustion chamber.
By having a higher amount of oxygen present, more fuel can be burned per cycle of the engine which, in turn, drastically improves the work the engine can perform and the overall power output of the engine.
In aircraft engines, superchargers are primarily employed to compensate for the relatively thinner atmosphere at altitude and, therefore, improve the power of an internal combustion engine during flight.
Superchargers can be powered in a variety of ways, but the most common is via mechanical means by belts, gears, shafts, or chains powered by the main engine's crankshaft.
Is a supercharger reliable?
You probably won't be surprised to find out that by increasing the amount of fuel burned in a given period of time, the internal temperature of an engine can increase significantly. Over time this can lead to premature wear and tear on sensitive parts of the engine.
For this reason, superchargers, like all forced induction systems, can shorten the useful lifetime of an internal combustion engine.
But that is not the only downside to them. They also tend to parasitically draw off power from the engine, while simultaneously increasing the net power of the engine.
That being said, there are some inherent pros to superchargers too. By being powered directly from the drivetrain, they provide no lag and offer consistent increased power delivery.
They are also a quick and relatively easy way to increase an engine's horsepower and tend to be a relatively cheap solution to the problem.
What is a turbocharger?
Turbochargers, or turbosuperchargers, are a relatively newer and more efficient forced air induction device for internal combustion-engined vehicles. Technically a form of the supercharger, turbos are effectively gas-powered compressors.
They are designed to help improve the overall efficiency of the engine and noticeably increase its performance.
It is for this reason, that more and more automakers are now fitting them as standard on many of their cars, and particularly on diesel engines. An engine’s precise power and power to weight ratio can be noticeably bumped up by turbocharging.
They first came into use around the mid-1910s and were referred to as turbosuperchargers. These early "turbos" were employed on radial aircraft engines to boost their power in the thinner air found at higher altitudes. That name was later shortened first to turbocharger, and then to "turbo", as they are more commonly referred to today.
Turbos can provide an impressive increase in engine power and torque by around 20% to 30%. Under certain conditions, this can be increased to as much as 50% at an engine's peak capacity.
How does a turbocharger work?
Turbochargers, like their ancestors the superchargers, artificially increase the density/pressure of intake air to provide a higher air to fuel mix in the engine's cylinders. Unlike superchargers, turbochargers are powered using the exhaust gases of the engine.
This is achieved via the special design of the turbocharger. Each one consists of two main halves that are connected together by a shaft. One side of the turbocharger receives the hot exhaust gases that are then used to spin a turbine, and the connecting shaft. This is often called the "turbine section".
This shaft then turns another turbine in the other half of the turbocharger, called the "compressor section", to suck in and pressurize intake air before delivery to the engine's combustion cylinders. It is this compression of intake air that provides the engine a boost in power and fuel efficiency because more air is available during the combustion process.
This, in turn, means more fuel can be added by cycle and, therefore, more power is generated.
Because of the way they are powered, turbochargers are often referred to as providing "free power" to the engine. Like superchargers, they are also often fitted to aircraft engines, where they can increase the efficiency of engines at the relatively thinner atmosphere at altitude.
It is important to note that while they do improve the fuel efficiency of an engine, this is only the case when the engine has been designed to accommodate one. Automakers generally fit smaller engines with a turbocharger to provide the same power output, but lower fuel consumption, than larger engines.
By way of example, let's take a 2.5 liter (84 oz) inline-4 cylinder naturally aspirated engine. If you decreased its displacement to 1.4 liters (47 oz) and then turbocharged it, the resulting engine would have the same, of not better, performance, and use a fraction of the fuel.
What are the cons of turbochargers?
Turbochargers are awesome pieces of kit, but they are not without their problems. The main issue being the heat they generate.
As they are powered by hot exhaust gases from the engine, they tend to get very hot, very quickly -- especially when the engine is pushed to its limits. However, there are ways to compensate for this, like providing extra cooling vents around the turbocharger.
Another issue with turbochargers is that they can suffer from lag. This is the delay between increasing the throttle (demanding more power) and actually receiving the boost you are looking for.
This is especially true when the engine's speed is low, as there is not a lot of exhaust gas being passed to the driving half of the turbocharger. For this reason, some time is needed to get the turbocharger up to speed.
What is the difference between a turbocharger and a supercharger?
You've probably gained an appreciation of the differences between them by now, but for ease of reference, the main differences between the two include: -
- Superchargers have no lag, while turbochargers do. This is due to the inherent way in which either device is powered. The former is driven directly by the engine's driveshaft, while the latter uses exhaust gases from the engine for power. Manufacturers of turbos have been working tirelessly over the year to reduce "turbo lag" but it is still noticeable.
- Superchargers are less efficient overall. As they siphon off power from the engine, they do not offer the same "payback" as a turbocharger.
- Superchargers tend to run at lower temperatures when compared to turbochargers. This is primarily because turbos use hot exhaust gases from the engine.
- Both turbos and superchargers tend to require intercoolers for optimal performance. These components are used to cool the incoming air before it enters the engine. Cooler intake air means better performance, generally speaking.
- Superchargers are relatively easier to install than turbos, they are also better suited for engines with smaller displacements.
- Turbos are relatively more complex to install and are best suited for engines with larger displacements.
What is more efficient: a supercharger, or a turbocharger?
The answer to this depends, ultimately on the engine in question. As previously mentioned, for smaller engines a supercharger is usually the best choice, and vice versa for larger engines.
That being said, automakers tend to fall on side of the turbocharger. They have determined that turbos are the better choice, especially when considering fuel efficiency. Turbos have enabled automakers to replace many of their V-6 engines with more efficient inline fours to provide an equivalent amount of power.
But, this might only be a temporary dominance for the turbo. A new kind of supercharger has recently reared its beautifully engineered head -- the electric supercharger.
These superchargers comprise electrical motors used to spin a compressor to provide a burst of low-rpm torque to the engine. They can be found on some modern models of cars like the 2019 Mercedes-AMG CLS53, and E53.
While an exciting development, the market will likely be dominated by turbos for some time to come.