The Basics of Supercharged Cars: How a Supercharger Works
Automotive engineers have strived to boost the power of internal combustion engines ever since their earliest iterations in the late 1800s. Building bigger engines was thought to be the only solution. Larger engines increased the manufacturing and maintenance costs along with the vehicles’ weight. They also minimized fuel efficiency, as evident in muscle cars from the 1960s and 1970s. By the 1980s, manufacturers and gearheads opted for forced induction or supercharger systems instead.
The terms “supercharged” and “turbocharged” are part of the everyday language of cars today. Most drivers associate them with boosted speed or increased power without fully understanding the underlying technologies. Their widespread use has given manufacturers and engineers a way to boost the power in smaller engines while improving fuel economy.
What is a supercharger? What are their pros and cons, and how is supercharging different from turbocharging? Find out in our comprehensive guide to superchargers!
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Supercharger Definition
A supercharger is a forced induction device. The term refers to any device that is mounted to an internal combustion engine. This device forces air into the engine’s combustion chamber. A supercharger is an air compressor that boosts the air intake to gauge pressure (above atmospheric pressure). Each intake cycle receives more oxygen that way. By burning more fuel, it achieves the following:
- Increased power output
- Increased horsepower
- Better fuel economy
Forced Induction
We can split internal combustion engines into three main categories:
- Normally aspirated
- Supercharged
- Turbocharged
Turbocharged and supercharged engines both rely on the principles of forced induction. Naturally aspirated engines use only atmospheric force to drive air into an engine. Forced induction is the process of increasing the density, temperature, and air pressure in an engine with a gas compressor. Both superchargers and turbochargers are “replacements for displacement” devices that provide higher intake force.
Since an engine’s power mainly depends on how much fuel it can burn by taking in more air, forced induction “force-feeds” more air into an engine. That process increases its power and fuel consumption.
Through forced induction, a smaller supercharger motor theoretically gets a similar amount of air that a larger engine would receive. That’s what makes high-performance race cars, muscle cars, supercars, and even economy cars run faster. The power increase depends on how much air the supercharger or turbocharger adds. Both of those devices are compressors, but their operation and performance are different.
How Does a Supercharger Work?
Superchargers are mechanically powered devices. They are bolted-on, engine-driven compressors. They receive energy via an accessory belt or chain linked to the crankshaft. The belt wraps around a pulley and links to a drive gear, which turns the compressor. Superchargers can utilize different drive types, including:
- Belt
- Chain drive
- Gear drive
- Direct drive
Basics of Superchargers, What Does A Supercharger Do?
In a four-stroke engine, one stroke is dedicated to the air intake:
- The piston’s downward movement causes a vacuum;
- This sucks air into the combustion chamber;
- The spark plug ignites the charge, the fuel oxidizes, and there’s an energy release;
- The release gets transferred to the wheels.
The process proves that it’s impossible to increase an engine’s power by pumping more fuel into it. An engine requires a specific amount of air to burn an exact amount of fuel. That equals one part fuel and 14 parts air. It’s necessary to boost the amount of air to increase the amount of fuel, and that’s how superchargers work.
They compress the air to gauge pressure while running on the engine’s power. Without causing a vacuum, they generate power as soon as the driver pushes the accelerator pedal. Since they are driven by the engine, they operate across the whole RPM range. They deliver power with almost no lag. This process also produces a signature mechanical “whine,” an almost addictive noise that many car lovers and gearheads enjoy.
To boost the air intake, it spins at a higher speed than the engine. The drive gear needs to be larger to increase the rotation speed in the compressor. Supercharger cars can reach 50,000–65,000 RPM on average.
If the RPM is 50,000, the compressor delivers a boost of 6–9 pounds PSI. If we consider the 14.7 PSI of sea-level atmospheric pressure, they can boost the air by 50% on average. They also require an intercooler that enables them to reach peak efficiency. The compressed air needs to cool down to increase the air density, thereby increasing the density of the charge that fills the combustion chamber.
Why Do We Need Them?
Forcing air into engines with this method minimizes power derating and produces more power by boosting volumetric efficiency. In turn, they:
- Improve combustion
- Increase fuel efficiency
- Lower emissions
They are useful in hill stations and at high altitudes. A naturally aspirated engine produces less power due to lower atmospheric pressure there. This results in incomplete combustion and a power loss. Forced induction can compensate for that power floss.
Superchargers create abundant amounts of power via a linear power curve and boost that is ideal for street or drag racing. If you want to install one, you have to consider your engine needs, mounting and setup options, and street legal laws.
Supercharger Types
Most drivers associate supercharger kits with Roots-style blowers that bulge out of the engine bay of 1970s muscle cars. The technology has advanced far beyond that, and the current choice of superchargers relies on three main options. The three different types include:
- Roots supercharger
- Twin-screw supercharger
- Centrifugal supercharger
These types direct air into the engine (intake manifold) in different ways.
Roots Type Supercharger
The Roots blower is the oldest supercharger design. It was patented in 1860, but it was used for mine shaft ventilation at the time. It was first utilized in a car in 1900.
These superchargers are large and are installed on top of an engine. They trap large amounts of air inside the pockets of the meshing lobes. They then carry it from the fill to the discharge side in bursts. The air stacks up inside the intake manifold and creates positive pressure. This action is similar to air blowers, and that’s why superchargers received the “blower” nickname.
Since they stick up from the hood, Roots-style blowers are a popular choice for hot rods and muscle cars. The disadvantage is that they increase the vehicle’s total weight and only move air in short bursts. Because of this, the air doesn’t travel in a continuous flow. These two weaknesses reduce the Roots-type effectiveness and make it the less-efficient out of all three types. They have a lower price compared to the other types and are a good fit for racing vehicles due to their quick bursts of extra energy.
Twin-Screw Type
Twin-type superchargers pull air through two meshing lobes. The rotor lobes look like worm gears, and they create pockets that trap the air. This process is similar to the Roots blower.
The compression in twin-screw types occurs inside the housing. The rotors are tapered, which decreases the size of the air pockets as air travels from the fill to the discharge side. That way, there is much less space for air, which increases the efficiency of twin-screw superchargers. This type is more expensive as it takes extreme precision to manufacture the worm gear-like rotors.
Some twin-screw types can also be installed on top of the engine, similar to the Roots-style blower. This type has a high noise floor and requires noise suppression techniques.
Centrifugal Type
This type is the most common as well as the most efficient. Unlike the previous types, centrifugal superchargers mount at the engine’s front. They are attached via a gear or belt drive from the crankshaft. These superchargers feature small dimensions and lighter weight. They are best known for the characteristic “whine” that occurs when you ignite the engine. The satisfying noise can give you a “yee-haw!” moment every time you start your car.
Centrifugal superchargers utilize natural centrifugal force that increases the MAP (manifold air pressure). It contains a rotor-like impeller that spins at rapid speeds of 50,000–65,000 RPM. It pushes air into the compressor housing and draws it towards the hub. It then radiates outward due to centrifugal force.
As the air exits the impeller at high speeds, the pressure remains low. It then gets converted to high-pressure, low-speed air via the diffuser vanes. The air slows down as it reaches the vanes. It allows the engine to burn fuel faster and reach a higher combustion level. The vehicle’s response and speed increase.
Mounting
It’s possible to install any of those types in a vehicle as an aftermarket kit. A qualified mechanic can do this, but you can also install it as a DIY project. Superchargers usually require bolt-on installation, and they install easily on stock pistons, cams, or heads. Car companies can also offer superchargers on production models.
Your choice of supercharger will depend on your engine, requirements, setup options, and the law. Note that the supercharger will need to meet your state’s emission standards and safety inspections.
How Much HP Does a Supercharger Add?
Increased horsepower is the biggest advantage of superchargers. Installing a supercharger can make average trucks or cars perform like larger vehicles with much more powerful engines. If you want to customize your car or don’t have the means to get a new vehicle with a better engine, supercharging is a relatively affordable way to upgrade it. One way to determine how much you want to spend on the customization is to look at horsepower.
They do not increase the horsepower by a flat rate. The horsepower increases in relation to the original horsepower of the engine along with other variables. That’s why manufacturers often list the performance of a supercharger as a percentage increase and within a certain range.
In most cases, a supercharger will provide a 30%–50% power boost on top of the engine’s original output. The downside is that it can take away some of the car’s efficiency by creating drag. Because of that, it boosts horsepower by roughly 46% of the engine’s original specifications. The performance will also depend on the type, its installation, and the vehicle’s overall operating condition.
A supercharger can deliver a 6–9 pound boost on average. If we consider a 300 horsepower engine (unmodified) and boost it by 7 pounds, the result will equal approximately 450 cubic inches or 450 horsepower. Adding other mods, like an upgraded exhaust system or an intercooler, will work together with the supercharger and maximize its potential. With higher initial horsepower, the power increase will be boosted even further.
What Are Turbochargers?
While superchargers are engine-driven, turbochargers operate on exhaust gasses. Turbochargers were once considered an essential modification for tuned-up 1980s race cars, but they are now common in all types of production vehicles. Most turbochargers operate via a:
- Compressor
- Turbine
- A pair of fans
Exhaust gas travels through a tube before reaching the turbine. The turbine is located in the exhaust steam while the compressor rests in the air intake. Since the compressor is linked to the turbine, it spins along with it, enabling the compressor to increase the air intake rate. In turn, the engine speeds up.
What’s the Difference Between Turbochargers and Superchargers?
The main difference is in the energy source. Superchargers receive energy mechanically via a belt drive. Turbochargers receive energy from exhaust gasses. Like superchargers, turbos also rely on forced induction but receive gasses after they exit the engine. They don’t depend on the crankshaft and are more efficient for low RPM driving. This difference comes into play mainly with smaller engines found in compact and economy cars.
Another major difference relates to lag. Turbochargers create turbo lag because they can’t kick in until enough exhaust gasses are released. This creates a noticeable lag between the moment you press the gas pedal and the moment the engine reaches a sufficient RPM that can engage the compressor. That is why turbochargers generate less power. They utilize less gas at low RPMs. Superchargers operate without lag.
Why Do Production Vehicles Favor Turbos?
Turbochargers use exhaust gases, and that’s how they use energy that would have gone to waste otherwise. They do not consume as much engine power compared to superchargers. This advantage makes them ideal for smaller engines in production vehicles and economy cars.
Turbochargers get better results during FTP-75 fuel-economy tests that determine CAFE ratings for car corporations. Vehicle manufacturers like Volvo use both devices in their newest vehicles. They use twin charging. A supercharger increases the off-the-line acceleration and switches to the turbo once it charges up.
Even though turbos are more common in production cars, supercharger engines also have their merits. Their lack of lag makes them ideal for v8 supercharger engines like the Dodge 440 V8.
Superchargers vs. Turbochargers
The table below outlines the differences between supercharged and turbocharged engines:
Supercharger | Turbocharger |
Gains energy from the crankshaft | Gains energy from the exhaust stream |
Provides a continuous energy supply | Provides a discontinuous energy supply |
Connects to the engine directly via a belt | Does not connect to the engine |
Emits smog | Contains smog-reducing equipment that lowers carbon emissions |
Spins at speeds up to 50,000–65,000 RPM | Spins at speeds up to 15,000 RPM |
Produces instant power without lag | Generates lag but provides increased power at higher speeds |
Does not require an intercooler as the air has a lower temperature | Requires an intercooler as the air has a higher temperature |
Supercharger Pros and Cons
If you’re considering a supercharger, the following table shows its key benefits and disadvantages:
Supercharger Pros | Supercharger Cons |
Increased power output | Reduced engine power |
Reduced emissions from gases | Turbochargers lower carbon emissions more effectively |
Ideal for sports and race cars; quick acceleration without lag | Not ideal for all drivers; turbochargers produce lag, which may be better for lower RPMs |
Affordable and easy to install | Increased thermal stress |
Increased torque output across the entire speed range | Increased stress in the cylinder could cause damage |
Why You Should Supercharge Your Car
If you are looking to expand the power of your engine, you can supercharge your car for street use, towing, and drag racing. Quarter Mile Addiction offers a diverse range of supercharger kits suitable for all types of vehicles. Supercharging your car will deliver high performance along with rapid speed boosts that maximize the power of your engine!
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