What Is A Supercharger?

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How does a supercharger work and why do we use them?

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Have you ever heard the expression "there's no replacement for displacement"? Well, it used to be true. Naturally aspirated engines used to be the only kind, and you needed more capacity to produce more power. As the earliest way of improving performance, it was the most common. But now we have forced induction, which is the term given to a system that increases intake air pressure above that of the ambient atmospheric pressure. The most common type of forced induction on a vehicle these days is turbocharging, but another way of doing this is by means of a supercharger. How does a supercharger work though, and what kinds of superchargers are there? In this article, we'll give you a crash course on superchargers and dwell briefly on some of the fantastic cars that use this technology.

Supercharger Mercedes-Benz

What is a Supercharger?

What is a supercharger, and what does it do? Basically, a supercharger is an air compressor. Its purpose is to increase the pressure or density of air supplied to an internal combustion engine much like a turbocharger. With more air, the engine can also add more fuel, thus doing more work and producing more power. The supercharger itself can be powered and give power by means of either a belt, shaft, or chain connected to the crankshaft of the engine. The downside is that superchargers sap power from the engine before they produce any themselves. Technically, all turbine systems including turbos (turbosuperchargers) fall into the supercharging category, but these days, superchargers are generally only called such when they are mechanically driven via the aforementioned belt/shaft/chain.

How Does a Supercharger Work?

Although there are various types of superchargers, the purpose of each is the same: to increase air pressure as it enters the engine. This is especially useful in aviation, where air at high altitudes is particularly thin, but any engine can unlock more performance if it gets more air pressure with more oxygen and more fuel. Much like a turbo, increasing density is the goal. However, while turbochargers scavenge exhaust gasses that would otherwise be wasted, a supercharger tends to sap power from the engine before it produces any, as it is connected to the crankshaft and cannot be started without it. Once the supercharger has started spinning, it pumps denser air into the engine, which starts producing more power with more air and fuel, but until then, the blower is actually drawing power. The upside is that it takes very little time for the supercharger to speed up, so throttle response remains excellent and the power feels like it is always available. However, superchargers can cause a spike in temperature, and if these temperatures get too high, detonation can occur. Fortunately, you can fit an intercooler as you would with a turbo, thus reducing intake temps and increasing density. Before we go into this any further, we have to stop with the generalizations and consider the different types of superchargers out there.

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Work of Supercharger BMW

Types of Superchargers

With turbochargers, there are also various types, but they all work in relatively similar ways; you can read up on everything turbocharger-related here. With superchargers, the different types have more diverse methods of doing their job (a screw supercharger is very different from a centrifugal supercharger), but the end goal remains the increase of air pressure as it enters the intake of the engine. Two main types of superchargers will be considered (although less common variants exist as well) but we will list some of the subcategories too.

  • Positive Displacement: The positive displacement supercharger is the most common kind and has sub-types that include the Roots, Lysholm twin-screw, sliding vane, and scroll-type, which is also known as the G-Lader. The Roots-type blower is the oldest of the various types out there and is one of the simplest. Furthermore, it can be very effective at developing positive intake manifold pressure at low engine speeds, thus sacrificing very little in the way of throttle response. But what you really need to know is the basic principles of positive displacement, not how each type of supercharger works.
    Two subcategories for positive displacement superchargers are internal and external compression types. External compression 'chargers transfer air at ambient pressure, so while the supercharger is boosting, the air inside the supercharger remains at ambient pressure and only air downstream of the supercharger is compressed. Subsequently, these superchargers are very good at moving air at low-pressure differentials. Ultimately, however, positive displacement superchargers work in a linear fashion, so boost at 2,000 rpm is doubled when the engine reaches 4,000 rpm. This is good for consistency but means that low-down, you may not have as much power as you would like.
    Internal compression refers to the air pressure within the supercharger itself. This air pressure is already at, or close to, boost level and can be delivered in a smooth manner with little or no backflow. Internal compression superchargers use a fixed internal compression ratio, so when the boost pressure is equal to the compression pressure of the supercharger, you get zero backflow. Of course, if the boost pressure rises beyond its target, then you can still get backflow as with a Roots supercharger, but the internal compression ratio of this kind of supercharger can be matched to the targeted boost pressure to optimize mechanical efficiency and rarely deviates above this without errors in tuning. As you can see, extracting more out of it can be tricky, so this type of supercharger is less suitable for high-horsepower applications, but throttle response is noticeably better here.
  • Dynamic: Dynamic compressors accelerate the air to a high speed and then exchange that velocity for pressure by diffusing (slowing down) the air. The most common type in the automotive industry is the centrifugal supercharger, which looks very much like a turbocharger. As the name suggests, it uses centrifugal force to generate pressure, and like a turbo, that centrifugal force is generated by a spinning turbine. In a turbocharger, this turbine is spun by waste exhaust gasses, while in a centrifugal supercharger, the turbine is driven by a belt that is connected to the crankshaft. Various pulley sizes and belt types can alter the level of performance you receive, just as bigger turbine wheels and housings can help a turbo to produce more power. However, like a turbo, the centrifugal supercharger needs to build boost, which it does with the speed of the engine's crankshaft. As a result, you get more power the faster the engine is operating, but this means that you put more strain on the engine and have less power at low rpm. Of course, different sizes of turbines, belts, and pulleys can affect the capacity of the supercharger to pressurize air, but the bottom line is that superchargers like this still do their best work at high rpm, which can exceed 100,000 rotations a minute.
Supercharger Components Mercedes-Benz

What are the Benefits and Disadvantages of Superchargers

Pros and Cons

  • Great throttle response
  • Relatively linear power delivery
  • Relatively simple to install
  • Minimal additional hardware required
  • Fairly reliable
  • Whining noise sounds awesome to some
  • Power is sapped before it is produced
  • Differing altitudes can negatively impact performance
  • Whining noise is annoying to some
  • Tricky to tune correctly
  • Generally more expensive than turbochargers
  • Poor fuel consumption

Supercharged Cars

If you're reading this, you probably have an interest in supercharged engines and already know some of the models out there, whether that's your favorite muscle car or one of the more high-end supercars. Here we'll list some commonly known supercharged cars and sports cars, as well as some unusual cars from the past and the present that have used superchargers.

  • 2020 Dodge Challenger SRT Hellcat
  • 2020 Ford Mustang Shelby GT500
  • 2021 Jaguar F-Type
  • 2005 Mercedes-Benz C230 Kompressor
  • 2020 Lotus Evora GT
  • 2009 Audi S4
  • 2021 Chevrolet Camaro ZL1
  • 2021 Volvo XC90 T6
  • 2003 Mercedes-Benz E55 AMG
  • Jaguar C-X75 Concept
Dodge Challenger SRT Hellcat Dodge
Supercharger Jaguar CarBuzz
Jaguar F-Type CarBuzz

Conclusion

There's much to be said for superchargers and the advantages they bring to the performance of your car, although lowering fuel economy and upping the MSRP are some negatives to consider, too. Still, some of the best high-performance vehicles out there are supercharged. We also elaborate on the differences between turbocharging and supercharging in our blog post, here.

FAQs about Supercharged Cars

What is supercharger capacity?

You'll often hear of superchargers being referred to by their capacity, much like an engine. For example, the Dodge Challenger SRT Demon has a 2.7-liter supercharger. Simply put, this capacity refers to the volume of air that the supercharger can push into the engine with each rotation. Thus, supercharger capacity ratings are given in liters per revolution or cubic inches per revolution.

Is a supercharger better than a turbocharger?

It depends on the size, type, and application, but each of these systems has its drawbacks and advantages. That said, turbos are generally easier to package, weigh less, and are more efficient. They are also easier to tune and cost less to replace.

Can you put a supercharger on a diesel engine?

Yes, but they are less efficient than turbocharged diesel engines. With the main focus of diesel engines (after their torque) being fuel economy, supercharged diesels are not common.

What engine type is most commonly supercharged?

Generally, a supercharged V8 is the kind that you'll be most likely to have come across, although there have been numerous supercharged V6 models and even supercharged inline engines. The reason for this is the wealth of low-end torque produced by a V8, which helps offset the power sap that a supercharger causes at very low rpm. V8s also displace a lot of air, and the more air there is to compress, the more impressive the effects of the supercharger will be - assuming that the supercharger is right for the application, of course.

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