Louis Renault designed the centrifugal supercharger in , which is a noticeable departure from either a Roots or twin-screw. First, an impeller is powered to 50,, rpm to draw air into the housing, where centrifugal forces cause it to radiate from the center.
Then the air is passed through a diffuser — a series of vanes on the perimeter of the impeller — to pressurize it before it reaches the intake manifold. The advantages of a centrifugal supercharger are its compact size, low weight, and convenient positioning on the front of the engine.
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While both superchargers and turbochargers increase engine power, each has pluses and minuses. Superchargers offer a robust initial response because they're connected directly to the engine's crankshaft. The direct connection causes them to wind up faster and feed pressurized air into the intake instantaneously. But because of their direct link to the engine, they create parasitic loss and are less efficient than turbochargers.
Today's advanced turbocharged engines approach supercharged engines in their low-RPM response but benefit from being more efficient. Because exhaust gases power a turbocharger, it doesn't sap power from the motor while building boost. The drawback of a turbocharger is delayed power off the line while the turbine spools up. Whether you're looking for a supercharged set of wheels or something more economical , Shift has you covered.
When you buy a used car from Shift, a certified mechanic performs a point inspection, ensuring your vehicle is in top condition when you drive away. Shift also offers free vehicle history reports, so you know your car is good to go from the get-go. A supercharged engine has several benefits when compared to a naturally aspirated version. Increased horsepower and torque are the most obvious. Extra oomph off the line is a nice feature to have whether you're driving through the city or traveling through the countryside.
In the case of a centrifugal supercharger, you're getting a smaller engine to produce power similar to a larger one while still achieving good fuel economy.
A centrifugal supercharger's clean design and placement mean your car has the same flat hood and open engine bay as any other. Then there's the sound. You have to hear it to understand it. The same way a high-performance engine sings all the right notes, a supercharger spinning at 50, rpm lets out a noise that's racy and innovative all at once.
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But bigger engines, which weigh more and cost more to build and maintain, are not always better. Another way to add power is to make a normal-sized engine more efficient.
You can accomplish this by forcing more air into the combustion chamber. More air means more fuel can be added, and more fuel means a bigger explosion and greater horsepower. Adding a supercharger is a great way to achieve forced air induction. A supercharger is any device that pressurizes the air intake to above atmospheric pressure. Both superchargers and turbochargers do this. Turbochargers are powered by the mass-flow of exhaust gases driving a turbine.
An ordinary four-stroke engine dedicates one stroke to the process of air intake. There are three steps in this process:. Once air is drawn into the engine, it must be combined with fuel to form the charge — a packet of potential energy that can be turned into useful kinetic energy through a chemical reaction known as combustion.
The spark plug initiates this chemical reaction by igniting the charge. As the fuel undergoes oxidation, a great deal of energy is released. The force of this explosion, concentrated above the cylinder head, drives the piston down and creates a reciprocating motion that is eventually transferred to the wheels.
Getting more fuel into the charge would make for a more powerful explosion. This chemically correct mixture — 14 parts air to one part fuel — is essential for an engine to operate efficiently. The bottom line: To put in more fuel, you have to put in more air.
Superchargers increase intake by compressing air above atmospheric pressure, without creating a vacuum. Supercharging adds an average of 46 percent more horsepower and 31 percent more torque. In high-altitude situations, where engine performance deteriorates because the air has low density and pressure, a supercharger delivers higher-pressure air to the engine so it can operate optimally. Unlike turbochargers, which use the exhaust gases created by combustion to power the compressor, superchargers draw their power directly from the crankshaft.
Most are driven by an accessory belt, which wraps around a pulley that is connected to a drive gear. The drive gear, in turn, rotates the compressor gear. The rotor of the compressor can come in various designs, but its job is to draw air in, squeeze the air into a smaller space and discharge it into the intake manifold. To pressurize the air, a supercharger must spin rapidly — more rapidly than the engine itself. Making the drive gear larger than the compressor gear causes the compressor to spin faster.
Superchargers can spin at speeds as high as 50, to 65, rotations per minute RPM. A compressor spinning at 50, RPM translates to a boost of about six to nine pounds per square inch psi. Atmospheric pressure at sea level is As the air is compressed, it gets hotter, which means that it loses its density and can not expand as much during the explosion. For a supercharger to work at peak efficiency, the compressed air exiting the discharge unit must be cooled before it enters the intake manifold.
The intercooler is responsible for this cooling process. Intercoolers come in two basic designs: air-to-air intercoolers and air-to-water intercoolers. Both work just like a radiator, with cooler air or water sent through a system of pipes or tubes. As the hot air exiting the supercharger encounters the cooler pipes, it also cools down. The reduction in air temperature increases the density of the air, which makes for a denser charge entering the combustion chamber.
There are three types of superchargers: Roots, twin-screw and centrifugal. They also make a distinctive whine as the engine revs up — a quality that may turn heads out on the street. Any of these superchargers can be added to a vehicle as an after-market enhancement. Several companies offer kits that come with all of the parts necessary to install a supercharger as a do-it-yourself project. In the world of funny cars and fuel racers, such customization is an integral part of the sport.
Several auto manufacturers also include superchargers in their production models. The biggest advantage of having a supercharger is the increased horsepower. Attach a supercharger to an otherwise normal car or truck, and it will behave like a vehicle with a larger, more powerful engine.
But what if someone is trying to decide between a supercharger and a turbocharger? This question is hotly debated by auto engineers and car enthusiasts, but in general, superchargers offer a few advantages over turbochargers. Superchargers do not suffer lag — a term used to describe how much time passes between the driver depressing the gas pedal and the engine's response. Turbochargers suffer from lag because it takes a few moments before the exhaust gases reach a velocity sufficient to drive the turbine.
Superchargers have no lag time because they are driven directly by the crankshaft. Roots and twin-screw superchargers, for example, provide more power at lower RPM. Centrifugal superchargers, which become more efficient as the impeller spins faster, provide more power at higher RPM.
Installing a turbocharger requires extensive modification of the exhaust system, but superchargers can be bolted to the top or side of the engine.
That makes them cheaper to install and easier to service and maintain. For decades, turbocharged cars had to idle for about 30 seconds before being shut down so that they could cool properly. But modern turbos have automated systems that handle that for you, so you can treat a turbocharged engine like a regular engine — or a supercharged engine.
With that said, a good warmup is important for superchargers, as they work most efficiently at normal operating temperatures. Superchargers are common additions to the internal combustion engines of airplanes. This makes sense when you consider that airplanes spend most of their time at high altitudes, where significantly less oxygen is available for combustion.
With the introduction of superchargers, airplanes were able to fly higher without losing engine performance. Superchargers used with aircraft engines work just like those found in cars. They draw their power directly from the engine and use a compressor to blow pressurized air into the combustion chamber.
The illustration above shows the basic setup for a supercharged airplane. The biggest disadvantage of superchargers is also their defining characteristic: Because the crankshaft drives them, they must steal some of the engine's horsepower. A supercharger can consume as much as 20 percent of an engine's total power output. But because a supercharger can generate as much as 46 percent additional horsepower, most think the trade-off is worth it.
Supercharging puts an added strain on the engine, which needs to be strong to handle the extra boost and bigger explosions. Most manufacturers account for this by specifying heavy-duty components when they design an engine intended for supercharged use.
This makes the vehicle more expensive. Superchargers also cost more to maintain, and most manufacturers suggest high-octane premium-grade gas. Despite their disadvantages, superchargers are still the most cost-effective way to increase horsepower. Superchargers can result in power increases of 50 to percent, making them great for racing, towing heavy loads or just adding excitement to the typical driving experience.
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Under the Hood. Engine Performance. How Superchargers Work. Troy Coughlin, Jr. Many race cars have supercharged engines. David J. Supercharger Basics " ". Photo courtesy Muscle Mustang. The piston moves down. This creates a vacuum inside the cylinder. The vacuum causes air at atmospheric pressure to be sucked into the combustion chamber. Roots Superchargers " ".
You sometimes see a roots supercharger sitting on top of the hood of a drag car. Twin-screw Superchargers " ". Centrifugal Superchargers " ". Supercharger Advantages " ". Supercharger Disadvantages The biggest disadvantage of superchargers is also their defining characteristic: Because the crankshaft drives them, they must steal some of the engine's horsepower.
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