Turbochargers and superchargers can sometimes get confused. However, there are a few significant differences that put them on opposite ends of the automotive spectrum. Before discussing their differences, it helps to understand what links turbochargers and superchargers from an engineering standpoint. Turbochargers and superchargers are forced induction systems. These systems use compressors to push compressed air into the engine. The compressed air allows for extra oxygen to reach the engine, which helps create an extra boost of power.
Like the Roots supercharger, the air inside a twin-screw supercharger is trapped in pockets created by the rotor lobes. But a twin-screw supercharger compresses the air inside the rotor housing.
That's because the rotors have a conical taper, which means the air pockets decrease in size as air moves from the fill side to the discharge side. As the air pockets shrink, the air is squeezed into a smaller space. This makes twin-screw superchargers more efficient, but they cost more because the screw-type rotors require more precision in the manufacturing process.
Some types of twin-screw superchargers sit above the engine like the Roots supercharger. They also make a lot of noise. The compressed air exiting the discharge outlet creates a whine or whistle that must be subdued with noise suppression techniques.
A centrifugal supercharger powers an impeller — a device similar to a rotor — at very high speeds to quickly draw air into a small compressor housing. Impeller speeds can reach 50, to 60, RPM.
As the air is drawn in at the hub of the impeller, centrifugal force causes the air to radiate outward. That means the air leaves the impeller at high speed but low pressure. A diffuser — a set of stationary vanes that surround the impeller — converts the high-speed, low-pressure air to low-speed, high-pressure air. Air molecules slow down when they hit the vanes, which reduces the velocity of the airflow and increases pressure.
Centrifugal superchargers are the most efficient and the most common of all forced induction systems. They are small, lightweight and attach to the front of the engine instead of the top. 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.
Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Under the Hood. As government legislation and environmental concerns drive a shift away from fuel-thirsty big-displacement naturally aspirated engines toward smaller thriftier ones, automakers are increasingly employing turbochargers and superchargers to make more power from less fuel.
Both devices serve as a "replacement for displacement" by helping cram the same amount of air a bigger engine would naturally inhale into a smaller engine so they can make the same power when the driver's foot hits the floor.
Oxygen, it turns out, is way harder to get into an engine than fuel. This is also the purpose nitrous-oxide systems serve in the go-fast aftermarket. Let's take a fresh look at the relative merits of turbocharging versus supercharging. The earliest superchargers were all driven by power taken from the crankshaft, typically by gear, belt, or chain.
A turbocharger is simply a supercharger that is powered instead by a turbine in the exhaust stream. The first of these, dating to , were referred to as turbosuperchargers and were employed on radial aircraft engines to boost their power in the thinner air found at higher altitudes.
That name was first shortened to turbocharger and then to turbo. Each can be used to increase power, fuel economy, or both, and each has pros and cons.
Turbochargers capitalize on some of the "free" energy that would otherwise be completely lost in the exhaust. Driving the turbine does increase exhaust backpressure, which exerts some load on the engine, but the net loss tends to be less by comparison with the direct mechanical load that driving a supercharger involves the biggest blowers powering a top-fuel dragster consume crankshaft horsepower in an engine rated at 7, total horsepower.
But superchargers can provide their boost almost instantly, whereas turbochargers typically suffer some response lag while the exhaust pressure required to spin the turbine builds.
Clearly a top-fuel dragster trying to run the quarter in four seconds has no time to waste waiting for exhaust pressure to build, so they all use superchargers, while vehicles tasked with boosting a company's corporate average fuel economy CAFE can't afford to squander precious horsepower on blowers, so they mostly use turbos. But with the rise of mild hybridization and volt electrical systems, you can expect to see greater use of superchargers driven by freely recuperated electricity stored during deceleration and braking.
Mercedes-Benz's new M six-cylinder now arriving in vehicles like the CLS and GLE uses just such a system, as does the similarly sized and configured range-topping engine in the new Land Rover Defender. Above we noted that the amount of oxygen that an engine can "breathe" is the limiting factor as to how much power it can produce, because fuel-injector technology is more than capable of supplying as much fuel as can possibly be burned with the amount of oxygen in the cylinder.
Naturally aspirated engines operating at sea level get air at It doesn't usually work out that way. Compressing intake air adds heat, which along with the added pressure increases the likelihood of engine-damaging pre-detonation or "ping," so the timing often has to be retarded somewhat.
This can limit the amount of time the fuel has to completely burn, and hence erodes some of the power gain. In the end, the typical expectation is that adding 50 percent more air yields 30 to 40 percent more power.
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