Superchargers and turbochargers, or turbos, are more common on production vehicles than ever before in the history of the automobile. A turbocharger and a supercharger are both types of forced air induction systems, which compress air–and fuel, in some cases–before it is sent to the intake manifold and delivered to the engine for combustion. This increases not only the pressure, but also the density and the temperature of the incoming air. These systems are designed to force more air into the engine, which boosts performance and aids in efficiency. Both superchargers and turbos are designed to achieve the same result, but the way in which they accomplish forced air induction is where they differ. Read on to learn more about superchargers and turbos, and what benefits each option may provide for your engine.
How Does a Supercharger Work?
Though the term “supercharger” can technically be used to describe any air compressor that forces air into the engine, typically superchargers in the automotive world are distinct from turbochargers in how they are powered. Superchargers are mounted to the intake manifold and designed to use direct mechanical energy from the engine’s crankshaft to turn internal turbines that pressurize air. The supercharger’s power comes from a belt, chain, or gear that is turned by the engine while it is running. Superchargers, also called “blowers” in the automotive community, are a popular add-on performance accessory on many hot rods and drag cars, and their increased deck height offers a distinctive look that often includes modifying the hood to allow the assembly to pass through.
In recent years, superchargers have become less common than turbochargers on production vehicles, but there are still a multitude of examples of factory supercharger-equipped engines across domestic and import automotive manufacturers. Though they supply added performance and efficiency, superchargers do have one pitfall – they still have to draw power from the engine. This means that factory-equipped superchargers have also been called a “replacement for displacement” – meaning that they allowed smaller engines to generate the horsepower of traditional high-displacement engines, and they allowed the vehicle to use less fuel to generate power.
What is the Difference Between a Supercharger and Procharger?
Though a supercharger and a procharger effectively do the same job in a very similar way, there are a few small differences that may make one option more suitable for your application. Both superchargers and prochargers run off of a belt attached to the crankshaft, and by nature are less likely to experience lag than a turbo. But superchargers utilize bursts of air sent to the engine as they run through their compression cycle to increase performance, while prochargers deliver a consistent flow of pressurized air to the intake. They accomplish this by drawing air in with a centrifugal force, and then pushing the compressed air out to the intake continuously. This provides smoother response and minimizes lag as the engine changes RPM. Superchargers are also typically taller and may require modifications to be made to your hood to make them fit, while prochargers are usually more compact. The final difference worth noting is that prochargers are often considerably more expensive, and may also produce more noise during operation than most superchargers.
How Does a Turbocharger Work?
Turbochargers, commonly called “turbos”, accomplish the same goal as a supercharger while utilizing power that would otherwise be wasted – exhaust pressure. Turbos are designed with two sets of ports separated by a turbine, and are designed to use the pressure generated by the exhaust traveling through one set of ports to pressurize air traveling through the other side of the assembly. This pressurized air is then sent to the intake while the exhaust continues through the rest of the emissions system and exits the vehicle. The amount of air pressure fed to the engine, also called “boost”, depends entirely on the amount of exhaust pressure being fed through the turbo, and a blowoff valve is equipped in turbocharged systems to allow excess pressure to be released to prevent damage to the engine.
The increase in efficiency and performance from a turbocharger makes them a perfect candidate for OE-installed engines, but two factors should still be considered. Though they add a considerable amount of performance using “free” energy from the exhaust that would otherwise be lost, engines equipped with a turbo can suffer a slight loss of power due to an increase in exhaust backpressure. This does not negate the value of a turbo, but it is important to note that the true power increases of a turbo will have a minor reduction due to pressure buildup in the engine because the turbo is an obstacle in the exhaust system. Turbos also react more slowly than superchargers, which deliver near-immediate power, but this is likely imperceptible in most passenger vehicles. The “turbo lag” is why most drag racing vehicles have traditionally utilized superchargers over turbochargers, because the immediacy of air induction makes a supercharger ideally-suited for quick times off the line.
Supercharger vs Turbocharger - Pros & Cons
This is a difficult question to answer without knowing how the vehicle will be used. Superchargers produce a lot of power, but they may limit increases in efficiency due to power demands on the engine. Every accessory connected to the belt drive or gear drive of the engine requires some amount of power to run, which may affect fuel mileage. This is often less of a concern in performance applications, and superchargers feature improved throttle response over turbochargers which can shave precious tenths of a second in drag racing applications. Superchargers are also typically more reliable and maintenance-free, but may not produce the large power gains a turbo could achieve.
There is a reason that so many modern small displacement production vehicles are equipped with turbochargers – they deliver power without sacrificing much, if any, fuel efficiency. Smaller displacement engines help keep vehicles light, which is an important consideration for vehicle manufacturers who must adhere to CAFE (corporate average fuel economy) standards. Even though turbo systems add some weight, they are often more compact than superchargers and deliver added power while minimizing the load on the engine. The most notable downside to turbocharging in performance applications is “turbo lag”. Turbo lag refers to a delay between acceleration and turbo spooling. Since turbos have to build up boost pressure and react to increases and decreases in exhaust pressure flow rates, they may not respond as quickly as superchargers, which are fed by power directly from the engine.
How Much Power Does a Supercharger or Turbo Add?
While the power gained by adding a supercharger or turbo are comparable, the power requirements of a supercharger reduce its total added horsepower slightly. For that reason, a turbocharger often adds slightly more power when the vehicle is tested on a dynamometer, between 70 and 150 horsepower, while a supercharger may add between 50 and 100 horsepower. These numbers also depend on what type of engine you have, what type of supercharger or turbo system you choose, and a variety of other factors.
One thing to consider before adding a supercharger or turbo to your vehicle is the amount of boost that the unit produces. Larger turbos and superchargers produce more boost which can translate to more power, but you may not see the expected power gains if your engine is not structurally equipped to handle the amount of extra incoming pressure. Your engine may also be damaged by the excess pressure, and it’s possible for uncontrolled boost pressure to cause gasket failure or even blow out a cylinder wall if the unit is not installed properly. Bigger isn’t always better when it comes to choosing a turbo or supercharger, so be sure to do your research to see what will provide the best results.
To limit the risk of excess boost and engine or damage, a blow-off valve and wastegate are also typically integrated into a turbocharged system. A wastegate bleeds off boost pressure above a set threshold to keep from damaging the turbo or the engine, effectively limiting the amount of boost that can be produced as the turbocharger spools. A blow-off valve works to control boost after combustion, reacting to a decrease in exhaust pressure as the engine speed drops and releasing “leftover” boost pressure. This prevents the turbo from being damaged by returning pressure to optimal levels for the engine’s current fuel and air consumption. If either the wastegate or blow-off valve do not work as they should, extremely high boost pressures could result in damage to the engine or the turbo itself. Replacing a damaged or failing wastegate or blow-off valve should be a priority to prevent more costly repairs or catastrophic engine failure.
How Does a Supercharger or Turbocharger Increase Fuel Mileage?
It may seem counterintuitive that increased performance could also save gas, and in the wrong circumstances, supercharging or turbocharging a vehicle will not increase fuel mileage. Forcing more oxygen-dense air into the engine actually requires more fuel to combust properly, so how does forced air induction increase fuel mileage? The simplest answer is that it doesn’t necessarily, but it allows smaller, more fuel-efficient engines to generate additional power. Many people refer to turbocharging and supercharging as a “replacement for displacement”, meaning that a considerably lighter engine (typically with fewer cylinders) can be made to produce comparable power to the more traditional large-displacement engines while maintaining their fuel efficiency.
Highway driving is where there may be a more notable difference between naturally-aspirated and turbocharged vehicles. While driving in the city, the turbo may be utilized more frequently, and stop-and-go traffic requires the turbo to “spool” more frequently to keep the engine boost levels up and deliver improved acceleration and appropriate power. When driving on the highway, the turbo isn’t required because the vehicle is already in motion consistently, and the benefits of the smaller-displacement engine can really be seen.
Intercoolers
One final consideration in a supercharged or turbocharged induction system is the intercooler. Though not every turbo-equipped vehicle features an intercooler, they are common both in stock and add-on supercharging systems. An intercooler is designed to use air passing through the grille at the front of the vehicle to reduce the temperature of the compressed air before it is delivered to the intake manifold. Compressed air from a turbocharger or supercharger will be considerably warmer than the air coming into the system, and this may not be optimal for combustion. Hot air molecules are also more spaced out, making the air less dense. Intercoolers allow the compressed air to become even more dense, further increasing efficiency due to the concentration of oxygen. Adding an intercooler to your turbo-equipped vehicle, or including an intercooler when adding a turbo or supercharger, may be a great idea to maximize the impact of your repair or upgrade.
Should I Turbo or Supercharge My Vehicle?
There is no right answer to this question. If you’re looking for added performance, it would definitely be a consideration, especially in racing applications. Of course, you can also enjoy the benefits of additional performance on the street, but where induction really shines for typical driving conditions is in delivering a power boost to small-displacement engines and improving overall fuel mileage when city and highway driving are averaged. In either case, installing a turbo or supercharger kit will require considerable modification to your vehicle and is by no means cost-effective or easy to install. In addition to the turbo or supercharger itself, you may also need an aftermarket standalone or piggyback engine control unit (ECU) to properly run a forced induction system on a computerized vehicle. If you have a newer or leased vehicle, always keep the possibility of voiding your warranty in mind. Do some research on your specific vehicle and engine to see if the benefits of adding a turbo or supercharger outweigh the costs, and be certain you know what you’re doing before you start buying or installing parts.
We hope this helped you better understand the benefits of turbos and superchargers, as well as the differences between the two. If this is a modification you would like to perform but you’re not comfortable taking on yourself, you can find a repair shop that specializes in performance upgrades. If you simply need to replace an existing air induction component, O’Reilly Auto Parts also carries replacement turbos and superchargers for production vehicles that were originally equipped with air induction systems, as well as a variety of parts that may be needed to make your repair and restore your car’s performance and efficiency.
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