Hodges 1
Daulton Hodges
English 1010: Composition 1
22 March 2012
Supercharger vs Turbocharger One of the most commonly used ways to give a vehicle more horsepower and torque is by forced induction. There are two different ways to force induct a vehicle. One is a Supercharger, and the other is a Turbocharger. The conflict with this between people is deciding which one is better. Both superchargers and turbochargers have their advantages and disadvantages, some of which are similar. Choosing the right kind of forced induction will depend on your vehicle’s motor, and your power expectations. The first type of forced induction system is a supercharger. There are different types of superchargers. The first type is a root supercharger which is the oldest by far. Root type superchargers push extra oxygen into an engine by using meshed-lobe rotors. The rotors rotate in opposite direction trapping the air into pockets and forcing it from the inlet to the compressor chamber where it is compressed and moved into the engine. Root type chargers are simple and have few parts which results in reliability and require very few repairs. They are also good for adding power to an engine at low rpm’s. The second type of supercharger is the Screw. The screw type supercharger works very similarly to root type chargers. Screw superchargers are very good at moving air and lose very little of it. They can compress air as they move using their screws. The last type of supercharger is a Centrifugal supercharger. They are very similar to many pumps or fans. They pull air through an intake or compressor housing using an impeller which collects the air and forces it out into a progressively smaller
Hodges 2 area, compressing it and leading it to the engine. Centrifugal chargers are excellent at moving large volumes of air. They are amongst the most efficient and effective superchargers. They also have few moving parts which makes them quiet, reliable, and require little maintenance. They also generate less heat then their more complicated equivalents. Of all types of superchargers, they all are effective at delivering boost almost instantaneously due to them being driven by a belt connected to the crank. This instant boost means more power instantly to the engine. Superchargers also have disadvantages. The biggest and main problem with superchargers is that since they are driven by a belt connected to the crank to deliver instant power, they are not as effective as obtaining as much power as a turbocharger, because a supercharger takes power to make power. The belt that drives the supercharger to make power, takes engine power to rotate. A supercharger engine loses approximately 20% of its potential power because it is belt driven. Another problem is that if your supercharger is setup to produce 10psi of boost, it will not make its full 10psi until the motor is revving almost as high as it will rev. Root superchargers are not good at producing high horsepower in high rpm’s which is generally why you find them on engines that operate at lower rpm’s. Screw superchargers are significantly less powerful before reaching high rpm’s. If used on engines that never reach high rpm’s, they never reach their potential. Centrifugal chargers put a limited amount of pressure on air. They also perform less effectively at low rpm’s. The other type of forced induction system is a turbocharger. A turbo operates almost the same way a centrifugal supercharger would, except it is not driven by pulleys and belts connected to the engines crankshaft. Turbochargers are driven by the engines exhaust gasses that have been removed from the engine and driven through a turbo manifold. The turbo manifold is connected to the turbo’s exhaust housing that takes the engine exhaust gasses and spins a turbine that drives the impeller
Hodges 3 in the compressor housing which compresses the air the same way a centrifugal supercharger does, and sends the compressed air through a intercooler , if equipped, to cool down the compressed air and leads it to the engine’s intake. The higher the engine revs, the more exhaust gas is created to drive the turbine. Once the turbo is driving compressed air to the engines intake, that compressed air is now creating more volume of exhaust gasses which in turn means spinning the turbine in the turbo faster and faster. A turbo will create as much boost depending on the size of the turbo, and how much exhaust gas the engine sends through the exhaust housing to spin the turbine or the engine size. A turbo can add mass amounts of power to an engine and require no extra power to make power because it is driven off the exhaust gasses. There are hundreds of different types of turbochargers. The different types are all based on their size of the exhaust and compressor housings, the type of flange they have, and the type of bearings they have. Each and every different turbo is rated on how much air it can deliver to the engine. The bigger the turbine, typically the more air it can deliver at full boost. But the bigger the turbine, the more exhaust can pass through, reducing back pressure. The problems with turbochargers, is that they are very complex. A lot more parts are involved. Turbos create a lot of heat because of the exhaust gasses which means it makes them vulnerable to damage the turbo bearings which will shorten the life of it. The only way to limit the amount of maximum power a turbo will create to provide to the engine, is with a wastegate. There are turbochargers with internal wastegates that are built in the turbo’s exhaust housing, and some with external wastegates that are mounted to the turbo manifold. They both do the same thing which is to release some of the exhaust gasses from an engine into the atmosphere before it reaches the turbine which puts a limit on the amount of exhaust spooling the turbine. The wastegate valve opens and closes with the pressure in the intake. Vacuum pulls it shut and positive pressure or boost opens it to release
Hodges 4 the exhaust gasses. Sometimes, the wastegate valve will stick and not open to release exhaust which sends all the exhaust to the turbine and can dangerously over boost an engine’s ability to withstand it and destroy and engine internally. A blow off valve or BOV is connected to the charge pipe that contains the compressed air going to the engine. A BOV is not just made to make a cool “pshhhh” sound, it si made to protect the turbo from damage. When a turbo is sending the compressed air to the engine, and the throttle body on the intake shuts from letting off the gas pedal when driving, all the compressed air is trapped in the charge pipe and the easiest way out if back through the turbo’s intake system. If this happens and the turbo is under full or high boost, it can damage the turbine, turbo seals, bearings, and the compressor impeller, altogether, destroying a turbocharger. The BOV is placed on the charge pipe near the throttle body and will remain shut until the throttle body closes. Once it closes, the excess pressure in the charge pipe is released through the BOV, making the cool “pshhhh” sound and protects the turbo. The other biggest main problem with a turbocharger is a good/bad thing. Although turbos can create huge amounts of extra power for an engine, they have what is called “spool time” or “lag”. The bigger the turbo, the more power it is capable of making, but in return, the bigger is it, the longer it takes to spin up to create boost. This is called lag. The turbo must actually spool up before it will compress any air because it is driven by exhaust gasses. Lag is the time it takes for the turbine to reach its full throttle from an average rotational speed state. During this time, little or no boost is created which means no power gains for a faster acceleration. The smaller the turbo, the less lag is created for a faster acceleration, but the less maximum power is generated. Depending on your engine size will depend on the proper size turbo application for an engine. The differences between superchargers and turbochargers are endless and each person will have his or her opinion on which is better based on their engine. It is defiantly certain that the
Hodges 5 turbocharger will produce more power and is more efficient which is the purpose of forced induction, but on the other hand, a supercharger produces no lag and a lot less complex. Everyone has their own preferences so there is no winner in which is better. Choosing which one to run depends completely on the type of setup you want and how you want to run it, your power goals, and they type of engine you have.