Turbocharger Buying Guide

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Turbocharger Buying Guide

A turbocharger, a form of supercharger, is a gas compressor that is used to force air into an internal combustion engine. It basically increases the density of the air that is entering the engine in order to generate more power. The exhaust gas from the engine drives the turbine, and the turbine powers the compressor of the turbocharger. The performance of a turbocharger is high because it does not use a direct mechanical drive. As compared to a naturally aspirated engine in which only atmospheric pressure is used, a turbocharged engine is more powerful and efficient because the turbine used pumps in more air into the combustion chamber. All forced induction devices were earlier known as superchargers. At that time, a turbocharger was known as a turbosupercharger. These days, the term supercharger is reserved only for mechanically driven (from an engine), forced induction devices.

Basic knowledge of turbochargers and their major components, applications, and features is absolutely necessary for a buyer to make a purchasing decision without professional assistance. Turbochargers are available from automotive stores or from online sites like eBay if a buyer is certain of his or her needs. Automotive repair shops are another buying alternative for buyers who want assistance choosing the correct turbocharger.

Components of a Turbocharger

When the various components of a turbocharger work together, the engine gets an extra boost and the vehicle accelerates accordingly. The major components of a turbocharger consist of the turbine and the compressor.

Turbines

Turbines in turbochargers are mostly radial inflow turbines. The turbine is used to capture the kinetic energy of the exhaust gas and spins at around 250,000 rpm. The turbine housings direct the gas flow through the turbine. The performance of the turbocharger is affected by the shape and size of the turbine. Manufacturers mostly offer a basic turbocharger assembly along with multiple housing choices for the turbine. This allows users to manage the response, performance, and efficiency according to their own preferences. The turbine and impeller wheel sizes control the amount of the exhaust gas and also dictate the relative efficiency of the operation. Generally speaking, the larger the compressor and the turbine wheel, the larger the flow capacity. The different variants include the arching, number of blades on the wheel, measurements, and shape.

The performance of a turbocharger is highly dependent on the size. Small and large turbochargers each have their own pros and cons.

Performance Factor

Large Turbocharger

Small Turbocharger

Heat and Pressure

Takes more heat and pressure to spin the turbine

Takes less heat and pressure to spin the turbine

Turbo Lag

Lags at lower rpms

Virtually non-existent

Spin

Not very quickly

Very quickly

High Acceleration

Better performance

Average performance

In order to enjoy the benefits of both, an effective combination is often used. Some good examples of such combinations include variable-geometry turbochargers, twin-turbochargers, and twin-scroll turbochargers.

Twin-turbo or bi-turbo designs, as the name suggests, have two turbochargers operating either in a parallel or series connection. For parallel connections, each of the two turbochargers is fed one-half of the exhaust gas. In a series connection, one turbocharger operates at lower speeds while the other is turned on at a predetermined load or engine speed. This symmetry helps reduce the turbo lag. A set of pipes, however, is required to properly feed both turbochargers. In engines of more than 2,500 cc and boxer or V-shape engines, there is a trend of using two small turbochargers rather than one large turbocharger because smaller turbochargers, as mentioned in the table above, have less turbo lag than the large turbochargers.

Divided or twin-scroll turbochargers have two nozzles and exhaust gas inlets. One nozzle is for quick response. It is small, sharp, and angled. The other one is for peak performance and is less angled. Nine moveable vanes are used to adjust the airflow to a turbine in a variable-geometry or variable-nozzle turbocharger. The size of this kind of turbocharger is optimised for the entire power curve. The angle of the vanes placed in front of the turbine is adjusted using an actuator to control the airflow to the turbine. This variability results in increased fuel efficiency with a minimal turbo lag.

Compressors

A compressor and a turbine collectively form a turbocharger, wherein the turbine powers the compressor. The compressor increases the density of the intake air that enters the combustion chamber, and this results in a boost for the engine and the generation of more power. A diffuser, impeller, inducer, and volute housing generally form a compressor. A compressor map describes the operating range of a compressor.

The two main types of compressors mostly used in turbochargers are centrifugal and axial flow. Turbocharger size should be small for some applications. In such cases, centrifugal compressors are the preferred option. Internal modifications are often required in some large radial units in certain applications. In these cases, axial flow compressors are mostly employed.

Applications of a Turbocharger

Turbochargers are used in several types of vehicles. With the overall improvements that have been made in turbochargers, they are starting to be used in more and more applications. Some notable applications of turbochargers include use in diesel cars, motorcycles, and aircraft.

Diesel-Powered Cars

Most of the diesel engines of today are turbocharged. Reasons for the high-scale use and increasing popularity of turbocharging include improved driveability, efficiency, and performance of turbocharged diesel engines. Turbocharging immensely enhances the engine's power and power-to-weight ratio. The smart use of turbochargers reduces the turbo lag and allows trucks and industrial diesel engines to operate at their maximum speeds. As there is no engine knock in diesel engines, high boost pressures can be managed easily by diesel engines, unlike gasoline-powered engines. As for trucks, the first turbocharged truck was produced long ago in the year 1938.

Motorcycles

High-performance turbocharged motorcycles were first introduced by some Japanese companies in the early 1980s. Kawasaki Z1R TC was the first turbocharged motorbike produced in the year 1978. Motorbikes were powered up but were only slightly faster than standard motorbikes, and turbo applications increased their cost. Since the boost in performance was not worth the extra cost, manufacturers abandoned their production after the mid-1980s.

Aircraft

According to some sources, one of the reasons for manufacturing turbochargers in the first place was to enable aircraft to fly at higher altitudes. They have since been refined and modified to suit on-ground vehicles and improve their efficiency, as well. The air pressure at high altitudes drops dramatically as an aircraft climbs. The problem is resolved by a turbocharger, which compresses the air to increase the pressure.

Features of a Turbocharger

Turbochargers pump air into the cylinders to increase the density of the intake air. A conventional engine differs from a turbocharged and supercharged engine because it does not force air into the chamber.

Charging Efficiency

The charging efficiency of a turbocharger is its ability to draw the air in. A conventional engine has a charging efficiency of 65 per cent to 85 per cent. The charging efficiency of a turbocharger or a supercharger, however, may be more than 100 per cent, without breaking the laws of thermodynamics.

Compression Ratio

With the increase of compression pressure in a gasoline engine, the chances of an engine knocking greatly increase. In order to prevent knocking, the compression ratio of a turbocharger engine is kept lower than that of a conventional engine.

Turbocharger vs. Supercharger

Turbochargers have a relatively low parasitic loss, and this is a desirable feature. Superchargers derive power from the engine and then generate more power for it. The consumed, non-negligible power, is the parasitic loss, expressed in horsepower (HP). The term supercharger is now applied only to mechanically-driven, force induction devices.

How to Buy a Turbocharger on eBay

The easiest way to find a turbocharger on eBay is to use the search bar on the eBay homepage. Enter a relevant query to begin the hunt. For some entries, eBay may suggest other related searches that could make the searching process even easier at times. Some queries for this type of item might include 'turbocharger', 'supercharger', et cetera. You can then filter the results on the basis of your own preferences.

When you get ready to search for a turbocharger on eBay, be sure to enter your postcode to filter the search results by location in order to save on delivery charges. If you cannot find anything close to you, you can still consider options with shipping. If the item you are looking for is found in your area, arrange a local pickup with the seller, and you can pick the item up when your transaction is complete. Reading user reviews and the seller's feedback comments is also a recommended practice as it gives you a better idea of the integrity of the seller.

Conclusion

A turbocharger forces air into an internal combustion engine to increase the overall power of the engine. The term superchargers is now used for mechanically-driven, force induction devices. A turbocharger is largely a combination of a turbine and a compressor. In order to capitalise on the benefits of both large and small turbochargers, an effective combination is often used instead. Twin-turbochargers, variable-geometry turbochargers, and twin-scroll turbochargers are a few of the common combinations.

The response, performance, and efficiency of a turbocharger can be adjusted according to one's own preferences. Turbochargers are commonly used in aircraft, diesel-powered cars, and a few other types of vehicles. The compression ratio of a turbocharger engine is kept lower than that of a conventional engine in order to avoid engine knocking, and the charging efficiency of a turbocharger can exceed 100 per cent.

A buyer should learn about the applications, features, and components of a turbocharger before attempting to purchase one on his or her own. Mechanics at repair shops may be willing to assist buyers with purchasing. Well-prepared buyers can turn to sources like eBay online or local automotive stores to purchase turbochargers.

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