What are the differences between TSI, TDI and DSG Cars?

Published: 13th June 2011
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Many cars on the road these days are marketed as coming with TSI, TDI, or DSG features. However, for people who are unfamiliar with these terms, the process of choosing a car to drive can seem rather daunting. This article will describe the differences between cars marketed as TSI, TDI, and DSG.

First, TDI is shorthand for turbocharged direct injection; this is a way turbo diesel engines may be designed. The design includes both cylinder direct fuel injection and turbo charging. Direct injection refers to the process in an engine through which fuel is sprayed from a fuel injector into the combustion chambers of each cylinder in an engine. The fuel is atomized, and the process here may be contrasted with that in an older diesel engine, where indirect injection is used. Forced induction through a turbocharger can also be used by the engine so more air is then able to find its way to the cylinders of the engine.

Intercoolers are also frequently used in these engines to increase the density of compressed air that enters from the turbo; this is done by lowering the air temperature. As a result of the compressed air and the increases in fuel injection and combustion, greater engine efficiency and power outputs are possible in comparison to petrol engine counterparts. Similarly, emissions are decreased and torque is increased in comparison to petrol engines that are not turbo charged or directly injected.

Second, TSI is shorthand for petrol engines that feature both twin charger and fuel stratified injection technology. The twin charger is composed of both a turbo charger and a super charger. The term TSI may also be used to describe engines that include fuel stratified injection and a turbocharger but not a supercharger; however, the more common use involves the combination of fuel stratified injection and the twin charger.

As you can see, differences between TDI engines and TSI engines start with the fact that TDI engines are powered by diesel while TSI engines are powered by petrol. Since petrol usually costs less than diesel per gallon, it will cost less to fill up a vehicle that uses a TSI engine than one that uses a TDI engine, presuming the same amount of fuel is added to both.

However, because diesel fuel carries more energy than petrol fuel and diesel engines are more efficient than petrol engines, in the long run, it will take less fuel to propel a TDI engine a particular distance than a similar sized TSI engine. Similarities between both engines include the fact that both make use of turbo chargers. Both also make use of direct injection of fuel, although it is known as direct cylinder injection in TDI engines and as fuel direct injection or fuel stratified injection.

Third, DSG is shorthand for the direct shift gearbox. The direct shift gearbox is a dual clutch multiple shaft manual gearbox that is controlled by the computer within the car's engine; the design involves a transaxle but does not involve a conventional clutch pedal. As a result, full automatic and semi manual controls are included. To put things another way, a DSG essentially involves two independent manual gearboxes and clutches that are housed in a single housing and chained to work together as a single unit.

The design of two independent clutches allows for faster shifting times while eliminating the need for a torque converter that is present in a conventional automatic transmission design. The DSG differs from TDI and TSI in that it is a transmission design rather than an engine design, and it may be used in both TSI and TDI cars.

Hugh McInnes is a freelance writer with a passion for cars, new cars, vintage cars, 4WDs, you name it. He also has a severe case of the travel bug, recently he took off to Europe, found a cheap european car to rent and hit the open road to see the sites.

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