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What is TSI's meaning for cars?

If you are considering buying a TSI (meaning a car with the letters TSi following its model name), then it may not have even occurred to you what these three letters actually mean. The fact is, many carmakers use quite complex terminology whether they are addressing something to do with the engine, the chassis design or the interior specifications and trim levels of their products these days.

As such, you might not even think twice about a few seemingly random letters following the make and model of your intended purchase. This would be a mistake with TSI, however, since cars that are TSIs have some specific qualities that it is worth knowing about.

Read on to find out more about TSI's meaning.

To begin with, TSI stands for turbocharged stratified injected, a term that relates to the type of engine the car in question has been fitted with.

You will see both TSI – all capitals – and TSi both in use. However, these mean the same thing and are just different ways that the term turbocharged stratified injected is shortened depending on the context you read it in. In other words, TSI's meaning doesn't change just because you see a lower case I at the end of the abbreviated form. An engine that is a TSI will have been designed to be more lightweight than other versions of the same capacity, often with a higher power and more fuel-efficient construction than a four-cylinder traditional combustion engine could offer.

As a driver, one of the things you should know about owning a car with a TSI engine is that it will often offer more low-end torque and power than you'd get with a standard turbocharged engine. Many car designers and motoring journalists have noted that such four-cylinder engine designs have historically struggled with lower-end torque. By utilising a greater level of pressurised fuel injection and a smaller displacement volume, TSI engines can often perform better than larger engines. In turn, this means drivers can get more power for a more fuel-efficient car. What's more, they come with a high-tech inter-cooling system and some other elements of intricate engineering to offer good long-term performance. If you are a motorist who wants more out of their engine but doesn't want something that will guzzle fuel at an alarming rate, then seeking out a TSI car may well be among the best options.

Which car manufacturers use the term TSI?

Only one car manufacturing group has TSI technology today. To be clear, other carmakers have similar systems that are designed to do the same or a similar job as TSIs. However, it is only Volkswagen Group that uses the specific term TSI for a turbocharged stratified injected engine.

As such, the VW Passat, Tiguan and Atlas are all models that can be found bearing the TSI badge. Many editions of the Golf can also be found with the letters TSI following its name. Even some smaller cars made by VW, such as the Polo, for example, come with TSI variants.

Of course, Volkswagen Group does not just comprise VW vehicles nowadays. As such, you will also find many Seat cars on the road bearing the TSI emblem, too. Aronas, Leons, Tarracos and Ibizas can all be TSIs, for instance. The same goes for Skoda. This car brand has been part of the VW Group for some time and various models it has made historically – as well as today – bear the all-important three letters TSI. Some of the Skoda models that have been made with TSI engines include the Kamiq, the Superb, the Scala and the Fabia. Many Octavias and Kodiaqs in Ireland will also be TSI variants.

When it comes to Audi – also a part of the wider Volkswagen Group – the term TSI is also used. However, in the main, Audis with turbocharged stratified injected engines are not called TSIs. Confusingly, they are more often called TFSIs instead. The reason is that Audi production lines produce turbocharged fuel stratified injection engines. The extent to which this technology actually differs from standard VW TSI engines is open for debate. In many people's eyes, the two terms are nothing more than a bit of marketing with few, if any, tangible differences.

It is also worth noting that VW Group owns Lamborghini, Bentley, Porsche and Ducati. The carmaker does not use the term TSI for any of the engines that are developed for those marques. However, Porsche does use TSI for another reason. In this sense, TSI stands for technical services information, something that has nothing whatsoever to do with turbocharged stratified injected engines. This can sometimes cause confusion, so it is worth knowing that the two brands use the term in very distinct ways from one another despite being part of the same group.

Does TSI's meaning differ from TDI?

Yes, it does. TSI relates to petrol-powered engines only. Perhaps confusingly, VW developed its TSI engine from much of the know-how it had developed from producing more powerful but less fuel-hungry diesel engines. Although both engine types are very different, the German carmaker was able to transfer some of the same design principles from its diesel turbocharged engines into turbocharged stratified injected petrol engines. By contrast, VW's term for diesel engines is turbocharged direct injection (or TDI). As such, both TSI's meaning and that of TDI are extremely close to one another.

Moreover, neither abbreviation refers to the fuel type that the engine is running on. Incidentally, that's one reason that Audi petrol cars with this sort of engine technology use TFSI as an alternative. However, the important thing to take on board is that TSI refers to stratified injected petrol engines, whereas TDI refers to direct injection diesel engines. Both are turbocharged versions. For many, the D in TDI makes it easy to remember that these engines are for diesel cars while TSI (by simply using a different set of letters) must be for petrol-powered ones instead. That might not be the way VW envisioned the use of their engine shorthand when the technology was first launched, but it remains a useful way of distinguishing the two terms from one another.

How does a TSI engine work?

To begin with, the driving principle behind Volkswagen's TSI engine design is the system that allows for direct fuel injection. Like other manufacturers' direct fuel injection engines, TSI systems work by sucking a mixture of liquid and air into a cylinder. After this, the mixture is compressed by a piston and then it is ignited with a spark. As the corresponding piston is forced outwards, it produces power. Traditional fuel injection engines have their petrol and aid pre-mixed in a separate chamber called an intake manifold prior to them entering the cylinder. With a TSI engine, however, air and petrol are not pre-mixed. Instead, only air will enter through the intake manifold, but the petrol will be injected directly into the cylinder. This is the same with all direct injection engine technology, of course.

What Volkswagen has successfully done is to combine the latest injector technology developed from its TDI system to shoot petrol directly into each of the engine's combustion chambers at even greater pressure than was possible before. As a result, fewer energy losses occur from pumping fuel which leads to a more efficiently running engine. Therefore, generally speaking, TSIs need less fuel for the power they produce and, as a consequence, emit less pollutants than other engine types.

Even more crucially, perhaps, a TSI engine will combine direct injection with turbocharging, the mechanical process by which more air flowing into the engine's cylinder can be compressed thanks to the use of exhaust gases. In some cases, so-called twin-charging – whereby compound forces are captured and effectively reused in the engine – is also used in TSI engines, notably many of the 1.4-litre versions VW has thus far produced. Such engines are equipped with both a turbocharger plus a supercharger, and they work together in various combinations. Typically, a TSI supercharger would operate at lower revs, while a turbocharger would kick in as the engine's speed picks up.

Finally, it is worth adding that one other important aspect of a TSI engine's design function is its intercooler. This has the purpose of reducing the temperature of the air entering any TSI engine from wherever it has been sourced. Simply put, when air intake is cooler, it allows for more of it to come in. The intercooler consequently lessens the possibility of back-firing or engine knocking. Although the cooling system may not be the most widely understood part of a TSI engine design, it is essential for it to continue to operate in the high-performance and fuel-efficient manner that motorists have become accustomed to in recent years.


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