The Volkswagen Polo TSI engine tech explained

Volkswagen is set to launch its most energetic Polo version yet in India, the Polo GT. But, what makes it special? Three words â€" Turbo Stratified Injection or TSI. It's not a new technology, and we have seen it on the Jetta before in India, but among small cars, it certainly is a first. Here's what these three words really mean…

TSI is the VW group's moniker for their forced induction, direct injected petrol engines. VW group came up with this technology when the need arose for smaller displacement engines as a way to cut emissions. But, these replacement engines had to make roughly the same power and torque as the larger displacement ones.

Internationally, the VW group offers two kinds of engines under their TSI brand. One is a turbocharged petrol engine with direct injection while the other gets a mechanical supercharger in addition to the turbocharger. The benefit that the twin-charged engines have over the turbo engines is that the power delivery is much more linear and has no unpleasant bumps or peaks in the middle of the rev band.

In India, we get only the turbocharged version of the TSI engines. The first car to feature this engine was the Skoda Laura with its 1.8TSI engine. This same engine later made its way into the Superb as well. But when it came to the VW brand, the only car that got the TSI engine was the Jetta. That too, the 1.4 and not the 1.8 like we had hoped.

So how is the TSI better than the naturally aspirated engines?

There are two bits to this story. First, is the turbocharger. Like I said, the turbocharger lets you make more power from a small engine. And it manages this by increasing the density of air being pumped into the cylinder because of which the percentage of oxygen available for combustion is much higher. As opposed to a bigger six cylinder engine, a turbo-four-cylinder will have lesser moving parts as well which directly translate to lesser friction. Also, there is the obvious benefit of the smaller engine being lighter and hence the engine has less mass to lug around.

The second factor is the direct injection. In a direct injection engine, the fuel is injected into the combustion chamber directly unlike earlier multi-point injection engines which sprayed the fuel into a pre-combustion chamber. This means there's better metering of fuel and because the fuel pressure can be kept high, there's better atomization as well. As a result it gives more control over the fuel air mixture and enables the engine to have leaner mixtures which in turn gives more economy.

Here is our first drive of the Polo GT TSI