Here's What TSI Means (And Why Volkswagen Uses This Engine Tech)

Automotive engines have dramatically evolved over the last century, incorporating advanced technology that allows automakers to essentially make more horses using less fuel. Take, for example, one of the worst V8 engines ever made, the Oldsmobile 5.7-liter diesel V8. The engine was large and likely very heavy, but worse still, it could only output a measly 120 horsepower and got around 18 miles per gallon city.

Contrast those figures with a modern vehicle and you'd be shocked how far performance and efficiency have evolved. We learned first-hand with our 2025 Volkswagen Taos first drive, where the 1.5-liter turbocharged 4-cylinder under the hood now outputs 175 horsepower (although, admittedly, we'd like to see a bit more). With four fewer cylinders and a fraction of the footprint, the Taos engine not only makes an additional 55 horsepower over the Old's V8, but it achieves an EPA fuel economy figure of 28 miles per gallon city.

How is this possible? Technologies like TSI (Turbocharged Stratified Injection) allow smaller engines to not only offer compelling performance but also reduce inefficiencies during operation. TSI is the result of combining direct injection, turbocharging, and an intercooler for highly optimized energy generation. According to Volkswagen, the principle of doing more with less is not only the basis for its TSI engine design, but it has been a company philosophy that began with the iconic Beetle.

One of the methods automakers have discovered for squeezing both more power and miles per gallon out of an engine is a direct injection system. The basic concept of a gasoline direct injection (GDI) engine involves fuel spraying directly into the cylinder. Before direct injection, the fuel and air mixed prior to entering the cylinder, which resulted in some of the fuel getting lost along the way. When sprayed directly into the cylinder (especially at higher pressure rates), precise amounts of fuel are utilized during combustion, thereby creating ample power with less going to waste.

Turbocharging transforms engine performance by forcing compressed air through the engine, enhancing output. While the technology has been around for more than a century, with the first patent in 1905 by Dr Alfred Büchi, it has dramatically improved since. Crucially, due to the increase of additional oxygen with compressed air from the turbocharger, combustion is even more productive, meaning engines aren't required to be large to offer potency under the hood.

Excess heat is always an issue with forced induction and can prevent an engine from reaching its potential. So, what if there was a component that could reduce the temperature of the compressed air from the turbocharger, making it more dense and delivering greater amounts of oxygen and efficiency? Fortunately, an intercooler performs that exact function, helping to keep engine heat down to preserve optimum output.

While there are few sounds as pleasing as a classic muscle car with a big-block V8 rumbling to life, since the 1970 Clean Air Act, ever-tightening emission standards have forced automakers to prioritize cleaner running engines or risk incurring weighty fines. This doesn't mean automakers haven't tried to fudge the numbers occasionally, as Volkswagen's infamous dieselgate scandal demonstrates.

With manufacturers like Volkswagen opting for more compact engines like its turbocharged TSI variants, its vehicles release less carbon dioxide, hydrocarbon and nitrogen oxide, the prime components of unhealthy air pollution. In addition to running cleaner than the larger engines from yesteryear, the TSI also allows Volkswagen to downsize. 

Simple physics dictates that a smaller engine reduces overall weight, so it won't require as much energy to propel vehicle movement. With less energy demand, not as much fuel is needed, making travel more efficient in general. For drivers, a cleaner running engine also helps during regular inspections, though you still might have to contend with some reasons your car didn't pass a smog test and how much it might cost to fix.