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Volkswagen is replacing the naturally aspirated 1.6 and 2-litre petrol engines in its Golf hatchback line-up in New Zealand with a smaller capacity 1.4-litre unit equipped with the carmaker's revolutionary twin-charger technology.
The 2-litre has already been dropped and the 1.6-litre will be gone by the middle of
the year.
VW general manager Dean Sheed says twin-charger stratified injection (TSI) makes the 1.4-litre engine more energy efficient than bigger naturally aspirated four-cylinder units such as the 2-litre.
"TSI is the future of smaller capacity petrol engines as far as VW is concerned," Sheed says. "It provides a solution to what is worrying the world - the use of fossil fuels and global warming from carbon emissions.
"The 1.4-litre engine has more power, better fuel economy and cleaner exhaust emissions than the 2-litre. It's what our customers want."
The TSI engine made its first appearance in New Zealand late last year under the bonnet of the $47,990 Golf GT, an addition to the hatchback range. At the international engine awards in Germany in September it was named the year's best.
Industry analysts say TSI is groundbreaking technology. Mercedes-Benz is talking to VW about TSI and BMW is looking at similar technology.
VW says its aim was to build a small-capacity petrol engine that provided performance and driveability that was about equivalent to the output of the carmaker's discontinued V5 2.3-litre, but with improved fuel consumption and lower emissions.
Using a turbocharger alone to get more air into the engine didn't produce what VW wanted. A turbocharger runs off the engine's exhaust gases. The upside is that it doesn't sap engine power.
The downside is the delay before exhaust gas pressure gets high enough to work the turbo to force more air into the mix. This is known as turbo lag.
A supercharger runs directly on engine power and works instantly. But the higher the revs the more power it draws from the engine. Result: it isn't as efficient at the top end.
VW says it combined the advantages of turbocharger and supercharger but left the disadvantages behind.
TSI uses a supercharger for low revs and a turbocharger for high revs. VW says that despite the 1.4-litre capacity the combination of supercharger and turbocharger enables the TSI engine to produce 125kW (170bhp) of power at about 6500rpm, and 240Nm of torque between 1500 and 4750rpm, a similar output to the V5.
It's this flat line of torque - at 1000rpm the engine is producing 175Nm - that contributes to improved driveability.
Between engine speeds of 2400 and 3500rpm, both the supercharger and turbocharger contribute to boost pressure.
At 3500 rpm the supercharger is deactivated through a magnetic clutch, leaving just the turbocharger in operation. VW says the transition between the boosters is seamless.
TSI also improves fuel consumption at speed. At a constant 180km/h on a German autobahn up to 40 per cent of fuel use in a standard car goes towards cooling its exhaust system.
The TSI engine, says VW, doesn't use any additional fuel for cooling the exhaust until speeds exceed 210km/h. That was one of the engineering goals for the direct-injection 1.4 unit.
TSI also provides relatively low consumption, says VW. The Golf GT delivers 7.2 litres/100km, about 40mpg.
Exhaust emissions are cleaner too, it says, at 169g of CO2 a kilometre compared with 211g from the 2.3-litre engine.