Volkswagen's New Engine Packs A Variable Geometry Turbo
29 Avril 2016 - Autoblog
Forget the dirty diesels for a moment. Volkswagen is showing its cleaner side at the International Vienna Motor Symposium by introducing the more efficient EA211 TSI Evo engine.
The 1.5-liter powerplant will be the first mass-market gasoline-fueled mill to use variable turbine geometry (VTG) for its turbo. Versions with 129 horsepower and 148 horsepower will arrive in European vehicles by the end of the year. There's no word yet on whether the engine will make it to the US.
VTG allows the turbine's blades to continually adjust, creating a broader torque curve than usually possible from a single turbo. The tech isn't uncommon in diesel engines, but the expense of exotic materials to deal with the higher temperatures in gasoline-fed mills keeps the system limited to the top of the market, at least until now. For example, Porsche already uses VTG on the 911 Turbo and the four-cylinder in the new Cayman and Boxster. The EA211 TSI Evo makes the technology accessible in more affordable vehicles.
To get the most of the system, the EA211 TSI Evo uses the more efficient Miller combustion cycle and runs at a high 12.5:1 compression ratio. The result of these systems working in unison is that max torque is available from just 1,300 revs. VW doesn't specify exact fuel economy, but says it's a 10-percent improvement over the earlier 1.4-liter TSI with 123 horsepower. The mileage gains also come from cylinder deactivation, which shuts off half the engine at appropriate times.
VW Group made a similar switch to the Miller cycle for the 2.0-liter turbocharged engine in the 2017 Audi A4. Unveiled at last year's International Vienna Motor Symposium, the upgraded mill had a wide torque spread and increased efficiency but without the extra benefit of VTG. We hope VW also incorporates the variable turbines into performance models because it could make the GTI an even hotter hatch.