The benefits of gasoline engine downsizing has its latest poster child: the new Polo GTI. It’s a graphic example of why diesel market share in Europe is declining, especially in smaller cars: a 25% reduction on the European mileage standards, without any loss of performance. The GTI’s 1.4 liter TSI produces 177 hp (132kW), exactly the same as its 1.8 liter predecessor. But the combined fuel consumption is 5.9 L/100km (40 mpg US)—equivalent to CO2 emissions of 139 g/km, 25% lower than the outgoing model. Knowing that it also squirts to 100km (62 mph) in 6.9 seconds and comes standard with a 7 speed DSG transmission is only rubbing the wound of knowing it’s not coming to the US with salt. But undoubtedly, tightening CAFE standards will eventually send VW’s pioneering 1.4 and 1.6 TSI engines our way; the question is only in what body.
VW’s small TSI engines are to gas engines what it’s also pioneering TDI engines were to the diesel world: a breakthrough in shattering assumptions of what small artificially-aspirated gas engines are capable of, in terms of both performance and economy. Due to its combination of supercharging and turbocharging, an semblance of turbo lag is history. The 177 hp Euro-5 16-valve four-cylinder engine reaches its maximum power at a relatively low (for such a small engine) 6,200 rpm. Maximum torque of 250 N·m (184 lb-ft) arrives at 2,000 rpm and stays at a constantly high level up to 4,500 rpm. The effect is to recreate the feel of a much larger normally aspirated engine without any of the typical detriments.
Another graphic example of the narrowing gap of diesel and gas consumption is in the European Golf: two almost identically powered Golf VI versions: 140hp TDI – 5.4L/100km (43.56mpg); 160hp TSI – 6.0L/100km (39.2mpg). That represents a 10% difference. Meanwhile, the US version gas Golf slogs along with its antiquated 2.5 liter five that bumbles through the EPA test with a 26 combined rating.