Dubbed the 2.5FT, the engine is available with both manual or automatic transmissions - new to the flex-fuel V70 and S80. Fuel consumption with the manual gearbox works out to an EU combined cycle rating of 9.2L/100km and 10.2L/100km for the automatic, when running on petrol.
Efficiency on E85 is 30-40% lower, thanks to the lower energy content of ethanol, but the carbon emissions are largely from carbon captured just months before, by the plants or other materials used to make the ethanol.
The previous flex-fuel engine was available only as a 2.0L four-cylinder that generated 145hp (107kW). The new engine is a 2.5L unit that cranks out 200hp (149kW). Volvo says that this is enough power to meet the entire range of daily driving needs in the larger V70 and S80 without the need to richen the air-fuel ratio beyond the ideal point of 14.7:1.
A richer air-fuel ratio occurs when an engine is forced to accelerate very hard, as when using a small four-cylinder to merge with high-speed traffic. The richer ratio allows slightly higher peak power, but worse fuel economy than the ideal air-fuel ratio.
A leaner ratio can result in slightly better fuel mileage, but will result in much higher NOx emissions.
Car makers focus on reaching the 14.7:1 air-fuel ratio (also known as the 'stoichometric' ratio, due to its chemistry-derived origin) in order to maximize the life and efficiency of the catalytic converter. The chemical processes that take place in the catalytic converter produce the best results - in terms of reducing emissions - when the air-fuel ratio in the engine is at exactly 14.7:1.
