Until recently, drivers had to choose between performance and fuel economy when buying a new car. One always seemed to come at the expense of the other, so compromise was usually called for when car shopping. Later, explanations of “I know it’s slow, but it gets good fuel mileage,” or “I know it drinks gas, but it puts a smile on my face” would be handed out to friends and neighbors.
Audi’s looking to change that perception, and its latest engine demonstrates that performance and fuel economy can indeed co-habitate. Called the 1.8 TFSI, the new 1.8-liter four-cylinder produces 170 horsepower and 236 foot-pounds of torque, which is more than enough to provide reasonable acceleration for Audi’s A5 coupe.
That’s a respectable output from a 1.8-liter engine, even a turbocharged one, but its fuel economy is even more impressive. In the Audi A5, the new engine returns an average fuel economy of over 41 miles per gallon, representing an improvement of 21 percent over the A5’s previous 1.8-liter engine. The new engine produces just 216 grams per mile of carbon dioxide, too.
To achieve this, the new TFSI uses both direct fuel injection and indirect fuel injection, which introduces atomized fuel upstream of the combustion chamber, where it mixes with incoming air. Under partial engine loads, this setup reduces both fuel consumption and particulate emissions so much that the engine meets Euro 6 emission standards, not due for implementation until 2015.
Perhaps the most innovative system in the new 1.8 TFSI engine is its electronic coolant regulation system, designed to bring engine oil up to operating temperature as soon as possible following a cold start. This is done by keeping the coolant within the engine block for considerably longer than usual, ensuring that the oil quickly reaches proper temperature. Cabin comfort is controlled via a second coolant line, which circulates through the cylinder heads only. Both systems are controlled via an electronic water pump, and a single radiator cools the separate systems.
The weight of the new engine has been reduced by some eight pounds as well, thanks to the use of a new turbocharger and cylinder head module, a thinner-walled crankcase, fewer crankshaft counterweights and a polymer oil pan.