With the latest changes in the US fuel economy mandate, manufactures are turning to old tricks to make big power. The old trick is the Turbo Charger. How does this help you say? More power usually means lower MPG. Manufactures like BMW, Ford, VW and GM have all turned to Turbo Charged small displacement engines to try and meet the fuel economy standards. The Turbo charger is basically power on demand. What this means is that a small displacement engine will act like a small engine achieving a high MPG until you need the power. When you coax the power with your right foot the turbo forces air into the cylinders. The air from the turbo is compressed making it much denser than the air outside. This makes the engine larger in a way because the about of air that it is using is equivalent to a larger engines air intake.
The Turbo systems on today’s cars are also much smaller than the old turbo which allows them to spin or spool much faster. The faster spooling allows the engine to get into a meaty torque curve somewhere between idle and 1500 RPM. Torque is what you feel when you step on the gas and get pushed back in your seat. This gets the car or truck moving. In the 80′s turbo chargers became popular but you always had to wait for the power. This has been fixed with smaller turbo chargers and also variable vein turbo chargers.
The other secret in this latest small displacement engine war is Direct Injection. This allows a more efficient use of fuel and a cooling charge for the air that is forced in by the Turbo. With direct injection the engine manufacture can raise the compression ratio of the engine for more power and efficiency. The Direct Injectors are placed right down in the combustion chamber so the fuel does not pass through the intake valves.
I hope this was helpful information and here are some links to wiki articles on my favorite turbo engines.
Ford Ecoboost http://en.wikipedia.org/wiki/Ford_EcoBoost_engine