Typically, even a low-boost small engine turbo can deliver 25% more power than its non-boosted sister.
That means that even a tiny turbocharged i3 can perform just as well as a large i4, or a small supercharged i4 can outperform a V6 or V8.
It may seem obvious that, to improve fuel economy, you reduce the size of the engine, which creates a couple of problems.
While cruising, a small-displacement engine certainly has better fuel economy. The problem lies in accelerating the car to cruising speed. The 1995 Geo Metro, for example, was rated at 49 mpg highway, but getting it on the highway was the difficult part, especially if you trying to merge onto a 65 mph *cough* 75 mph New Jersey Interstate.
The tiny 0.993 ℓ three-cylinder engine generated just 55 hp and, in spite of the car weighing just over 1,800 lb, acceleration just was not this vehicle’s strong suit. For people looking for the best fuel economy in those days, there were very few choices.
Today, people are still looking for fuel economy, but they also want something that won’t get splattered trying to merge on I-287. Those people will be happy to know that turbocharged small-displacement engines are making a comeback, not only because turbochargers are cool and fun, but also because they make better fuel economy.
Today, about 16% of new conventional vehicles are powered by small boosted engines, such as the 46 mpg turbodiesel Chevy Cruze and the 45 mpg Ford Fiesta EcoBoost. These cars get great highway fuel economy, due to their small-displacement engines, but they perform better than their tiny displacements would suggest, which means that fuel misers don’t have to be afraid of the highway. Some studies suggest that, in the next ten years, as much as 90% of cars will feature boosted engines, either turbocharged or supercharged, for better fuel economy and performance. Who knows, maybe saving fuel can be fun, too?