Efficient Three-Cylinder Engines are Coming to America ... Again

As auto manufacturers seek ways to increase fuel efficiency and reduce C02 emissions, they’re looking at smaller engines as one approach. This includes three-cylinder engines in conventional and hybrid electric vehicles. One of the advantages of a hybrid is that a smaller and less thirsty engine can be used without sacrificing performance. The first generation Honda Insight, for example, had a one-liter, three-cylinder engine that helped it achieve its amazing fuel economy that often reached better than 60 mpg. The Chevrolet Volt's range-extender engine will also be a three-cylinder.

Three-cylinder engines have been used in many cars in the past. Saab got its start after World War II with three-cylinder engines and offered them until 1968. Postwar German DKWs were powered with them until the end of the brand in 1965. The East German Wartburg, which was a DKW design, also used three-cylinder engines until 1998. These all were two-stroke engines. DKW even marketed its cars as ‘3=6’ models because the company said these three-bangers offered the performance of a six-cylinder engine.

In more recent years, three-cylinder engines, now four-stroke, were used in the Geo and Chevrolet Metro models that were really Suzuki's rebadged Cultus. This was also sold in the U.S. as the Suzuki Swift. Earlier three-cylinder Daihatsu Charades were sold here as well. The three-cylinder Subaru Justy was the last car sold in the U.S. with a carburetor in 1990. Many Japanese automakers use three-cylinders in their ‘kei class’ micro-cars.

Today, three-cylinder engines are used in several world cars including the smart fortwo that’s sold in the U.S. It’s powered by a 1-liter, three-cylinder engine. A three-cylinder turbodiesel engine is available in other markets. Since 2003, Volkswagen’s Skoda subsidiary in the Czech Republic has offered 1.2 liter gasoline and 1.4 liter diesel three-cylinder engine in its Fabia models. Newly revised Skoda-built, three cylinder engines used in the Fabia will likely be used in the VW Polo, Seat Ibiza, and even a new Audi A1, all of which share the same platform.

PSA Peugeot Citroën plans on introducing a new line of 1-liter, three-cylinder engines in the 70- to 100-horsepower range in order to offer vehicles with CO2 emissions below 100g/km with no exotic technology required. PSA is setting up two manufacturing sites to build the engines. The first one will open in 2011 with an annual build capacity of 600,000 engines.

Use of three-cylinder engines may not be limited to just low budget vehicles. In fact, both Mercedes-Benz and BMW are reportedly developing more pint-sized engines with three cylinders. Mercedes-Benz is looking at their use in its future small cars and hybrids, with A- and B-Class models the most logical applications for these small engines.

BMW is also said to be working on a new range of smaller three- and four-cylinder engines, potentially for the next generation 1-Series cars and possibly in an oft-rumored new Isetta brand. The latter would have two more cylinders than the original. Sources say the 1.3 liter, 3-cylinder powerplants could have outputs ranging from 163 to a turbocharged 241 horsepower. These are pretty impressive numbers since most three-cylinders are in the 1-liter range with under 100 horsepower. Naturally, turbocharging is used in many other three-cylinder engines to boost output.

Three-cylinder engines are another instance where technology, especially electronics and computers, can overcome inherent mechanical challenges such as rough running. Inline-three engines usually use a crank angle of 120-degrees so they are rotationally balanced. However, by design three cylinders are offset from each other so the firing of the end cylinders induces a rocking motion from end to end, since there is no opposing cylinder moving in the opposite direction as in a straight-six. A balance shaft and good engine management technology can be used to create a smoother running engine.