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Green Wheels: BMW 3-cylinder shows smaller is better

Big engines, such as V8, on the wane

Published March 28, 2013

WOODCLIFF LAKE, N.J. — Time was when, in the world of car engines, bigger was always better.

Improvement meant more cylinders, displacement, horsepower and torque.

Those days are long past. True, carmakers still produce fuel-suckers with more power than they, or their drivers, know what to do with. But rising gasoline prices and, more important, increasingly stringent fuel-economy and emission standards, are inspiring a downward spiral.

The V8 is dying, while fours and sixes are shrinking, with direct injection, turbocharging and other engineering tricks making them punch above their dwindling weight.

Now, three is starting to look like a magic number.

Three-cylinder engines made an appearance a couple of decades ago but they were — and I’m being as kind as possible here — underpowered and rough.

They’re back, and a different breed.

Last year, Ford created a bit of a splash with its three-cylinder, one-litre Fiesta — a sprightly little fuel-sipper.

Now, BMW is about year away from commercial production of its own version.

Its three is just the first in a family of “Efficient Dynamics” engines that will include four- and six-cylinder versions — both gasoline and diesel — all based on the same technology and sharing many components. The aim is to rationalize BMW’s current confusing and expensive array of engines and enable it to meet any environmental standard anywhere in the world until at least 2025.

The company brought a prototype three-cylinder to its New Jersey campus to introduce the concept to what it clearly expects will be a tough North American audience. It was installed in the smallest BMW-badged vehicle, a 1 Series hatchback.

The brief test drive and workshops were held in conjunction with the annual New York Auto Show, an event in which, notwithstanding the unveiling of the 2013 World Green Car — the Tesla Model S — vehicles with environmental credentials seemed to be an afterthought.

BMW’s three-cylinder engine, while not presented at the show, was the most interesting development on that score.

Each cylinder displaces 0.5 litres, which the company’s engineers deemed the “sweet spot” for smoothness, performance and fuel economy in all members of the new family.

The engine features direct fuel injection, with carefully tweaked spray intervals and redesigned combustion chamber to produce the most effective burn. Those details, BMW says, are proprietary.

The Valvtronic system electronically controls the intake valves, cutting the amount of air-fuel mixture entering the combustion chamber when the engine is under a light load. It’s a complex system, but BMW says it produces better fuel efficiency and performance than the current main alternative — shutting off half the cylinders.

The system also includes a turbocharger — a single scroll on the three-cylinder engine and twin on the four and six.

Fuel consumption numbers aren’t yet available, but the three-cylinder is said to be five to 15 per cent better than the four.

The three’s output is variable. The prototype generates 177 horsepower and 200 foot-pounds of torque. But the engine is to be used first in the i8 plug-in hybrid sports car, where a bigger turbocharger — made possible because the electric motor will provide low-speed torque — will boost it to 220 horsepower.

After that, BMW will decide where it makes sense to install the smaller engine in place of the current four-cylinder. The 1 Series is the most likely candidate, but it could also make its way into some 3 Series models and perhaps into Minis.

The test drive involved just two laps around the small private roads on BMW’s property. But this limited drive offered hints the new engine will perform very well in a small car; smooth, decent acceleration and speed, and a nice engine note.

BMW says it’s “relentlessly” pursuing electrification of its products, but internal combustion will continue to dominate for the medium term so it’s pushing hard on fuel efficiency.

The new engine is an intriguing step in that direction.

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