Driving BMW's three-cylinder prototype

One of the motoren in the titular Bayerische Motoren Werkeis about to get smaller.

How small, you ask?

The three-cylinder in the cherry-red hatchback shown above is in fact one of BMW's legendary inline-sixes, albeit chopped in half with the proverbial Sawzall. Those sixes have a turbo in the 335i and displace a total of three liters. The three? It has a turbo and displaces a total of 1.5 liters, fitting neatly within the BMW family. Funny how that works out.

At first it may seem a bit daunting to realize that the fine Bavarian product for which you will someday pay through the nose shares the same cylinder count as a 1996 Geo Metro. But this is simply the end result of BMW's continuous quest to meet ever-changing emissions regulations. Europe is heading toward an average fleet goal of 98 grams of carbon dioxide per kilometer, a target that has sent German carmakers protesting. BMW claims that this engine will reduce CO2 emissions across its European lineup by 5 to 15 percent. European manufacturers focus on CO2 over mpg.

The new fleet goal, set to go into effect in 2020, covers the entire BMW Group.This includes the 75-hp Mini First, a model so impoverished it isn't even offered in America. This also includes the V12-engined, 624-hp Rolls-Royce Wraith, recently unveiled in Geneva -- Rolls-Royce, bowing to convention, has finally resorted to the uncouth frippery of publishing power figures. And in between those bookends: legions of the 320i, the ActiveHybrid 5, and California-plated 760Lis with TwinPower engines and -- presumably -- EfficientDynamics stickers on the quarter windows.

The red car above is merely a temporary showcase for the engine, like steak tartare perched on a saltine. BMW paid 20,000 euro per car to bring the hand-built, European-specification 1-series development mules to America, where they come equipped with fire extinguishers and kill switches. Its engineers are halfway finished with development, they said, and they have a little over a year to go. We drove it briefly around BMW's sprawling, cloudy Northern New Jersey campus, because the car is not legally allowed on public roads. They'll be flown immediately back to Europe now that we've gotten our grubby hands on them.

Developmental mule faults aside, the three-cylinder drove remarkably well, reflecting a sound and smoothness that, in our non-scientific minds, felt ready to go. A slight bit of turbo lag rolled into gentle, steady power up until 5,000 rpm, which we were asked politely to not surpass. A quick paddle flick from the eight-speed automatic, and we experienced the throaty, slightly raspy note anew. At no time did we feel that the engine was inadequate for its wrapper, nor did we think that it would shake itself to bits, both problems that the aforementioned Geo Metro might have faced.

The looming European standards have forced BMW to rethink its entire product strategy and even its core philosophy. Hybrids are already appearing in the lineup at a time when BMW seemed, like many Germans, to push diesels. A front-drive BMW could very well happen, using a platform with increased efficiency and easier packaging than a 3-series. Weirder things -- the X6, the GranTurismo series -- have happened, things that threaten to erode the brand's slogan of the "Ultimate Driving Machine." But the fundamental question, the underlying justification for this tectonic shift in BMW's strategy, remains: Why three cylinders? Why not a four-cylinder from a Mini? How smooth can a three-cylinder really be? Why not cylinder deactivation? And why such a small displacement?

BMW answered our questions one by one, with plenty of helpful charts. The displacement is 500c per cylinder because at that size, and with multiples of three, it's the most thermally efficient and least prone to vibration. V8 and V12 engines use a similar-sized cylinder. BMW countered vibration with a hefty balance shaft, to compensate not only for the piston and crankshaft movement but also the short length of said crankshaft. Cylinder deactivation is redundant and uncharacteristic with Valvetronic, which adjusts the valve lift instead of shutting the cylinder down completely -- the difference between an on-off versus a dimmer switch. "The sound of a three is like a six if you tune it the right way," said an engineer. "The responsiveness is huge." After a drive in the prototype, and despite the turbocharger tuning, we would have to agree.

Lastly, BMW wanted to be absolutely clear that a four-cylinder is fine and dandy, but to preserve the sonorous six-cylinder character, one must cut the larger engine in half. "It's not four minus one," BMW would have you think, "it's six minus three."

BMW
The gasoline engine will be the B38, while the diesel will be the B37.

BMW expects thorough flexibility throughout its engine program. Because they share the same fundamental architecture, its four-, six- and three-cylinders can all be built on the same line. The three-cylinder is available in gasoline or diesel with just a handful of unique parts, positioned longitudinally or transversely, on models from the 1 to the 5, driving the rear and even the front wheels, just in time for that purist-grating FWD crossover the company has been threatening to build for years. "It's positioned to react on a volatile market," said a BMW spokesperson. Could this flexibility be a lesson learned from neighbor Volkswagen and its highly-anticipated MQB project? "We don't focus on the competition. We are the only manufacturer that goes the whole nine yards."

What's more, Americans will see the three-cylinder first in the i8 electric sports car -- when paired with a hybrid drivetrain, it seems, the notion of a half-size Bimmer seems easier to swallow. The target for the three-cylinder will be 220 hp, while the electric motor will boost total output to a nice, even 300.

Three-cylinder engines used to reside in the mind of enthusiasts and consumers alike within the same section reserved for dollar store off-brands and reusable diapers: something so off-puttingly frugal as to be worthy of derision. But three-cylinders will proliferate because their abundance of economy and the science of full-throttle passing power have ultimately merged. Whether you're nostalgic for the venerable inline-six that put the Werke on the map, or whether you blew your college fund on rebuilding an M60B40 engine from an E31, all but guaranteeing tiny slivers of Nikasil inside your pulmonary nodules, there's little to fear from these motors except perhaps matters of principle.

But then again, they're not called the Motoren Werke for nothing.

By Blake Z. Rong