Good things come in threes

The next wave to sweep over the car industry won't be electric cars and it won't be fuel cell cars, either. The biggest names in the car industry have predicted that three-cylinder engines will burst across the production-car world within five years.

Mercedes-Benz has admitted a three-cylinder turbo engine will be on sale all the way up to the C-Class within five years, while BMW is developing an all-new car to suit the quirky noise, vibration and harshness characteristics of three pots.

The Volkswagen Group already has three-cylinder petrol and diesel engines on sale in Europe, while both Daimler (with smart) and BMW (with Motorrad) have three-cylinder experience.

"A three-cylinder engine in the C-Class is quite conceivable," Daimler's board member in charge of R&D, Dr Thomas Weber hinted at this week's Zero Emissions technical seminar. But his Daimler strategist Johannes Reisenrath went even further.

"Logically, if we go from eight to six cylinders with the same output to help economy, and we go from six to four cylinders, then four has to go somewhere, too," Reisenrath explained.

"The combustion engine is getting more and more efficient with torque and there is always a demand for lower consumption.

"Right now we can do three cylinders with 1.2 litres, so we can have 120kW with a turbo-charger, plus 200-250Nm of torque, which is enough to drive a mid-sized car like the C-Class very well. It also has a six percent fuel-consumption benefit, and with 95 grams of CO2 fleet fuel consumption as a target, that's an option we have to consider."

If those sorts of specifics make it sound a lot like Benz has taken the idea much further than just R&D, then he went on to confirm the suspicion.

"Mid-size cars in the future will be much more aerodynamic, and the three-cylinder fits perfectly with that idea, too. For sure, we will have one on sale in the next four to five years.

"If you look at the shift in the market since CO2 regulations came into place, four-cylinder engines are now up at 40 percent of the market in the US. Some car makers are 80 percent four-cylinder and that creates a place for three-cylinder engines."

But don't expect them to be slow, because Benz admits people want their fuel economy savings to be wrapped up in cars that are just as fast as their current cars.

"From driving some of the earlier three-cylinder cars, they have a nice torque punch. We are much more advanced in turbo-charging and gearboxes, so they will be even better next time."

BMW drivetrain engineer Wolfgang Nehse refused to confirm the production future of BMW's three-cylinder engine, but other sources have confirmed the next 1-Series has been engineered to cope with the different NVH outputs.

"Maybe in the future a three cylinder is possible but it's not only a matter of developing the engine," Nehse said. "We have to develop a whole new car to get the best acoustic and vibration, because three cylinders have a particular character.

"But three cylinders are nice engines," he said. He should know. He developed the three-cylinder engine for BMW's motorcycle division, Motorrad.

"In our strategy, we start to introduce new technology in the eight cylinders then the six and the four and maybe even less."

And seeing as NVH for a three-cylinder engine is posing a challenge to the German companies, perhaps they should turn to the east and check out Honda's work with its VCM V6 in the Accord -- there's a car that adjusts acoustics when the engine is operating on just three cylinders.

While the Germans are pondering, have the Japanese already licked the problem?

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