Three-cylinder versions of the BMW 3 Series are technically plausible, but the company has “question marks” over whether such a driveline would be accepted by the market despite a wide range of potential benefits, according to company corporate communications manager and powertrain specialist Manfred Poschenrieder.
This transversely-mounted engine will in time power a whole suite of front-drive BMWs, including the next 1 Series due around 2017.
Furthermore, as the i8 petrol-electric sportscar proves, three-cylinder engines with 150kW or more are eminently possible right now, although the i8 uses a high-voltage generator to help supplement the bigger turbo.
But the notion of putting such an engine into a 3 Series, even a tuned variation of the current unit mounted longitudinally, remains a subject of contention despite of its environmental benefits, low weight and — interestingly — what BMW perceives as aural and emotional benefits.
"At the moment its a pretty simple answer,” said Poschenrieder. “At the moment it is our entry level engine which supports us to reduce our CO2 range targets in future, mainly with small vehicles, like the Mini and anything around the UKL platform.
“All the other models, probably 1 Series could get this, but above this I would put a question mark, though it depends on how the market receives it.
“Sometimes it is based around emissions taxes. We have countries specifically looking for that, so this is all depending, but 3 Series? At the moment I would rather say the focus in on cars below the 3 Series.”
Interestingly, Poschenrieder said that despite the brand’s current reluctance for a three-cylinder engine in the 3 Series, such an engine actually had some less-tangible benefits. Rather than somehow cheapening the badge, it could be quite the contrary, he said.
“To answer this a little bit more, I would rather say if you put a customer in a three- or four-cylinder with the same power outputs and the customer didn’t know which was which, they would prefer three cylinders because the acoustics, response and behaviour of the three-cylinder is related to the six cylinder.
“It is a cut in half version which means it comes on the same frequency level in sound development, but is just rougher because it has a half ignition timing. But it develops sound as a six does and this gives it a nice and easy sound frequency and easy torque development.
“So as long as we use three-cylinders it makes sense but the borderline would be the power-to-weight ratio, because there is an area where it makes no sense to put a small engine into a big car.”
As we reported earlier, BMW has also put a line through a front-drive 3 Series, with BMW corporate and government affairs spokesman Kai Lichte stating that cars of this size and above would remain rear-drive in perpetuity.
“We will stick to rear-wheel drive from the 3 Series onwards, that’s for sure,” he said. “It’s really hard to imagine having a 3 Series on a front-wheel drive platform. We don’t see it for the next 10 years that’s for sure.”