13/1/12

Overview: BMW 3-series

BMW’s new Dreier follows the recent and welcome trend in automotive engineering in focusing on weight-saving as well as providing the expected raft of innovations from the electronics industry.

The new car is a little larger and roomier than its predecessor, by up to around 50kg lighter model-for-model, with most of this saving coming from the lighter bodyshell. The lightweight door structure is of interest: a new light-weight hinge assembly, in which bolts are replaced by screws, simplifies the assembly process and reduces vehicle mass.

Fuel-efficiency has improved across the range, not just because of lower kerb masses but also for a variety of other reasons: for example, deploying ZF’s newish 8HP transmission allows automatic versions to chase the engine’s torque curves more effectively than the 6HP used previously, offsetting internal pumping losses and making the automatic derivatives usually a little more frugal than the six-speed manual versions. The 8HP is available on all models. There is also a new petrol engine, of which more anon. Initially, four engines are offered — two diesel, two petrol.

All versions of the new 3-series feature Drive Performance Control as standard. This is a switch which allows the driver to swap between up to four driving modes, from sporty to economical. The four modes are Eco Pro, Comfort, Sport, and Sport + — Sport + is included as standard only on Sport models. In Eco Pro, the accelerator mapping changes so that a firmer push on the pedal is needed to extract the power that is delivered with a lighter touch in the other three modes: it doesn’t re-map the engine, but it might help less sensitive drivers achieve better fuel-economy. Eco Pro also alters the points at which gearchanges are indicated by the optimum shift indicator light on the dash; moresignificantly, though, it modifies the gearshift strategy on automatic models, and adjusts the power consumption of features such as the climate control and heated mirrors and seats.

BMW pulls its fuel-saving technologies together under the heading of Efficient Dynamics. Predictably, there are some new features under this umbrella. Automatic stop-start is fitted to all versions, manual and automatic, along with brake energy regeneration, on-demand control of engine ancillary components and low rolling-resistance tyres. As we have mentioned, kerb mass has been reduced, while improved aerodynamics bring the drag coefficient down to as low as Cd 0.26 — Mercedes-Benz territory. The new 3-series features a streamlined underside, covers which create a diffuser effect at the rear and ‘aero curtain’ air channels in the front apron which reduce the turbulence created by the revolution of the front wheels in their arches.

As we would expect, the new 3-series is fitted with electromechanical power steering; Servotronic speed-sensitive assistance is standard on the petrol models and optional on the diesels — odd.

All power-units used in the new 3-series are turbocharged and bear BMW’s Twin Power branding — this indicates either two blowers or a twin-scroll turbine, depending on the engine. The power-units used in the new car include the new four-cylinder N20 two-litre petrol unit, developing 245PS and 350Nm, in the 328i. This unit effectively replaces the six-cylinder three-litre atmospheric engines in the previous 325i and 330i, with inherent advantages in mass and fuel consumption; though with a claimed 0-100km/h time of 5.9s in manual form, it is quicker than either of its predecessors from a standing-start. Both manual and automatic versions of the 328i have NEDC fuel economy returns of more than 44mpg and CO2 emissions below 150g/km. The new unit is directly fuelled, with twin-scroll turbocharging, double-VANOS variable camshaft timing and Valvetronic variable valve-opening technology.

The 328i is one of four derivatives that are available at launch. The other three engines of which are familiar from the outgoing model. The other petrol engine on offer is the three-litre six-cylinder Twin Power turbo unit in the 335i. Diesel units are an improved version of the two-litre 184PS power-plant, which is used in the 320d, and the familiar 163PS Efficient Dynamics unit: this deploys reduced friction components and revised electronics, and is coupled with longer gearing by way of a 10 per cent. higher final drive. Previously only available as a manual, the 320d Efficient Dynamics is also now also available with the ZF automatic transmission, which offers the same 109g/km CO2 emissions level as the six-gang manual.

Three additional models are joining the range as this is written. The 316d and 318d are powered respectively by 116PS and 143PS variants of the two-litre diesel engine; a second version of the two-litre turbocharged petrol engine powers the new 320i, and is tuned to deliver 184PS and 270Nm.

In detail

The new BMW 3-series saloon features a stiffer body and an all-new chassis based on a longer wheelbase — now 2810mm, an increase of 50mm on the previous model. Fifteen millimetres of this goes into rear knee-room. Track is wider at both ends, by 37mm at the front and 47mm at the rear. Overall increases by 93mm, though interestingly the new car is 6mm narrower. Suspension is by aluminium torque struts, wishbones and swivel joints at the front and a refined version of the existing five-link arrangement from the previous 3-series at the rear.

Run-flat tyres (with no spare), linked to a tyre puncture warning system, are now fitted to every version apart from the 320d Efficient Dynamics. The rolling resistance of the tyres has been reduced by 15 per cent. compared with those on the previous model, with allegedly no loss of dynamic performance.

Optional equipment includes Variable Sport steering and Adaptive M Sport suspension with electronically variable dampers; these features interact with the Drive Performance Control and add the ‘Sport +’ mode.

The forthcoming M Sport derivatives will have lowered and stiffened sports suspension and larger, 18-inch M light alloy wheels.

Optional equipment includes the now familiar Bosch Park Assist, which allows the car to parallel-park itself, with the driver controlling the accelerator and brake. A reversing assist camera and surround-view cameras, which even let the driver see a virtual image of the car from above and the sides, are also available.

A full-colour head-up display is also on the options list. This shows current speed limits, the car’s current speed, and turn-by-turn instructions if a BMW navigation system is fitted. Dynamic Safety is another option: this tensions the seat-belts and closes any open windows or the sunroof (if it’s fitted and open) if an accident seems imminent. Internet access via the owner’s mobile telephone and BMW’s new Real Time Traffic Information service, which delivers warnings of traffic hold-ups and offers suggestions on how to avoid them, are among the media services available as part of BMW Connected Drive.

BMW U.K. has confirmed that towards the end of 2012 it will introduce four-wheel drive and hybrid powertrains to the 3-series saloon for the first time in Britain. BMW’s xDrive all-wheel drive system has been available on the 3-series in some markets previously, and has now been engineered for right-hand drive cars. It will be of particular benefit to owners who live in areas prone to extremes of bad weather.

The Active Hybrid 3 will arrive at roughly the same time, and will use the powertrain recently announced for the Active Hybrid 5. This pairs the 335i’s 306PS six-cylinder engine with a 40kW electric motor.

Munich production plant

BMW’s 3-series has been built at the Company’s historic Munich plant since 1975. Production capacity is currently 900 units per day; BMW aims to reach a peak output of 680 units per day of the new 3-series saloon three months after the start of production.

The new Dreier will be the BMW Group’s first model series to generate ‘virtually’ zero non-recyclable waste — less than eight grammes per vehicle — and the total annual output of such waste from the Munich factory has been cut to less than 1.5t.

With the launch of the new 3-series, a new large press will go into action at the Munich plant. This new facility, which will be capable of up to 16 strokes per minute and will have a throughput of up to 600t per day, develops press forces of between 650t and 2500t.

Installing the new press required a reconstruction of the entire 10,000m³ logistics warehouse. Because of the tight space constraints at the site, a solution had to be devised for conveying parts between the press shop and the body shop in the basement. Here, the focus was on consolidation of individual production operations. An underground conveyor system was installed which provides extremely efficient transport of the stamped vehicle parts to the body shop. A positive side-effect of this transport system is a big reduction in vehicular transport, with noticeable benefits for the environment and local residents.

The old body shop had to be completely demolished to cater for production of the new 3-series. The progressive dismantling of the old building began in 2007. The new building was constructed simultaneously over the top of the old, low-rise body shop. At the same time, new robots had to be installed, many of which had previously been used at the Leipzig plant. In addition, new laser robots and bonding robots have been installed. This modern, low-temperature process is used for twice as many operations as on the predecessor model, in some cases replacing conventional spot-welding. The new technique improves sealing and corrosion prevention.

In the paint-shop, new robots have been introduced for seam sealing, flange sealing and undersealing. A new foaming machine is used to provide firewall sound insulation. It foams the sound-insulating material in the cavity, resulting in improved insulation between the engine compartment and passenger cell.

The new 3-series is a very modular design, using component-sharing and production management to cut costs. Multiple models and derivatives are built on a single line. The front-end architecture of the new 3-series is identical to that of the 1-series, for example; these two model series also share common floor assemblies, which can simply be lengthened to cater for the different wheelbases of the different model versions.

The BMW plant in Munich has been building cars since 1922 and presently covers a total area of some 70ha. The factory is virtually in the middle of the city, a fact which has driven BMW to develop space-efficient production systems. In fact, production at the Munich plant is spread over five floors.

Over 60 per cent. of the vehicles produced here leave the plant by rail. There are 22 works buses for employees, operating on 46 different routes. In 2010, almost 206,000 vehicles and some 65,000 engines were built here.

BMW
320d
Audi
A4 TDI
Mercedes
C 220 cdi
Length 4624 4701 4591
Width 1811 1826 1770
Height 1416 1427 1447
Wheelbase 2810 2808 2760
Kerb mass 1420 1480 1525
CdxA 0.27x2.20 0.28x2.20 0.26x—
Swept volume 1995cc 1968cc 2143cc
PS/rpm 184/4000 177/4200 170/3000
Nm/rpm 380/1750 380/1750 400/1400
Nm/t 267 256 262
Urban MPG
(l/100km)
48.7
(5.8)
51.4
(5.5)
50.4
(5.6)
CO2 119 120 117
Emissions EU5 EU5 EU5
BMW 316d 318d 320d 320d ED 320i 328i 335i
Cylinders 4I 4I 4I 4I 4I 4I 6I
Block/head Al/Al Al/Al Al/Al Al/Al Al/Al Al/Al Al/Al
Valves 4 4 4 4 4 4 4
VVT IE IE IE
VVL Yes Yes Yes
Aspiration/geometry T/v T/v Tts/v Tts/v Tts Tts TBA
Fuel D D D D P 91 P 91 P 91
Fuelling d d d d d d d
Injection
pressure
160MPa 160MPa 180MPa 180MPa TBA TBA TBA
Bore/stroke 90.0/84.0 90.0/84.0 90.0/84.0 90.0/84.0 90.1/84.0 90.1/84.0 89.6/84.0
Swept volume 1995cc 1995cc 1995cc 1995cc 1997cc 1997cc 2979cc
Compression
ratio
16.5:1 16.5:1 16.5:1 16.5:1 11.0:1 10.0:1 10.2:1
PS/rpm 116/4000 143/4000 184/4000 163/4000 184/5000 245/5000 306/5800
Nm/rpm 260*/1750 320*/1750 380*/1750 380*/1750 270/1250 350/1250 400/1200
Maximum speed 124 130 145 141 145 155 155
0-100km/h 10.9 9.0 7.5 8.0 7.3 5.9 5.5
Urban MPG
(l/100km)
52.3
(5.4)
51.3
(5.5)
48.7
(5.8)
54.3
(5.2)
34.4
(8.2)
33.2
(8.5)
25.4
(11.1)
Combined MPG
(l/100km)
65.7
(4.3)
64.2
(4.4)
62.7
(4.5)
68.9
(4.1)
46.3
(6.1)
44.1
(6.4)
35.7
(7.9)
CO2 g/km 114 116 109 119 144 149 186
Emissions EU5 EU5 EU5 EU5
Transmission
— I
— II
— III
— IV
— V
— VI
— Final drive
M6 (A8)
4.002
2.109
1.380
1.000
0.781
0.645
3.231
M6 (A8)
4.002
2.109
1.380
1.000
0.781
0.645
3.231
M6 (A8)
4.110
2.248
1.403
1.000
0.802
0.659
3.231
M6 (A8)
4.110
2.248
1.403
1.000
0.802
0.659
2.929
M6 (A8)
4.551
2.548
1.659
1.230
1.000
0.830
3.077
M6 (A8)
3.683
2.062
1.313
1.000
0.809
0.677
3.909
M6 (A8)
4.110
2.315
1.542
1.179
1.000
0.846
3.231
Driven wheels Rear Rear Rear Rear Rear Rear Rear
Fuel tank 57l 57l 57l 57l 60l 60l 60l
Kerb mass † 1410 1410 1420 1415 1400 1430 1510
PS/t 82 101 129 115 131 171 202
Nm/t 184 227 267 269 192 244 264
Length 4624 4624 4624 4624 4624 4624 4624
Width 1811 1811 1811 1811 1811 1811 1811
Height 1429 1429 1429 1416 1429 1429 1429
Wheelbase 2810 2810 2810 2810 2810 2810 2810
Track
— front
— rear

1543
1583

1543
1583

1543
1583

1543
1583

1543
1583

1531
1572

1531
1572
Steering ratio 15.1:1 15.1:1 15.1:1 15.1:1 15.1:1 15.1:1 15.1:1
Brakes
— front
— rear

Dv
Dv

Dv
Dv

Dv
Dv

Dv
Dv

Dv
Dv

Dv
Dv

Dv
Dv
Tyres 205/60R16 92W 205/60R16 92W 205/60R16 92W 205/60R16 92W 205/60R16 92W 225/50R17 94W 225/50R17 94W
CdxA 0.26x2.20 0.26x2.20 0.27x2.20 0.26x2.20 0.29x2.20 0.29x2.20 0.30x2.20
† DIN kerb mass. For E.U. kerb mass, add 75kg.
* With temporary overboost.
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