Alfa Romeo 4C uses a mixture of composites and traditional materials in production
The £50,000 Alfa Romeo 4C has been conceived as a supercar-beating sports car whose combination of light weight, modest power and agile handling might be expected to see off heavier, more powerful and pricier exotics.
“We could see a situation where a 4C driver might easily be quicker on tight, twisting roads, like a mountain pass, than a supercar like the Bugatti Veyron because of its agility and compact size,” says European sales boss Louis-Carl Vignon.
Last week Alfa lifted the lid on some of the technical highlights that might deliver this giant-killing performance, including the first look at its carbonfibre tub, alloy subframes, running gear, composite panels and lightweight glass.
Although the carbonfibre tub makes up just 10 per cent of the 4C’s kerb weight, it accounts for a quarter of the material volume. Aluminium (subframes, suspension and engine block/transmission casing) accounts for 38 per cent of the kerb weight and steel (engine/gears, suspension, rollover protection) 23 per cent. The composite body is seven per cent.
The main figures are a 65kg carbonfibre tub and an 895kg dry weight, which is expected to nudge towards 1100kg as a final ‘in-service’ figure when liquids and a fuel load are added, together with the legally required 75kg driver with luggage.
Alfa Romeo has targeted a weight-to-power ratio of below 4kg/bhp. At the quoted dry weight, Alfa says it has achieved 3.85kg/bhp, sufficient for 0-62mph in 5.0sec. Top speed is 155mph.
Trying to avoid the obvious comparison with the steel-bodied Porsche Cayman/Boxster, Alfa is proud of the 4C’s performance. “We are faster than other similar cars,” says Vignon. “The performance is quite something. This is a real pure-bred Alfa.”
The engineering spec is a long roster of lightweight materials. The sheet moulding compound (SMC) composite used in the body is a special lightweight formulation. Even the glass has been pared down to keep weight low.
Many aspects of the 4C are simple. The steering is unassisted, saving the weight of hydraulics, and the electrical system is relatively simple, featuring fewer than 10 ECUs. The manual air-con, for example, was chosen partly because it doesn’t need an ECU and keeps the engineering lightweight.
Alfa has confirmed that the first UK cars will arrive in late August, with customers of the first, higher-spec Launch Edition models possibly taking delivery in September.
Engine
Alfa is at pains to point out that the 4C will be powered solely by a four-cylinder engine mated to a dual-clutch automatic gearbox. Rumours persist, however, that a V6 will come eventually. ìThe four-cylinder is perfect because it gives us the performance of a six but is much lighter, says European sales boss Louis-Carl Vignon. Emissions are better, and in many European markets that is becoming more important, even for sports cars, for tax reasons.
The 237bhp, 1.7-litre turbo engine is a lightweight version of the 1750TB engine in the Giulietta, with an alloy block in place of iron, which saves 65kg. Project engineer Domenico Bagnasco says the dual-clutch automatic gearbox has been retuned for sharper responses.
Suspension
The suspension is steel wishbones at the front and alloy struts at the rear. The front suspension is bolted directly to the carbonfibre tub, rather than hung off the front subframe. To ensure dimensional accuracy for the suspension set-up, the mounting faces are machined to an accuracy of microns. The front subframe supports the body and radiator and doubles as the crash structure, which crumples to protect the tub from damage.
Project engineer Domenico Bagnasco says the rear strut design is different from typical practice, with lower mounting points internally for the damper units and lower spring mounts to get the package height down in the low-slung 4C. Struts are also used at the back on the Porsche Boxster and were fitted to the fabled Lancia Delta Integrale.
Carbonfibre tub
The 4C’s carbonfibre chassis will have the highest production volume of any to date, with output planned at a maximum of 16 per day. That’s about 3500 a year. Supplied by Adler Plastics, an Italian carbonfibre specialist based near Naples, it’s the firm’s first road car tub. Adler normally makes racing and aerospace parts and, for Maserati, carbonfibre trim. The tub uses ‘pre-preg’ carbonfibre, which is hand-laid in a one-piece mould and oven cured in vacuum bags. It takes 90 man hours to create. Although this display tub has an all-over polished finish, production cars are polished only where carbonfibre is visible — on the inner sills and central structural backbone.
Body production line
A new building has been converted at Modena to fit out the carbonfibre tub with sub-components and clothe the structure in composite body panels. Panels are painted off-site at a Modena specialist that also sprays Maserati’s special body colours. There are 864 components in each 4C, 136 of them in the main tub/subframe/body structure.
Uniquely, the 4C is the first car to have its body assembled at Modena using composite panels shipped in from a supplier. All previous Maserati models have been assembled from built-up bodies supplied by local coachworks. The GranTurismo, for example, comes in from Turin. To ensure the quality of assembly of the tub, subframes and panels, a digital measuring arm checks 350 points on each completed shell.
Final Assembly
The 4C final assembly line occupies space previously used for the Maserati Quattroporte; production of Maserati’s new four-door has moved to Turin. There are nine main assembly ‘stations’, each manned by between two and three workers, who have 14 minutes to perform multiple assembly operations. The 14-minute ‘cycle time’ is long by volume car factory standards; typically, they are as low as one minute. But 14 minutes has been the standard Maserati cycle time at Modena, so it is also adopted by Alfa. Station 4, where the engine and gearbox are installed, is one of the most time consuming. Overall, it takes between 20 and 25 hours to complete the build, which is spread over about three weeks. By comparison, a Maserati takes about 60 hours over two months.