Citroën’s new C4 model, named Picasso, comes in saloon car and family van versions. The saloon weighs in at around 1,400kg, the older model van tipped the scales at something in excess of 1,700kg, whereas the new version registers just under 1,500kg. The questions we posed were: what has happened to the weight and what developments have there been in the plastics engineering sector in the seven years that have elapsed between the two models.
Dimensionally, both vehicles are more or less comparable; the length is around 4.5m, the height 1.7m on the old model, 1.6m on the new one. The width has stayed virtually the same at 1.83m.
To give an accurate assessment of the weight, the engines need to be taken out of the equation because, as is evident from the disassembled models, the new version has a petrol engine, the old one a diesel. In the 2013 model, the weight of the engine and the exhaust system amount to 134kg and, in the diesel version, 183 kg. There is an extra third row of seats installed in the old model which accounts for 23.5kg. The remaining equipment, with gearbox, air conditioning equipment etc is comparable on both versions.This brings the comparable weight of the new model to 1,331kg-1,533kg, a weight saving of 13% or 200kg.
The French designers have made their greatest reductions in the steel parts. The body in white alone has shrunk by 57kg. The steering they have reduced to a third, from 68kg to 21kg (see steering illustrations below). The suspension is also lighter by around 10% or 20kg. Here, however, we are not able to estimate the extent to which the different motorisation has affected the reduction in weight.
All in all, Citroën has made some substantial savings when it comes to the proportion of metal. We were able to identify two fairly large metal sections that have been replaced with plastic. The tailgate, formerly manufactured from steel, is now largely made of plastic (see Plastic Omnium article).
The weight has shrunk by around 10%, from 39.6kg to 35.6kg. The frame now consists of two plastic shells, one inner and one outer shell (see photograph below). The technology on these vehicles features an inner panel made of thermoset sheet moulding compound (SMC) in a clam-shell design with a polypropylene (PP) thermoplastic outer panel, which is said to provide a Class-A surface finish.
A second component, the pedal support, has now been transformed from metal to polyamide (PA) and the original weight, in excess of 1kg, has now been cut back to just under 500g (see photos below).
The French were even able to optimise the proportion of electric and electronic components which are invariably prime suspects when it comes to responsibility for weight gain. The weight of these came down from 59kg to 50kg.
The proportion of plastic, as always excluding tyres, carpets and electrics, increased slightly from 13.14% to 13.4%. In absolute terms this means that 30kg plastic has been omitted, which means a minus of 15% (see tables).
Within the proportion of plastics there were some clear movements. As automotive manufacturers around the world can readily testify, PA clearly needed to provide reassurance of good suspension here too. Traditionally, the French are sparing in the use of PA, but in the little they did use, they have managed to achieve a reduction by a further half, from slightly over 20kg to just under 10kg. This is equivalent to 0.2 %.
Our Gallic neighbours have also increased the already high proportion of PP (102kg) by a further 5% to 107kg. Polyurethane (PU) is needed to guarantee good suspension. Here, the amount used fell from 18kg to 9kg, resulting in the PU PAD on the driver’s side weighing only an extra 1.2kg as against 2kg previously. It would appear that the French, conscious as ever of their well-being, require very little PU to create a comfortable seat.