<<BACK TO HOME

Renault Laguna


Renault wants the new Laguna to be in the top three for quality in its segment, backed up by outstanding crash safety.

Simon Bickerstaffe reports

Who supplies the new Laguna? Click here...


Premium cars are a big part of Renault’s product plans: it has spent €1 billion developing the new Laguna, with which the French carmaker is serious about setting new standards in quality and refinement.

But make no mistake. It needs to. The upper-medium segment has been shrinking for years and Renault admits the Laguna hit its sales peak in 2002. Cars such as the BMW 3-Series and Audi A4 now occupy the top spots. To add to the pressure, volume competitors such as the new Ford Mondeo have premium aspirations too.



The Laguna holds some aces though. The coupe is due at the end of 2008 and, judging by the concept shown at the Frankfurt auto show, it should look very good. A pair of new V6s – a 3.5-litre gasoline and a 3.0-litre diesel – are coming and optional four-wheel steering promises a sharp drive.

Then there’s safety. In 2000, the Laguna II was the first car to achieve a five-star Euro NCAP rating and since then Renault has been developing new technologies to ensure the new car represents a big step forward.

“We have to be clear about our priorities for the future,” says Jacques Faure, head of the safety department. “Quality is important, but we still want this car to be recognised as a benchmark in safety.”

The X91 programme – the Laguna III – lasted 32 months and involved 1,000 engineers, most at the Guyancourt technical centre. The car was developed from the platform of the old model, saving €100 million.

Weight reduction was a priority from the outset, despite the car’s slightly larger dimensions: Renault cut an average of 15kg across the Laguna line-up, thanks to a lot of optimisation work on the body in white, involving more than 4,400 virtual crash tests in one year. Seats, chassis components and even airbag casings are lighter.

New materials, notably ultra-high-strength steels, make the crash structure stiffer and lighter. “Laguna II used steel with a yield strength of 450MPa. That was brand new at the time,” says Faure. “Now we’re up to 1,200MPa.”



The old car had steel front bumpers, which are replaced now by a lighter, cheaper aluminium design. B-pillars and other structural areas also use higher tensile steels. A slight increase in performance brings a significant reduction in weight.

Information from real accidents guided structural development. “We work with PSA to collect accident data,” says Faure. “We analyse problems and make improvements. In frontal impacts, the previous model is good. We know that from the field results.”

So with that already high starting point, Renault redesigned the restraint system, complementing the enhanced crash structure. Double belt pretensioners have been fitted. The car has no knee airbags, however. Faure says pretensioners are more effective and cheaper.

Frontal impacts account for 50 per cent of fatalities in Europe, but as the number of five-star cars on the roads increases this should fall. “Side impact protection levels aren’t as good, so its share of fatalities will increase in the next few years,” says Faure. “That’s why we developed the new sensing system, necessary for the new generation of side impact airbags with dual chambers. We can protect at a higher speed than before.”

Virtual testing was improved, using human models to check the performance of crash test dummies in real-world tests. Faure needed to be certain that results were representative of real accidents. “Side impact dummies are not so biofidelic,” he says.

Simulations showed that the pelvis airbag needed to inflate earlier than before and needed to be stronger than the thorax bag. Subsequently, a multi-chamber airbag was developed with suppliers, triggered by dual sensors supplied by Autoliv.

“In this car the sensors are oriented at 45° so we can detect rotations – combinations of front and side impacts,” says Faure. “This is a better than normal planar systems.” Control algorithms for the sensors adapt airbag firing times to the severity of the impact.

Digital prototypes didn’t just help in development, but helped manufacturing too. For example, the seats in the old car were installed by hand, but using a virtual model, production engineers found that, with minor changes to the car, a robot could do the job.

Physical prototypes were still used, but fewer than before. Guyancourt built one batch for validation and another for pre-production. That’s considerably better than earlier programmes , which had three or four batches spread over several years.

Electrical faults were a common problem on the old car, so three electronic integration platforms were used to evaluate the entire system. Testing began early in the programme. The basic architecture is unchanged, but it uses a CANbus system and more functions are integrated into components.

Driving the car at the launch in Austria, it was clear that Renault has made real advances in perceived quality. The interior materials are high grade and fit and finish show huge advances on previous efforts. Cabin noise levels are also noticeably lower, with NVH levels under the bonnet reduced by a tuned steel link between the gearbox and battery to induce mutual mass-damping.

Acoustics are also helped by the more refined diesel engines. The smallest is only a 1.5-litre eight-valve unit with 81kW and 240Nm at 4,000rpm. This isn’t a lot on paper, but on a route that included the hills near Salzburg the little engine felt surprisingly strong.

True, it needed more frequent use of the six-speed gearbox than the 2.0-litre engines, but with less weight over the front wheels, steering felt much sharper. Economy is good too, at 4.9l/100km and 130g/km CO2.

It’s also noteworthy that Renault has paid special attention to the climate control system. Research revealed that some customers prefer a diffuse flow of cool air while in countries such as Spain, people want blasting, frigid air. A new system capable of both modes was developed with Nissan and Calsonic Kansei.

Luxury cars haven’t been a success story for Renault in the past, but this Laguna suggests the company now has the right development processes in place. The next models from its product plan should do better.

Who supplies the Renault Laguna?