Building the “best-handling sports car”

Acura’s new ARX-02a LMP1 car was unveiled on Monday at the American Le Mans Series’ Sebring test. The new car has been testing since early December and will be raced this year by Gil de Ferran’s team and Duncan Dayton’s Highcroft outfit. De Ferran is his team’s lead driver, partnered regularly by Simon Pagenaud and with IRL champion Scott Dixon joining them for Sebring and possibly the Petit Le Mans in October.

Highcroft’s regular drivers are David Brabham and Scott Sharp, and it was announced on Monday that Dario Franchitti would be the team’s third driver in this year’s season-opening Sebring 12 hours.

The new Acura P1 car has been designed and built by Nick Wirth’s (above) Wirth Research group in the UK and Honda Performance Development in California. The car is powered by a 4-litre, naturally aspirated V8 producing around 620bhp, not a turbo as rumoured. An intriguing feature of the Acura is that its 18in front wheels are the same dimension as the rears, requiring a complex power-steering system and producing close to a 50/50 front-rear weight distribution.

“The more rubber you get on the ground the faster the car is going to go,” says Wirth. “If we built a car that could efficiently use its tyres to the maximum of the regulations, we could put down up to a 10 per cent greater contact patch area. To make this work we had to load the front tyres far more than on a standard car, so we did a lot of work on weight distribution.

“With weight distribution, it’s not just a matter of loading up the front end. If you put all the ballast in the nose you’d make the car have a lazy response. It wouldn’t have the agility that helped our P2 car compete with a P1 car. So we had to try to minimise the negative effects and maximise the benefits.

“There were a number of factors conspiring against us. The first is that big front wheels are terrible for aerodynamics on any racing car, whether it’s a Formula 1 or an LMP1 car. When you put big front tyres on a sports car it tends to kill downforce, particularly front downforce.

“The effort we put into solving these issues was huge and it’s one of the most challenging and exciting projects I’ve been involved with. We put an extensive simulation programme in place and used all the tools we’ve developed over five years working with HPD in Indycars and the ALMS.

(Simon Pagenaud)

“There are no compromises in the design of the chassis,” adds Wirth. “We’ve pushed every single button we could with the engineering boffins. In fact, the only component that’s been carried over from the P2 car is the headlight bulbs.”

Wirth also explained the decision to build an open-cockpit car: “We wanted to maximise our resources, both in engineering and financially, and focus on what was important. A closed car is more expensive to build. It requires a lot of engineering resources to deal with the air-conditioning and doors, etc.”

In testing at Sebring on Tuesday, Pagenaud was able to turn a lap aboard de Ferran’s car that was 0.1 seconds quicker than Audi’s pole lap from last year, so the new Acura clearly has potential.

“It’s early days in this project,” says de Ferran. “There’s still a lot of work ahead. We’re just scratching the surface, particularly in the performance potential of the car, but already the performance is decent. One of the things that jumped out the first time I drove the car is it has a lot of grip in the corners and under braking.

“Making the decision to have the same size tyres all round has unearthed a lot of engineering problems and challenges that didn’t previously exist. One of them is the steering system because the loads are huge. The HPD engineers have developed one of the most complex and sophisticated power-steering systems. From a driver’s standpoint there’s a lot you need to adapt to.

“We’re trying to create what could arguably be called the best-handling sports cars ever made. It’s a fun project, but it’s hard work. [Team manager] John [Anderson] and the team have been burning the midnight oil, but that’s what we do. The creative process is a part of motor racing I really enjoy.”