Acura stated very early on that LMP1 was their eventual goal, and therefore the LMP2 project could certainly be considered a toe-in-the water exercise leading up to
the LMP1; a means to an ends if you will.
Over the past two years, the program's partners
have gelled and they now have applied lessons learned to the new
ARX-02a LMP1. Seeing how effective a light weight LMP2 car could be up against heavier LMP1s on North American tracks didn't go unnoticed. And even while stepping up the next rung into the heavier LMP1 class, the desire to continue to want to take advantages of those benefits began to plant the seeds for the ARX-02a.
The ARX-02a has been designed to compete directly with the diesel competition maximizing the advantages afforded to the package and minimizing the disadvantages. And the use of the lightweight, normally aspirated, 4.0 liter LM-AR7 V8 is one of the pieces of the puzzle, but more on that in a moment. But we must consider first that this engine is certainly counter intuitive considering that in order to match to diesels in power it will have to rev higher at the sacrifice of reliability (it has a flat-plane crank after all) and there is little that can be done about the torque shortfall. It's a bit like showing up to a gun fight with a knife.
But ultimately it simply wasn't feasible for Acura to have developed a diesel engine to compete head to head with Audi and Peugeot given the time frame and the need to continue to develop the P2 effort. The same can be said for a hybrid gas-electric package (or turbo V8 for that matter), there simply wasn't time. This left Acura with few alternatives and it made sense to utilize what was already available to them, namely a "large" version of the existing LMP2 engine. Bored out to 4.0 liters, the LM-AR7 still carries over the IRL mounting points common to the LMP2 engine given that engine's origins as the stillborn 2006 Honda IRL power plant. More importantly, the LM-AR7 allows greater freedom in the placement of ballast compared to the competition's diesels.
So going into LMP1, Acura was aware that they needed to maximize the advantages they had considering their package. To that end, Wirth Research has designed the ARX-02a utilizing rear tires on all four corners. The immediate benefit is a 7% gain in contact patch area. But to make the fronts work effectively, a greater percentage of weight and downforce has to be applied to the front end of the car, more so than in a conventional car. Which gets us back to elements such as the light weight engine; in order to maximize this concept the entire car has to been designed with this in mind and this isn't a direction one would intuitively head given a conventional package.
A closed top design was considered, but upon further analysis there didn't seem to be any particular advantage. And in fact, given the car's theme, the increased weight and higher CG that comes with a closed top monocoque would have been cross purpose.
Nick Wirth admits that approximately 15 days were spent scale tunnel testing at the Auto Research Center in Indianapolis. The bulk of the Acura's aero development was handled through CFD by Wirth Research's sister company Digital Flow Solutions. And this is where Nick Wirth gets rather coy and won't divulge any of the (even mundane) details. Clearly Digital Flow Solutions has turned a corner in their CFD capacity to be able to so confidently reduce the amount of scale testing. All of the 2008 developments for the ARX-01b LMP2 were carried out via CFD and thus Wirth Research ultimately had their test case.
The ARX-02a has stepped up the level of detail design, this driven by necessity given the design brief. It will be interesting watching how this translates to on-track performance during the '09 season.
