Ahead of a public unveiling at The Quail, A Motorsports Gathering in Carmel as part of Monterey Car Week festivities, Acura has revealed new details about the ARX-06 LMDh car that will contest the IMSA WeatherTech SportsCar Championship’s new GTP class for 2023 and beyond. Acura also presented the car, which will be raced by current Acura teams Wayne Taylor Racing and Meyer Shank Racing with Curb Agajanian, without its previous camouflage, revealing it in a generic “presentation livery” that reveals much more about the car’s shape and design.
Acura’s ARX-06 chassis, built in partnership with ORECA, features an all-new 2.4-liter, 90-degree V6 with twin turbochargers that was developed and manufactured by Honda Performance Development and dubbed the AR24e. Acura says it is the smallest-displacement internal combustion engine HPD has developed for racing, but it easily meets the 500kW (670hp) target for the new formula. It will be mated to an IMSA/ACO-specified Bosch Motor Generator Unit (MGU), Williams Advanced Engineering batteries and Xtrac gearbox.
“We’ve taken the challenge presented by this new rule package from IMSA and the ACO, and developed what we believe is a very competitive solution,” said Pierre Descamps, who led HPD’s powertrain design team for the ARX-06. “We’ve gone in a new direction for HPD in the design of the ICE. It is still a V6, which of course for Honda is well-known, but we have incorporated several new elements which we believe will make best use of the electric MGU and battery pack. Our new engine will rev to the maximum 10,000 rpm set by the rules, so it also makes a wonderful sound!”
IMSA and FIA World Endurance Championship rules require manufacturers to use one of four approved prototype chassis, fitted with IMSA and ACO-homologated, manufacturer-designed and branded bodywork and engines. Acura chose to work closely with ORECA, the same chassis manufacturer it uses for its current ARX-05 Daytona Prototype international (DPi) car. Acura is currently leading the championship in DPi in the hands of Wayne Taylor Racing, with only Petit Le Mans left in the 2022 season.
HPD’s aerodynamics engineers and in-house CFD aero engineers worked with the Acura styling studio and chassis builder ORECA to help develop the styling and maximize the aerodynamic performance envelope of the ARX-06, while keeping it within the homologation boxes as specified by IMSA and the FIA. The new car bears a strong family resemblance to the DPi.
“The process we used in creating the exterior design for the Acura ARX-06 is exactly the same as how we create a new Acura passenger vehicle,” said Dave Marek, Acura executive creative director. “The same world-class stylists that lead Acura production car design created initial sketches, then pared those down to several potential designs. Next, we created a scale model, did aero and wind tunnel model testing, and brought HPD and our partner teams in for their feedback. The design continued to be refined throughout the testing and evaluation process, until we came up with a final treatment that met our performance goals while maintaining all-important Acura styling cues. It’s been an exciting process.”
The new LMDh cars, which are eligible for both IMSA’s GTP class and the WEC’s Hypercar category, are more complex machines than their DPi predecessors, owing not only to their hybrid powertrains and how those will be deployed, but also to other systems that must be integrated into the whole. As Acura notes, making it all work included developing a clean-sheet hybrid powertrain control system incorporating brake-by-wire and a vehicle dynamics control system, all of which was written in-house at HPD. This control system architecture, in the case of the ARX-06, was implemented on a Formula 1-spec ECU hardware platform. All of it was prototyped in HPD’s Hardware-In-The-Loop and Driver-In-the-Loop simulator systems.
HPD engineers tested the complete hybrid powertrain at the dyno facility at HPD, which can simulate key aspects of the cars during track running and the durability cycle, including running complete “laps” of a circuit for 24 hours — shifting, accelerating and braking is all reproduced on the dyno.
“The new Acura ARX-06 has elements of our Indy-winning technology, Honda Formula 1 technology and Rolex 24-winning technology in it,” explains David Salters, HPD president and technical director. “This was achieved using HPD’s world-class simulation, design, development and manufacturing technologies; that our own engineers have developed, tested and validated. We are very proud of that. Now the challenge and hard work really starts, including grueling 24-hour simulations, and learning how to maximize all aspects of performance.”
Acura, in conjunction with its teams, has already embarked on a testing program for the ARX-06, starting with shakedowns and tests in France a few weeks ago before shipping the car to the U.S., where it has seen track time at places such as Kansas Speedway to simulate Daytona.
The first IMSA-sanctioned test will be at Michelin Raceway Road Atlanta immediately after Petit Le Mans, where one of Acura’s teams will claim the team and drivers championships — Acura has essentially clinched the manufacturers title. The ARX-06, along with its competitors from BMW, Cadillac and Porsche, will make its competition debut at the Rolex 24 At Daytona in January. While Acura has committed to the IMSA WeatherTech Championship, it has not announced any plans for WEC or the 24 Hours of Le Mans.