Right up through the 1970s, the word "prototype"indicated just that, a car that could be developed for use on the road by a manufacturer. Many were licensed and could be legally driven on the road.
The Acura ARX-05 is more than just a nod to this prototype tradition. In both styling and propulsion, the connection to Acura passenger vehicles of today – and tomorrow – is readily apparent.
When Acura and its North American racing subsidiary, Honda Performance Development (HPD), made the decision to return to IMSA prototype competition in time for the 2018 season, it set off a development process that resulted in a clean sweep of the 2019 IMSA WeatherTech Sports Car Championship Daytona Prototype international (DPi) titles: Manufacturers’, Drivers’ and Teams’.
The two-car Acura Team Penske effort has amassed an impressive record of four wins, nine poles and 18 podium finishes in just two seasons of WeatherTech Championship competition. But the process that helped generate these results began several years earlier.
In The Beginning…
Acura’s preparations for entry into top-level IMSA prototype competition began when the FIA, ACO and IMSA formalized the current LMP2 regulations, which also would form the basis for DPi, in 2016.
At that time, HPD was already active in IMSA competition, supplying engines to both Michael Shank Racing and Tequila Patron ESM, scoring four wins that year, including the Rolex 24 At Daytona, Mobil 1 Twelve Hours of Sebring Presented by Advance Auto Parts and Motul Petit Le Mans.
Meanwhile, the Acura NSX GT3, set for a 2017 race debut in the GTD class, was in the midst of an intense development program under the direction of a separate working group within HPD.
"Throughout 2016 we started interviewing [chassis manufacturers] and looking at the products they’d have," remembered HPD Race Team Leader Allen Miller. Miller and Acura DPi Program Manager Matt Niles, who were both part of Acura’s successful American Le Mans Series program from 2007-09, made visits to all four approved chassis constructors, before partnering with ORECA late in the year.
By the Spring of 2017, Acura finalized its other major partnership, with Team Penske, setting the stage for a year of intense design and development among all three organizations. HPD, Penske and ORECA all worked together in developing the chassis to Acura’s needs, according to Niles.
"Starting pretty early in 2017, we were having weekly calls involving all three of us to sort through crunch lists on what to do," he said. "Because we had one team, it was easy to involve them and work together. We all brought our own resources and expertise to the table, so we were able to pick and choose what was the best way.
"There were a lot of changes compared to the [original] LMP2 car."
The Design Stage
Next came the car’s bodywork and overall appearance. IMSA’s DPi-specific styling requirements allowed HPD to work hand-in-hand with Acura’s design team to create the look for the ARX-05, led by Acura Global Creative Director Dave Marek.
"We created a variety of initial sketches, then pared those down to a handful of potential designs. Next came aero and wind-tunnel model testing, and time for the [HPD] engineers to have their say," Marek recounted. "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 Acura styling cues."
Compared to other DPi designs, the ARX-05 is notable for its aggressive, aero-heavy front end featuring a formula-car-style wing that diverges notably from existing DPi entries, and the company’s trademark "Jewel Eye" headlights.
The 3.5-liter, twin-turbocharged V6 engine, derived from the Acura passenger vehicle line, had already proven its success in the previous-generation Ligier and HPD chassis, although it was the first time in an ORECA, which was originally designed for the LMP2 class-spec normally aspirated Gibson V8 engine.
While early CFD studies on the aero proved successful, Niles and Miller said the biggest challenge was achieving sufficient cooling to the production-based, V6 Acura AR35TT twin-turbo engine.
Miller said IMSA’s DPi homologation process was also very thorough, although HPD’s previous experience in working with the sanctioning body made it relatively seamless.
"With LMP2, with the homologation, it was, ‘Here’s our engine, here’s our car.’ It was basically a straightforward, 10-page document. But for the ARX-05, it was detailed and very specific," Miller said.
Niles added: "We were obviously running [Honda-powered Ligier] LMP2 cars against the DPs in 2015 and 2016 and we developed a good relationship with IMSA. They were part of the [development] process, such as the dyno testing, and observed some of the wind tunnel testing. Also, going through a similar process with the Acura NSX GT3 car [earlier], it helped make things smoother with the DPi car."
Success Comes Early
Just four races into its first season in 2018, Acura Team Penske’s Ricky Taylor and Helio Castroneves delivered the ARX-05’s maiden victory at Mid-Ohio, in a dominant sweep of the weekend for the manufacturer that included pole, most laps led, and a 1-2 finish, with ATP teammates Dane Cameron and Juan Pablo Montoya finishing second.
Everything came together in 2019, with Acura scoring three wins and nine other podium results to claim the DPi Manufacturers’ Championship. Cameron and Montoya took the Drivers’ Championship, with Castroneves and Taylor finishing third; while Acura Team Penske completed the sweep with the Teams’ title.
"We started this motorsports journey in 2017. To be here and winning championships after just three years is just incredible," said Jon Ikeda, vice president and Acura Brand Officer. "Roger Penske and his team are the gold standard of the industry. We partnered with winners, and we’ve gotten great support from everyone at HPD with their tireless efforts. Acura is a performance brand. We’re here to win races and compete for championships. And we’re not done yet."