The Acura ARX-05, built in partnership between ORECA and Honda Performance Development (HPD) is one of the most successful IMSA prototype racers of its generation. It has won two championships with Team Penske and laid claim to the Rolex 24 at Daytona thanks to Wayne Taylor Racing.
With the ARX-06 on the horizon with Acura’s impending LMDh programme, the ARX-05 will surely be remembered as a landmark machine once it becomes a museum piece. The same, however, can confidently not be said about its older, oft-forgotten sibling.
The HPD ARX-04b was Honda Performance Development’s first stab at designing and building a closed-cockpit prototype for use in IMSA, set to race in what was then called the United SportsCar Championship.
The reason this car doesn’t get mentioned an awful lot these days is simple: it only contested a single race and never returned to IMSA competition afterwards.
The HPD ARX-04b was created to be the successor to the ARX-03, which in various guises (both LMP1 and LMP2) has been in service since 2012.
Notably, it was going to be HPD’s first-closed cockpit prototype. All of the cars it had previously built featured open cockpits, but with closed cockpits rapidly becoming the norm (Ligier had already introduced the closed cockpit JS P2 and ORECA was introducing the 05 for 2015), the decision was an easy one.
The 04b was designed and built by Nick Wirth’s Wirth Research company, which was based out of Oxfordshire. Wirth is a well-known name in Formula One circles, previously having owned Simtek Grand Prix and also having worked for Benetton and Virgin.
Since 2007, Wirth Research had been a part of the Acura LMP programme in the American Le Mans Series and worked on both the Acura ARX-01 and the ARX-02.
For the HPD ARX-04b, Honda would be utilizing the 2.8 liter, twin-turbocharged HR28TT V6 engine. Based on Honda’s J35 production engine, the HR28TT had been in HPD’s LMP2 prototypes since 2011.
The team chosen to campaign the new, closed cockpit HPD prototype was Extreme Speed Motorsports. ESM was founded in 2010 by former Indy 500 polesitter and nine-time IndyCar race winner Scott Sharp and Ed Brown, CEO of the Patrón spirits company.
Sharp’s relationship with the Tequila Patrón brand, easily recognizable by its fluorescent green livery design, dated back to the later years of his IndyCar tenure, with Sharp sporting the company’s logo on his car from 2006 to 2009.
After his IndyCar career ended, Connecticut-born Sharp moved into the American Le Mans Series and took the tequila branding with him when he joined Highcroft Racing for two years, culminating in a championship-winning campaign in 2009.
It was here where Sharp first raced the Nick Wirth-designed Acura prototypes, with the high-nosed ARX-02b bringing him and David Brabham the title over De Ferran Motorsports.
For 2010, Sharp and Brown took their already existing relationship to a next level. Together, they founded the Extreme Speed Motorsports team.
Instead of continuing to race in the prototype classes, the team took a step down and opted to race in the GT2 category instead. It fielded two Ferrari F430 GTCs: one for Sharp and Johannes van Overbeek and one for Brown to partner multiple-time ALMS race winner Guy Cosmo.
The GT2 class in 2010 was a fiercely competitive environment for the new squad to be in, having to go up against factory efforts from the likes of BMW and Corvette, as well as Risi Competizione (Ferrari) and Flying Lizard Motorsports (Porsche).
Nevertheless, the highlight for the squad came at the season closer at Petit Le Mans, where Sharp, Van Overbeek and Dominik Farnbacher secured a second-place finish. Only the #4 Corvette finished ahead of them.
Two more years with Ferrari machinery followed, this time with the newly introduced 458 Italia GT2. The 2011 season produced just a single podium finish at Laguna Seca, but 2012 was far more successful.
After being awarded the win at Mosport following a disqualification for Flying Lizard, the team scored another milestone result at Petit Le Mans – winning the GT class. It was also on the grid for the memorable 2012 edition of the Twelve Hours of Sebring – a combined grid that saw the debut of the FIA World Endurance Championship.
In 2013, the team graduated up to the prototype ranks for the final season of the American Le Mans Series. It marked a reunion with HPD for Sharp, as the team would campaign two ARX-03b’s in the LMP2 category.
In a season where the Level 5 Motorsports team was their only full-season competition, ESM scored podium finishes at every round, peaking with a one-two finish on the streets of Long Beach.
The team subsequently moved on to the new IMSA United SportsCar Championship in 2014, campaigning the ARX-03b for another year. At the same time, the team was actively eyeing an entry into the FIA World Endurance Championship.
After winning at Laguna Seca, the team scaled back its North American operation to prepare for a full world championship assault in 2015, contesting both the Shanghai and COTA WEC rounds to prepare for the following season.
2015 was set to be Extreme Speed Motorsports’ most ambitious year to date. Along with a full, two-car effort in the FIA World Endurance Championship’s LMP2 category, it would compliment that with a programme in the North American Endurance Cup.
At the center of these two efforts would be the all-new HPD ARX-04b prototype. Built to LMP2 regulations, the car would be eligible to compete both in WEC and at Le Mans, as well as IMSA’s top prototype category.
“Couldn’t be more excited,” Sharp said in an interview with HPD’s Youtube channel in May of 2014, when it was announced that the team would be running the two cars in 2015. “We’ve had a long lineage with Honda from IndyCars to the sportscar programme. There’s obviously an incredible amount of trust and confidence in what Honda can do, from every aspect of the car.
“The engine, the management system: look at the car that we’ve been driving [ARX-03b]. It’s seven years old now and it’s still contending for race wins. To see the technology that has been learned and changed over those seven years, I think we’re as anxious as anything to see what the new car can unfold.”
At the time, Sharp also made no secret of his ambitions for ESM to race in the 24 Hours of Le Mans. The American driver already had one race start to his name in the French classic, dating back to 1999. The team, however, had not yet made the trip across the Atlantic prior to 2015.
“Patrón and ESM, we really want to go to Le Mans. This looks to me like a car that is designed to exceed at Le Mans, so we want to take advantage of that for sure. Whether it happens for 2015 or the following year, we’re going to do everything we can to get there as soon as we can.”
ESM had taken delivery of the ARX-04b in late 2014 and began testing ahead of its race debut at the 2015 Rolex at Daytona. At Daytona, it would be fielding a pair of cars. Once again decked out in the fluorescent green colour scheme, the #1 car would be piloted by Sharp, Ryan Dalziel and David Heinemeier Hansson. Ed Brown would share the #2 car with Johannes van Overbeek and Jon Fogarty.
It’s hard to say if any plans of glory in the WEC and at Le Mans went out the window at ESM when the Rolex 24 at Daytona rolled into town. One thing is for sure – the car’s debut certainly did not go to plan.
The #2 car was the only car running at the Roar, with the #1 car arriving later ahead of the race weekend. When it did arrive, it didn’t go smoothly. For starters, the new cars were found to be slightly over IMSA’s mandatory 940 kg minimum weight. This was not a problem solely reserved for the ESM cars, as other LMP2-based machines were also slightly too heavy.
On Thursday, however, things got worse when a manufacturing flaw in the bell housing was discovered with the #1 car of Sharp, Dalziel and Heinemeier Hansson, meaning that the car missed night practice and also did not set a time during the qualifying session.
With the #2 missing out on opening practice, the fourth and final practice session was the sole session in which both cars completed significant mileage simultaneously.
The #2 car didn’t fare much better in qualifying. Pole for the event went to, ironically, another Honda-powered LMP2 car. The #60 Michael Shank Racing Ligier-Honda, driven by Oswaldo Negri Jr., posted a 1m 39.104s to go quickest of all.
The #2 ESM ARX-04b was over three seconds behind with a time of 1m 42.390s, slower than the quickest of the Prototype Challenge qualifiers and thirteenth overall. The #1 car would meanwhile start the race from the back of the Prototype grid for what was increasingly looking like a tall order for the team.
After four hours, the race came to an end for the #2 car of Brown, Van Overbeek and Fogarty. The car completed 49 laps and retired with what was later reportedly deemed to an oil pressure problem. They became the race’s second official retirement after the DeltaWing gave up the ghost first.
The #1 car, meanwhile, was still running in seventh position overall, with Scott Sharp even briefly leading overnight when the cars battling for the lead made their pitstops. It even continued to run strong throughout the darkness, as the car seemed to remain impressively free of issues and was up to fifth overall by the halfway point.
Unfortunately, that wouldn’t last. After 389 laps completed, the #1 HPD ARX-04b of Sharp, Dalziel and Heinemeier Hansson fell victim to gearbox problems overnight and retired as well. The race victory ultimately went to the #02 Chip Ganassi Racing Riley-Ford of Scott Dixon, Tony Kanaan, Kyle Larson and Jamie McMurray.
Extreme Speed Motorsports came away from the 2015 Rolex 24 at Daytona with a double retirement, arguably not what the team had hoped to achieve upon debut for the ARX-04b.
Yet, despite the troubles earlier in the week and the #2 car’s early retirement, the run for the #1 machine prior to its gearbox failure showed that, despite its flaws, the package showed potential. However, as history would show, the car would not return to active competition again.
In the immediate aftermath of Daytona, ESM and HPD jointly opted to pull the ARX-04b from active competition for it to undergo further testing. Instead, the open-topped ARX-03b was called back into service for the second round of the Endurance Cup at Sebring while HPD worked on fixing the new car’s issues.
Those issues, as it was discovered, were mainly down to aerodynamics. The car was fast on the banks of the Daytona International Speedway, but needed more work with regards to front-end downforce.
Additionally, the car needed to be put on a further diet. It was slightly over IMSA’s 940 kilogram minimum weight limit at Daytona, but more work would need to be done to match the 900 kilogram limit set by the FIA World Endurance Championship.
Extreme Speed Motorsports’ Endurance Cup campaign came to an end after Sebring, with the team not racing at Watkins Glen and Petit Le Mans. It had to alter its WEC plans too, as the car also wasn’t sufficiently ready in time for the opening round at Silverstone. There, the old ARX-03b once again made another appearance.
Sadly, that was it for the HPD ARX-04b. The car never returned to competition, as ESM opted not to continue with the car and instead switched to Honda-powered Ligier JS P2s for the remainder of 2015.
The team continued in prototype racing for the next few years, although its relationship with Honda steadily lessened. It did score two more major wins with Honda power in 2016, as its Ligier JS P2 scored back-to-back victories in both the Rolex 24 at Daytona and Twelve Hours of Sebring. It also finished second overall at Petit Le Mans.
That did not prevent a switch from Honda to Nissan taking place for ESM. It had already made that move in the FIA World Endurance Championship in 2016 and in 2017, the Honda-powered IMSA Ligiers were traded in for the Nissan Onroak DPi for the final two years of the team’s existence.
Extreme Speed Motorsports would win the Twelve Hours of Sebring one more time in 2018 before Ed Brown’s Patrón company was bought by industry giants Bacardi for a reported $5.1 billion.
Patrón subsequently ended its motorsport involvement, leaving ESM searching for a new sponsor for the 2019 season. That sponsor was never found, forcing the team to close its doors after nine years.
Over at Honda Performance Development, they continued to work on the ARX-04b in the hopes of having the car returned to competition.
The car made headlines a few more times throughout 2015, most notably when news broke that the car would be taking part in the famous Pikes Peak Hillclimb with Justin Wilson set for driving duties.
That run would never take place, as the car suffered reliability issues (most notably with the turbochargers) that ultimately forced Honda to withdraw its entry.
HPD unveiled an updated version of the car in late 2015, featuring a revised front end and sidepods. Honda hoped that this would bring the car back to IMSA competition in 2016, but that never happened.
Michael Shank Racing carried out a test with the updated car at Sebring in March of 2016. Shank praised the improvements made on the car and used it for further tyre tests, but never raced it as he would switch to the GTD class with the Acura NSX GT3 for 2017.
While Shank did ultimately get back to racing a HPD prototype with the Acura ARX-05 in 2021, the ARX-04b was never seen again. It will forever remain a one-hit wonder.