The numbers are anything but a coincidence. Honda Performance Development’s new 2.4-liter twin-turbo V6 NTT IndyCar Series engine will debut in 2024 as, if all goes well in testing, a hybrid powerplant that makes use an energy recovery system made by MAHLE.
But for fans of IMSA’s WeatherTech SportsCar Championship, there’s no need to wait until 2024 as the first look at Honda Performance Development’s brand-new 2.4-liter TTV6 jewel will come later this year when the Acura ARX-06 GTP machine begins testing at IMSA-sanctioned outings.
Dubbed the ‘AR24e,’ the American-made IndyCar engine – designed and manufactured at HPD’s Southern California base – has been tailored to the needs of endurance racing. Paired with a 40hp ERS units supplied by Bosch and Williams Advanced Engineering, the internal combustion engine is expected to deliver 640hp in the class where 680 combined horsepower has been set as the limit when ERS is activated.
It’s believed the AR24e has different turbos than it’s IndyCar counterpart, and with a need to run for up to 24 hours at a time – well beyond the average open-wheel race that lasts approximately 1h50m – stronger internals with bespoke pistons, rods, and more would be well within the range of expected modifications.
Although HPD’s long-standing used of production-based TTV6s was thought to be the direction it would take with the ARX-06, the chance to repurpose its upcoming IndyCar motor in IMSA has provided a cost benefit where the same basic engine powers its involvement in both series.
“We’ve got to go fight some pretty impressive competitors, haven’t we?” HPD president David Salters told RACER. “So we need to make the best job of designing our racing car, and that includes the powertrain, which is fundamental for that. So we started with the rulebook thinking, ‘What do we need?’ And then the beauty of HPD is crazily we’re allowed to go off and do it. And that is part of Acura, part of Honda and its racing.
“So we came up with a brand-new racing engine, and it shares our IndyCar heritage and will share our IndyCar heritage, and he shares our sports car heritage and also it shares our Formula 1 heritage. So it’s everything we can think about putting in there to make the best powertrain we could. It’s a 90-degree V6. We’re trying to get the center of gravity [as low as possible] there.”
Rumors of the 2.4L IndyCar motor being built as a monoblock – without removable heads – have circulated since April. The low-resolution photo of the AR24e released by HPD suggests the rumors are true as no separation between the heads and block could be found in the image.
Sidestepping the question, Salters had fun dealing with the monoblock question.
“So, never ask a man about the size of his Johnson … so never ask an engine guy about the structure of his engine,” he said with a laugh. “There’s some things boys just don’t speak about.”
Where IndyCar sets a maximum rev limit at 12,000, the new GTP regulations call for a cap at 10,000, which places less stress on the valvetrain and other key rotating items within the engine.
“We have pushed the limit of the rules,” Salters said. “We’re trying to make the most compact, most efficient [engine], and we have to match this to the electrified part. So we did lots of thinking about what we needed this is a pinnacle-level sports car, basically an LMP1 car underneath to be to be really honest with you.
“So we started to think what do we need? So you have to package this to give you the best racing and so we thought about that, and for us, a small-displacement, high-revving V6 engine is best option.
“And also, if you look at Acura’s heritage, Honda’s heritage, what we do racing engines, we have a lot of experience in that arena. If you look at what happens now, with F1 engines and IndyCar engines, they last a long time. So we have a lot of knowledge in that area. We have a lot of work to do, but we felt that was the best we could do. And we want to show our technology.”
Through Honda’s sister championship-winning Formula 1 engine supply program, Salters says HPD’s first foray with GTP hybridization has benefitted from crossover development that will benefit Acura’s partner ARX-06 teams at Meyer Shank Racing and Wayne Taylor Racing when the prototype debuts in competition in January at the Rolex 24 At Daytona.
“Energy management, from our F1 side, we actually a while ago embedded one of our engineers on the F1 program” he said. “He did the energy management for Red Bull, so he’s back in our factory. We also have some guys that came over from the F1 program. So we’re using what we learned. The brain inside this [ARX-06] is an F1 ECU, so we have the ability to manage the powertrain and we wrote all our own software, which now seems a bit nuts.
“But we wrote with some very smart people inside HPD all the energy management software, all the ICE and control software and also the vehicle [software]. It’s got brake by wire. We’ve wrote all that software inside so we’ve used all our knowledge from energy management. That’s why actually why we go racing. So yeah, it’s legit.”