Honda Performance Development Opts for a Totally New Engine in Its GTP Racer
By David Phillips
DAYTONA BEACH, Fla. – There’s new, and then there’s brand new.
When the green flag waves on the 2023 Rolex 24 At Daytona, prototypes from Acura, BMW, Cadillac and Porsche will race in anger for the first time at the dawn of IMSA WeatherTech SportsCar Championship’s Grand Touring Prototype (GTP) class. But some of those prototypes will be newer than others; at least parts of them.
For, while BMW, Cadillac and Porsche opted to massage existing engines in their lineups to provide the internal combustion component of their new LMDh powertrain packages, Honda Performance Development (HPD) went where no other marques had gone by designing, building and developing its AR24e engine from a proverbial clean sheet of paper for the Acura ARX-06 to be campaigned by the Meyer Shank Racing and Wayne Taylor Racing teams. The resulting 2.4-liter, 90-degree, twin-turbo V-6 is the smallest displacement internal combustion engine developed by HPD for racing; one revving to 10,000 rpm.
A variety of factors entered into the decision to go with a bespoke engine, not least of which was there was only so much that could be done to develop the 3.5-liter V-6 that powered the Acura ARX-05 to three Daytona Prototype international (DPi) titles. What’s more, the powerplant on which the 3.5-liter engine was based is scheduled to be phased out of production.
“The easy thing would have been just to lift the DPi engine and plug it in,” says HPD President David Salters. “But that’s not why we do this: We do this to challenge ourselves. We said, ‘What can we do to make the best racing cars?’ We sat with the rulebook, did a load of simulations and just tried to make the best racing car we can (and) the best engine package to go in that car. It was a lot of work but it’s been great fun.
“Also, we had in the back of our mind that this may be the last (internal combustion engine) we make for racing. So the other brief I gave to our boys and girls was, ‘Let’s do the best thing we can.’ We wanted to celebrate all the experience and learning that we’d gathered and tried to put it all together.”
Of course, there’s more to a state-of-the-art racing engine than new blocks, rods, pistons, valves and camshafts. The hardware is just the start, witness the fact that the hybrid powertrain control system was also created from a clean sheet of paper, incorporating brake-by-wire and vehicle dynamics control systems written by HPD. Clean sheet of paper, perhaps, but not exactly created from thin air given Honda’s extensive experience with Formula One’s hybrid powertrain technology.
“We work with our colleagues in HRC (Honda Racing Corporation) which is quite special; a real privilege,” says Salters. “A number of years ago knowing that electrification was coming but also trying to grow the group, we embedded some of the HPD people in the F1 program to learn about energy management. That’s what you should do in your company, isn’t it? I have massive respect for our F1 colleagues with whom we have regular discussions. In terms of electrification and hybridization, that’s been extremely helpful. It’s been delightful, to be honest. a nice way of showing how if your company invests in different things, you can get different benefits.”
The powertrain is hardly all that’s new about the Acura ARX-06. The chassis is all new, although Acura’s relationship with designer/constructor ORECA is not. Although Acura considered all the IMSA-approved chassis makers in its plans for 2023, in the end they decided to stick with the manufacturer with whose chassis they won the DPi manufacturers titles in 2019, 2020 and 2022. And while much of the same design philosophy that guided the ORECA DPi chassis inevitably underpins the ARX-06, one would be hard-pressed to find a single carryover part (barring nuts and bolts).
Physically larger than the ARX-05, the ARX-06 accordingly sports larger brakes, heftier suspension and steering rack along with the beefy Xtrac gearbox mandated by IMSA and the ACO as part of the hybrid powertrain common to all manufacturers. And thanks to a less restrictive rules package, Acura designers (like their counterparts at BMW, Cadillac and Porsche) had considerable freedom in incorporating styling cues from their production cars into the distinctive appearance of the ARX-06.
Speaking of distinctive, the Acura GTP entry is particularly noteworthy for the peculiar shriek it emits under hard braking.
“As Freddie Mercury said, ‘It’s a kind of magic,’” says Salters. “We’re trying to do all sorts of things; that’s the fun of these cars. They are the future, so in terms of how we recharge the battery, brake and manage engine braking, it seems to make a weird noise. … The whole confluence of engine braking and (energy) regeneration and trying to manage the car into the corner with the electrification and all the other bits ends up making that noise … which is quite cool, isn’t it?”
The cool factor for all the GTP entrants will be on full display during Roar Before the Rolex 24 testing Jan. 20-22 at Daytona International Speedway. The 61st Rolex 24 is set to start at 1:40 p.m. ET Saturday, Jan. 28.