Both the Mustang and Chevrolet Camaro will sport new bodywork this year after two rounds of wind-tunnel testing in the United States, and a season of parity controversy to start the Gen3 era.

The changes, though, are about more than just paritising the two models, with efforts also made to address pitch sensitivity for both, and an across-the-board increase in downforce, albeit one which is thought to be relatively small in magnitude.

Walkinshaw Andretti United was among the bulk of the southern-based teams to test at Winton on the Wednesday just passed, when Chaz Mostert drove his Mobil 1 Optus Mustang for the first time this year.

He said it felt “a fair bit different” compared to 2023 and while it is difficult to isolate exactly why, with just one test day in the book, he did give a positive initial assessment on pitch behaviour, while also praising Supercars for its expenditure on wind tunnel testing.

“I definitely think, last year to this year, we’re a little bit better in that area, for sure,” the two-time Bathurst 1000 winner told Speedcafe.

“It’s always a hard one to say what a Winton day’s like in general, but I think there’s definitely elements where you can feel some aero changes in the off-season.

“Hopefully, the Camaro’s the same, and it’s pretty cool to see those cars get in the wind tunnel and get the results.

“Where they’ve ended up, we’ll find out at the first round if it’s nice and close, but I feel like it’s definitely a step forward, and hopefully the lap times will be quicker this year for the cars as well.”

Worth noting also is that Mostert has a new race engineer and so too does James Courtney, who has also moved from Tickford Racing to the Blanchard Racing Team in the off-season.

Nevertheless, Courtney believes that the new aero has had an impact based on his test on Thursday, including in how the Mustang reacts to set-up changes.

“Straight away, it’s going to feel different; you know, a different car with a team and the way they go about things,” the 2010 champion told Speedcafe.

“But, aerodynamically, I’d say does react differently and also, with the way we’ve been doing the changes, the cars behave differently to the changes that they’ve made.

“So, I think it’s going to be really interesting, rolling into Bathurst – fast, flowing corners – it’s going to be good.

“I think the car felt really quite consistent with the way it rolls and the information we’re getting back as a driver was a lot clearer than what we had last year.”

The pitch issue was an instability under brakes caused by a stalling of under-car airflow when the nose dropped, which has been addressed by tweaked splitter profiles and tapered skid plates on both the Camaro and the Mustang.

The new aero packages generate more front downforce as a result of those improvements and hence changes to do the same at the rear in order to balance both ends of the cars, explained Supercars General Manager of Motorsport, Tim Edwards.

“Two key things were achieved at Windshear — one was taking away the sensitivity of the front of the car when it was in close proximity to the ground,” Edwards told the championship’s official website.

“That should give the drivers a more consistent feel with the aerodynamics.

“The other thing is the front changes led to the downforce number creeping up slightly. It’s nowhere near the levels of Car of the Future, but slightly more than last year.

“The drivers may feel they have more grip because they’ve got more downforce, but it’ll be more consistent.

“Every time they put their foot on the brake pedal, it won’t shift the aero balance as much as last year.

“To keep the same balance between front and rear, which is critical, we had to increase rear downforce slightly to keep the same percentage balance front to rear.”

While drivers and engineers may still be searching for an understanding of their new aero packages, the parity focus has now shifted to engines, as Ford/DJR works on a spec which will address what is said to have been a transient deficit relative to the LTR which powers the Camaros.

Courtney praised the new spec, having sampled both thanks to a rookie day for team-mate Aaron Love, while Supercars has since announced that it will hold ‘demonstration’ sessions at the Bathurst 12 Hour in order to collect more data.

The Repco Bathurst 12 Hour takes place on February 16-18 and the Thrifty Bathurst 500, which marks the official start of the Supercars season, on the following weekend.