The claim has come from ex-Formula 1 aerodynamicist Nick Wirth who heads up CFD specialist Wirth Research in the UK.

Holden homologation team Triple Eight engaged Wirth Research to help design the aero package for the ZB Commodore ahead of its debut in Supercars in 2018.

In an appearance on The Hard Compound YouTube channel, Wirth explained that he exploited the VCAT testing system to ensure the car made more downforce in race trim than during the homologation process.

VCAT was a highly-controlled, airport runway-based testing system that was used by Supercars to test and tweak downforce levels for new models coming into the series.

It was used up until the end of last year when it was replaced by overseas wind tunnel testing.

Wirth claims that the use of control brake ducts during VCAT to accomodate the measuring equipment fitted to the suspension system created an “opportunity” to bend the rules.

In simple terms, he designed an aero package that would stall while the Supercars brake ducts were fitted, which meant the car would measure as legal, but create more downforce in race trim.

Wirth boldly claims that the difference was two and a half times more downforce – and that Triple Eight had no idea about the system.

“Probably there are going to be some people who hear this who aren’t going to enjoy hearing it, because I’m going to tell everybody how we used the rules to beat the rules,” said Wirth.

“We were approached by Triple Eight to try to help hold back the tide of Roger Penske and Ford in Aussie Supercars.

“The fun thing was how to do we do a car that’s a big step forward. I had an idea, because they had a flaw in the way they were validating the performance of the cars that we used to devastating effect.

“[Supercars] made one mistake, and the mistake was that they used their own brake ducts [for VCAT]. They were different to the brake ducts that we used on the real race bodywork.

“I said, ‘that’s an opportunity’.

“What we did was we did a CFD program where every single thing we did, we built models of the brake ducts and load cells that they used to measure the car [during VCAT], so we had a CFD model of that, and we had CFD models of the real bodywork with the real brake cooling system on.

“Basically we got the technology to look for anything that made a bigger difference between when you ran the standard load measuring brake ducts and the race system.

“We iterated towards a technology that when you put the load cells on, it switched our aerodynamics off. We essentially gave them a car that as soon as they put their load measuring equipment on, it stalled all of the downforce developing devices on the car.

“As soon as they took that stuff off, and we put our real stuff on, literally downforce was like two and a half times what had been measured.

“We did it by literally developing technology that used their won measurement system to defeat them.

“When the Triple Eight drivers drove our car for the first time they said there is no way this car is going to pass homologation. Not a chance. It is just nailed to the ground.

“It’s just a bit of fun, and probably there’s some people at Supercars that when they hear this story might grind their teeth a bit because I’ve never told anyone before.

“I’ve never told Triple Eight this story.”

The ZB didn’t actually win the Supercars title in its first year, Scott McLaughlin edging the drivers’ crown in the ageing FG-X Ford Falcon.

Ford and DJR Team Penske then unleashed their own aero monster in the Gen2 Mustang the following season, leading McLaughlin to two more titles.

The ZB, in the hands of Shane van Gisbergen, did finish the Gen2 era with two titles on the trot in 2021 and 2022.