SUPERCARS’ recent bout of barometric pressure testing did find discrepancies in how altitude affects the performance of the Ford and General Motors engines.

The high-tech procedure was set up at Cragsted Race Engines’ Queensland facility, with testing last week focusing on Ford’s 5.4-litre Coyote and this week the GM 5.7-litre pushrod.

Findings pointed to the Coyote’s output decreasing relatively evenly across the board at low atmospheric pressure, whereas the GM dropped off more heavily in the low-rev range and less so in high revs.

Specifically, V8 Sleuth sources say the GM was found to be at a deficit below 5200rpm but at an advantage from 6300rpm upwards – which might play into the ongoing narrative about Ford’s peak speed being down.

A proposed solution involved a tweak to the Ford’s variable cam timing and a change in restrictor size from 50mm to 51mm.

Supercars found that to reduce, albeit not entirely nullify, differences at both ends of the rev range.

Craig Hasted’s work to deliver the pre-Bathurst testing has been applauded. Pic: Ross Gibb

However, implementing that solution in time for this weekend’s Repco Bathurst 1000 was not as straightforward as it might seem to the outside world, given how the Teams Racing Charter legal document restricts in-season changes to things like the Engine Specification Document.

Once into the relevant calendar year, a 75 percent vote in favour is required to change the ESD. That becomes 100 percent at events for which Supplementary Regulations have been issued.

Restrictor size is an item in the ESD; variable cam timing is not.

Hence the need for negotiations involving GM, Ford and Supercars in order to reach an agreement – something which has not occurred at Mount Panorama.

Hence provisional pole man Brodie Kostecki’s frustration that despite a solution being formally identified to improve parity, it will not take effect this weekend.

“It’s a bit disappointing that nothing has been done about it after a report has been published… at the end of the day, the system is pretty flawed,” he said.

It should be noted the barometric testing only focused on inlet pressure and not exhaust – though inlet is the bigger influence.

Supercars track action resumes today with Practice 5 from 10:05am local/AEDT.