Ford Performance has been granted an “erratum” fix by the FIA for its new Mustang GT3 ahead of this weekend’s FIA WEC weekend at Spa and IMSA weekend at Laguna Seca, RACER has learned.

The changes to the car are reliability-focused and have been made to rectify the issues surrounding the car’s boot lid and diffuser, which were becoming loose, damaged, or altogether detached during the races since its global debut back in January at Daytona.

The tweaks count as an official “out-of-cycle” homologation extension (erratum), which were signed off ahead of this weekend following a rapid turnaround by the FIA. The paperwork associated with these tweaks was submitted last Friday by Ford, allowing it to receive the green light before the WEC cars hit the track yesterday in Spa.

“These are changes we wanted to make as soon as possible,” Kevin Groot, Ford’s global sportscar racing program manager, told RACER. “And thankfully we have been able to make them prior to the Mustang’s Le Mans debut.”

Speaking about the boot lid fix, Groot explained that the issue had only occurred once during the car’s development and test ing phase at Paul Ricard. Ford believes it began to happen frequently during races when cars would follow the Mustang closely and disrupt airflow. It has been solved with new latches.

“We saw that the issue would stem from the crease at the back end of the boot,” he said. “We have improved its stiffness to prevent the folding from happening. In competition, we were getting air pushing up from underneath and it was causing that to break the bonds on the stiffening elements that were in place to stop it from folding.

“We tried a few things, but couldn’t get it to work, so we’ve had to put latches in there. Now we have a second set of latches from the top upper edge, so we don’t expect that issue to happen again. There are severe damage considerations around rear bumper contact that could destroy those parts, but in general, the boot lid should be secure in aero-type events.”

The new boot lid latches were in place for the WEC race at Imola and IMSA race at Long Beach, before the final changes to the diffuser were made in time for use in both championships this weekend.

Groot went on to explain that the diffuser issue is one that Ford and Multimatic had been working on for a long time behind the scenes. The issue stems from the fact that the diffuser was designed with the ability to ‘quick change’ during races in mind, weakening its mounting points.

“We’ve been chasing that issue for a while and taking little nibbles at it,” Groot continued. “But the short of it was that we’ve had to add a mid-mount latch, that’s a little further up. It’s an additional mounting fixture that just drops off the rear suspension pickup and holds the diffuser there.

“The diffuser was designed to prioritize ‘quick change’, which did not allow it to be secured well enough to the vehicle after contact. So now we’ve deprioritized that (quick change functionality) and made sure it’s attached well enough to make it through race and mild contact.

“Still, big contact will mess it up, and that’s how it goes, but we’ve taken the low-hanging fruit. And the FIA has been so helpful and cooperative in helping us get through this problem.

“It took a while, but we wanted to make the right fix. You can only touch parts once throughout the car’s cycle, so we had to make sure it was correct before we implemented it.

“Thankfully we made sure these changes came in time for Spa as the FIA didn’t want us to introduce changes for Le Mans, which we understand.”