The Pirelli World Challenge has seen a massive transformation in the last 12 months, with the introduction of FIA GT3-spec machinery that’s revitalized its once-stagnant GT class.

From Audi R8 LMS ultras to Ferrari 458 Italia GT3s and being the only North American series featuring exotics such as the McLaren MP4-12C, Lamborghini Gallardo FL2 and Bentley Continental GT3, the series has reached new heights, thanks to its move towards the worldwide platform.

“It’s taken us 18 months to fully integrate them in the homologated format,” World Challenge Competition Director Geoff Carter told Sportscar365. “We tried to run them in a World Challenge aero spec [in 2013] and it just didn’t work. You’re either all in or all out.

“Going with the full [FIA GT3] spec, we’ve had great teams, the car counts are up and the racing is really good.”

The grid has seen a dramatic increase, with 23 GT/GT-A cars entered for this weekend’s season finale at Miller Motorsports Park, compared to a mere six GT cars for last year’s final round at Houston.

While the content has been there all year long, the series’ technical staff, led by Carter, have battled the much-talked-about Balance of Performance between the FIA-homologated GT3 cars and some of the remaining legacy World Challenge-based GT cars, such as the Cadillac CTS-V.R.

“We’re still working on the balance with the World Challenge GT cars,” Carter admitted. “The worldwide recognized BoP, whether it’s FIA or SRO, it’s pretty well established. It’s just when you have that wild card of a World Challenge GT-spec car.

“We’ve done very few [BoP] adjustments with GT3 cars. Frankly, we’ve had to just try to keep balancing the Cadillac. It’s difficult because we’ve had trouble getting it correct, whether it’s above the line or below the line.”

Carter said some of the biggest World Challenge-imposed BoP changes on the GT3 cars have primarily been to acclimate them to North American racing, particularly with the series running a large number of street circuits.

“The DNA of these cars are more [suited] for Paul Ricard or Monza,” he said. “You take these cars to Detroit or St. Pete and the dampening and gear ratios are all different. We’ve seen some differences there.

“We’ve held true to the FIA homologation in terms of gears and diffs. We did open up the dampers… but we’re in discussions internally whether to go back to the FIA-homologated dampers and are working with the manufacturers on that particular issue.”

One of the things Carter and the World Challenge technical staff didn’t expect, though, was the rapid evolution of the GT3 cars, which has seen teams quickly come to grips with their machinery, despite the majority still only being in their first season of competition.

“We didn’t anticipate the GT3 teams would develop as quick and as good as they did,” Carter said. “We missed this crossover so that’s why we saw a bit of a deficit in the Cadillac and have fixed it for this last race.”

Should the much-rumored Cadillac GT3 car, which was allegedly spotted last week en route to BoP testing overseas, materialize, Carter said it would help achieve an even closer balance in the 2015 regulations.

“The whole platform of the existing CTS-V is completely different to the GT3 platforms in any configuration,” he said.

“As soon as checkered flag falls at Miller, and if at some point Cadillac ends up with a GT3 car, and it ends up being homologated and balanced abroad, then they’re right back in the wheel house.”

In addition to the potential Cadillac ATS-V, the series could welcome a number of other new GT3 cars to the mix next year on a full-time basis, including Nissan’s GT-R NISMO GT3 and the BMW Z4 GT3, the latter which made an early-season appearance in the hands of Turner Motorsport.

“We would love to have a Nissan, or two or three,” Carter said. “We would love to have BMW. Those are the two big ones that come to mind that we’ve seen in the past and we would like them to come back with a full-season effort. We think we’re close to making that happen.”

With Carter targeting a minimum of 30 full-season GT/GT-A entries next year, the future for GT3 in America appears to be bright, especially following IMSA’s move to adopt the same spec for its GT Daytona class beginning in 2016.

“[GT3] has exceeded our expectations by a magnitude of ten,” Carter said. “I think it’s important, as a series, to provide a platform for the manufacturers and different brands to create value for them to want to be here and to create some value in our brand at World Challenge.

“We’ve worked very hard through the marking efforts and through our collaborative efforts with our promoters and the manufacturers to create that value. It’s one step at a time but it’s seemingly better every day, which is good for us.”