BALANCE of PERFORMANCE (BoP) regulations for GT3 and GT4 vehicles competing in the 2019 Liqui-Moly Bathurst 12 Hour have been released to teams ahead of the January 31 – February 3 event.

BoP is the mechanism by which such a broad variety of competing vehicles can compete on a level playing field in any given race.

Essentially, it allows a front-engines V12 Aston Martin Vantage compete with a V10-powered Audi R8 LMS with the engine mounted behind the driver and a Porsche 911 GT3R with the flat-six engine hanging over the rear axle – and everything in between.

BoP for GT3 and GT4 events are set by SRO Motorsport Group Technical Director Claude Surmont, who oversees the technical requirements of each category SRO manages – including the Intercontinental GT Challenge of which the Bathurst 12 Hour is the opening round.

SRO uses an extensive system to set the BoP for all competing vehicles, starting with each model’s homologation as a GT3 or GT4 contender.

A group test using the SRO’s own drivers is undertaken to measure each model against each other, assessing strengths and weaknesses and where the cars could potentially be changed to bring them closer together.

Extensive computer simulations, using the homologation and testing data, are also used to help define the performance adjustments.

The system uses a variation of weight, ride height, air inlet restrictions, refueling rig restrictions and, in the instances of turbocharged cars, maximum limits of turbo boost pressure across the rev-range to manage performance across each vehicle.

While added weight will alter the overall performance of the car, the air restrictor and turbo boost settings change the horspower and torque it produces. Mandating a minimum ride height changes the handling characteristics – cars with more downforce will be given a higher minimum ride height setting to balance that with cars that may not produce the same figures.

Changing the rate at which the car receives fuel can either make pit stops quicker or longer for any given entry.

In concert the various adjustments work together to ensure that each car can compete equally while not completely removing the inherent strengths and weaknesses in each model.

The finishing order of the 2018 race was proof that the system works effectively, with three different brands – Audi, Mercedes-AMG and Porsche – filling the podium.

In 2019 the Audi will be required to race at 1275kg, 50kg heavier than its homologated weight of 1225kg.

R8’s will be required to run a pair of 39mm air restrictors, minimum ride heights of 65mm and 128mm (front / rear) and use a 30mm re-fueling-rig restrictor.

The Mercedes-AMG, meanwhile, runs at a heavier 1340kg at Bathurst with a pair of 36mm air restrictors attached to the front of it’s big V8.

However it can run a larger fuel rig restrictor – 33mm – and a lower rear ride height when compared to the Audi.

The Porsche is the lightest of the trio that finished on the podium last year, weighing in at 1245kg. It will run a pair of 41.5mm air restrictors and ride heights of 72mm and 124mm on the front and rear, respectively.

2019 will see one new and several updated cars tackle Mount Panorama for the first time.

The Generation II Bentley Continental GT3 will make it’s Australian debut while Asian-based outfit KCMG will run a pair of 2018-specification Nissan GT-R NISMO GT3s, meaning both will run to different BoP restrictions than the existing cars we’ve seen at Bathurst representing those brands.

The unique nature of Mount Panorama’s 6.213km layout has traditionally proved an impressive advert for the BoP system.

The combination of long straights, steep inclines, high speed sections and slower, more technical corners allows for a majority of competing models to utilise their relative strengths throughout each lap.

For instance, the Mercedes-AMG and Bentley entries have traditionally been strong climbing the hill, thanks to their larger capacity engines with more torque.

The Audi R8, meanwhile, is famed for being remarkable across the top of Mount Panorama where it can use it’s downforce and balance to fly from the Cutting to the Elbow.

Last year the Porsche entries had comfortably the best fuel economy of the race while in the past Ferrari’s have been strong, consistent performers throughout much of the lap.

McLaren’s 650s is renowned for being ultra-quick but challenging to drive on the limit while getting the most out of BMWs M6 has also proved hard work – though both have had success at Bathurst.

Five different brands have filled the top five finishing positions in the race on two occasions (2015 and 2016), the 2015 race setting a record with seven brands represented in the top seven at the finish.

Four different cars have won the last four races while a different marque has been on pole position for the last five straight years.