IMSA has released its Balance of Performance tables for the upcoming Roar Before The 24 test that will be used as a first step to shape its final BoP figures for the season-opening Rolex 24 At Daytona.
With the new separation of DPi and LMP2 models into individual classes, some of the BoP work completed by IMSA centers on creating distinct performance levels for the two categories.
Weight reductions across all four DPi brands have been made. Using the most recent race at Petit Le Mans as a reference for where the cars have been taken, Acura’s ARX-05 is down 10kg from 940 to 930, Cadillac’s DPi-V.R drops 20kg from 950 to 930, Mazda’s RT24-P is the same 905kg, and Nissan’s Onroak DPi loses 5kg from 940 to 935.
On the power front, Acura’s twin-turbo V6 engine will have a slight bump in boost from 5600rpms to its 7050rpm redline. Cadillac’s naturally-aspirated V8 will breathe more freely with an increase of 0.3mm to its dual air restrictors, bringing the total through-flow number to 31.9mm. A 100rpm hike in maximum RPM from 7500 to 7600 has also been made.
Mazda, with its small four-cylinder turbo powerplant, has seen its boost figures adjusted along with new RPM reference points that differ from Petit Le Mans. The most notable aspect of the adjustment comes in an increase from an 8600rpm redline in October to 9300rpms to start 2019. Boost figures, in general terms, have been nudged up or down by small margins to accommodate the 700rpm hike in revs.
Nearly identical to Acura’s boost increases, Nissan’s twin-turbo V6 has gained power from 5800rpms to its 7100rpm redline.
Maximum fuel capacity adjustments were also implemented ranging from losing two liters to gaining three liters for the four models, with those changes based on power increases or anticipated fuel economy, in order to equalize the lengths of a full-tank stint. A minimum refueling time of 30 seconds will be enforced.
Only the French Ligier JS P217 and ORECA 07 LMP2 models are expected for the Roar and Rolex 24, with ORECA holding the monopoly of entries through its customer. Despite the unlikely appearances of Dallara’s P217 and the Riley/Multimatic Mk. 30 LMP2s, IMSA has set a uniform minimum weight of 940kg for all cars, cut the maximum RPMs from Gibson’s spec V8 engine from 8750 to 8250, set the maximum fuel capacity at 70L, and refueling must take at least 34 seconds.
GT Le Mans
Using the same Petit Le Mans reference points, BMW’s 1220kg minimum weight for its M8 GTE and Corvette’s 1240kg for its C7.R are unchanged. Two models will gain weight as Ferrari’s 488 GTE goes from 1265kg to 1270, and the biggest leap lands with Ford’s GT, up 20kgs from 1265 to 1285. Porsche’s 911 RSR is the sole GTLM car to carve weight, cutting 25kgs from 1265 to 1240.
Corvette has lost some power with a decrease in airflow to its naturally-aspirated V8 as its Petit air restrictor total of 31.5mm has been narrowed to 30.6mm. The other naturally-aspirated engine, Porsche’s flat-6, is unchanged at 32.2mm.
Of the three turbocharged models, BMW’s twin-turbo V8 has gained boost from 5000rpms to its 7000rpm redline, Ferrari’s twin-turbo V8 has not been altered, and Ford’s twin-turbo V6 has lost boost from 5500 to its 7200rpm limit.
Similar to DPi, fuel capacity changes are relatively small, and each stop has a minimum time of 34 seconds.
Finally, with the same October benchmark in place, starting minimum weights for 2019 fluctuate a bit. Acura’s NSX GT3 is down 10kg from 1330 to 1320. Audi’s R8 LMS GT3 has grown by 20kgs from 1320 to 1340. BMW’s M6 GT3 hasn’t changed, but Ferrari’s 488 GT3 has gotten lighter with a 20kg decrease from 1345 to 1325. Lamborghini’s Huracan GT3 is up five kilos from 1300 to 1305, the Lexus RCF GT3 has gone in the opposite direction with 20kgs coming off to make its former 1380 a slimmer 1360. The Mercedes-AMG GT3 is downsizing by 15kgs from 1390 to 1375, and Porsche’s 911 GT3 R holds station at 1285kgs.
Power modifications start with Acura’s twin-turbo V6, which loses small amounts of mid-range boost to its 7500rpm peak. Of the two other forced-induction GTD cars, BMW’s twin-turbo V8 has not been touched with boost alterations, but Ferrari’s twin-turbo V8 is down some boost from 5500 to its 7500rpm redline.
Of the non-turbos, airflow has been improved for the Audis with a move from 39mm openings to 40. Lamborghini has lost 1mm in a decrease from 39 to 38, and Lexus has gained 1mm from 39 to 40. No changes have been levied for the 36.0mm assigned to Mercedes-AMG or Porsche and its 43mm restrictors. As well, no changes to maximum RPMS for any of the GTD models have been outlined for the Roar.
In line with the other classes, small fuel capacity changes have been implemented and a minimum pit stop time of 40 seconds will be used.