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Marshall Pruett | December 21, 2018 2:02 PM 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.
DPi
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.
Image by Levitt/LAT
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.
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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.
Image by Dole/LAT
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.