Considering UDMs hav various engine cc & types, if we want to hav only a few categories, perhaps we can group it by the max bhp:
A. Up to 199hp - TTA: 3.09
B. 200-249hp - TTA: 2.59
C. 250-299hp - TTA: 2.49
D. > 300hp - TTA: < 2.39
Those TTA r just indicative guestimates based on last mth's RS Trackday.