the engine physics of this new TDU suck really badly. take the viper for instance, in TDU1 the viper would pull hard from 2000rpm upwards with some serious torque. in TDU2 you got to rev the viper like a civic type R just to make it shift.
same with the vw toureg, 5ltr v10 diesel with like 550ftlb torque at 2000rpm, it dont move at 2000 rpm, you need to take it right up to 4500rpm to make it get anywhere.
when it comes to simulating the engine torque curves the original game was considerably better, and is in my opinion still the best game at simulating engine power/torque delivery. in TDU1 you can actually feel when the turbo charger has kicked in in cars that have a turbo, e.g the xj220, lotus exiege etc etc.
TDU2 = crap in my opinion.