The online calculators for car acceleration show that for a 900kg car with 140bhp and RWD you could expect a 0-60 time of 6.5 seconds or so, so your 7.5 second real world time sound about right to me.
For me, the 0-60 time is pretty irrelevant. The 35 - 70 time, however, is much more interesting, as that's the range in which I do most of my overtaking.
If you have a smart phone, you could try one of the apps like Dynolicious / Log Box to get some data logging functionality.
