I'll TRY:
1., 2. and 3. gear of the new model are shorter than the series I ones. If the cars had the same bhp figures the one with the shorter ratio would accelerate better. The car would feel more powerful.
The fifth (and the fourth) gear of the new cars is longer. It will accelerate not as good as the old version but mpg will be higher.
I'm sure someone will be able to explain this better.
