At the design stage Audi when to incredible lengths to optimise airflow, so why did they change the service flap on later cars?
Audi were very disappointed by the slow sales of the A2. What they thought would be a big hit was not a commercial success at all. There are various reasons for this, including the price and the fact that Audi didn't advertise the A2's aluminium body enough. Audi were also concerned that the A2's avant-garde aesthetics were part of the problem. So, without going to the expense of a full facelift, Audi decided to try to make the A2 look a little more 'normal' by just changing the service flap. The replacement 'fake slats' were supposed to make the A2 look like a bit more like every other car on the road at the time. I don't believe the change had any great effect on sales.
surely the earlier flap with its smooth shiny surface is much better than the later one where the grille must cause all sorts of turbulent air at the front of the car.
You'd imagine so, but it actually makes no difference. Cars like the A2, with a large, rounded front, don't actually 'path cut' through the air in front of them as you might imagine. Instead, they push along a static cushion of air that sits against the nose of the car. It is this static cushion of air that does the 'path cutting'. Consequently, there isn't much air flowing over the service flap, meaning the fake slats don't create drag.
...to be honest I prefer the look of the earlier smooth flap. ... but I'd love to here your opinions
I am 100% with you. The original smooth service flap is, to my mind, by far the nicer option. It's how the A2 was meant to be. The avant-garde, minimalist, ultra-modern, Bauhaus-esque appearance is, to my eye, greatly compromised by the 'fake slats' look. Although there are many beautiful A2s with the slatted front grille, they could all, in my opinion, be improved by being returned to the aesthetic that the designers originally intended.
Cheers,
Tom