What is it?
The decision to base the Audi A1 on the same PQ25 platform as the Volkswagen Polo’s is logical enough. Except that the PQ25 was engineered for front-wheel drive only. So Audi faced a dilemma for its more powerful A1s, including its high-performance S1.
Audi originally eyed doing the S1 with front-wheel drive. But after some thought about the ramifications to the image of its traditionally four-wheel-drive S-car line-up, that idea has been ditched in favour of a costly engineering programme to provide the PQ25 with four-wheel drive capability – the first fruits of which are driven here in the form of an early prototype fitted with the same driveline as the A1 1.4T range-topper.
What’s it like?
The mods to the A1’s existing structure are fairly straightforward. They include a propshaft running aft from the gearbox – a standard six-speed manual in our car – together with the adoption of an electronically controlled, hydraulically actuated multi-plate clutch. Along with an added pair of rear driveshafts, it all adds 90kg to the car’s weight.
The new clutch – basically the same unit used on four-wheel-drive A3s – continuously apportions drive between the front and rear wheels depending on prevailing traction, and it can send 100 per cent to either axle.