AUDI is marking 20 years of its TT sports car with a special edition model and upgrades across the range of roadsters and coupes.

The TT 20 years limited model will be restricted to 999 examples worldwide and order books will open in the autumn with first deliveries due later in the year.

With seats finished in fine moccasin brown Nappa leather and with contrasting stitching the interior of the 20 Years special edition harks back to the early cars with their ‘Baseball Leather' upholstery.

Special TT 20 years badges on the steering wheel and gear lever knob also mark the car out, as do stainless steel tailpipes in a specific design, matrix OLED rear lights and matt-finished Audi rings above the side sills.

The car will be available in coupe and roadster body styles with either Arrow grey or Nano grey paint finishes.

As well as the special model Audi is also making changes across the TT range to mark the milestone anniversary.

The 1.8-litre, 180ps TFSI engine which has powered lead-in models until now is replaced by a 2.0-litre TFSI with 197ps, and the existing 230ps 2.0 TFSI is boosted to 245ps.

All the latest petrol engines are equipped with a petrol particulate filter and in the TTS and TTS Black Edition models this has the effect of slightly reducing the power output to 306ps from 310ps.

Nevertheless, 0-62mph performance has fractionally improved in both coupe and roadster variants with their respective 4.5-second and 4.8-second sprint times being a tenth faster than previously.

In conjunction with the 197ps engine there's now a choice of a six-speed manual gearbox or a seven-speed S tronic dual clutch transmission while the 245ps model is available with either a manual gearbox and front-wheel-drive or with the Stronic transmission and the multi-plate clutch-based quattro all-wheel-drive system.

Both versions of the higher powered TTS feature quattro as standard.

Externally, all TT models get a new Singleframe radiator grille as well as larger side air inlets and new wheel option.

S line and Black Edition models have a new full-length front splitter flanked by vertical inlets, side sills with inserts and, at the rear, vertical air inlets with horizontal fins below the rear lights and a remodelled diffuser.

For the S line a new 19-inch wheel design freshens the profile and the Black Edition specification - which sits one rung above in the line up - also benefits from a wheel upgrade from the existing 19-inch to a new 20-inch design.

It is also set apart by the addition of the fixed rear spoiler previously reserved for the flagship TT RS as a replacement for the current speed-dependent active spoiler, which becomes a no-cost option.

Rounding off the exterior changes a new turbo blue paint finish has been reserved for S line and Black Edition models, while new colours of cosmos blue and pulse orange have also been added to the palette for the range as a whole.

Inside, there are a number of detail enhancements with Sport and S line versions receiving folding door mirrors and heated seats while the S line specification is also enhanced by the addition of even more supportive Super Sports Seats.

The upgrade to Black Edition now brings the addition of piano black inlays and a new chrome slate grey finish for selected interior elements.

Elsewhere there are changes to the virtual cockpit display which now includes information on torque, engine performance and a G-force meter while LED daytime running lamps, cruise control, rear parking sensors and the Audi drive select dynamic handling system are now standard.

LED headlamps are now fitted to all TTs from S line and above while the TTS and TTS Black Edition cars now have a technology pack that includes a hard-disc MMI navigation system with three years' subscription to online services and wireless phone charging.

Prices for the new range - and the TT 20 model - are expected to be announced in the next few weeks.