Audi’s expanding its customer car portfolio for aspiring racers.The company’s latest race car development is a GT4 regulation TT RS. Keen to offer racers a relatively affordable competition car option, the TT GT4 is trimmed out by Ingolstadt’s racing engineers with all the required durability and safety features.The cabin architecture is strengthened with a full-roll cage, whilst a puncture-proof fuel tank ensures low combustion risk even in the event of a severe impact. Lots of stock partsMany series production parts were carried over from the TT RS road car to its GT4 racing sibling in order to keep costs low. In fact, the TT GT4’s aprons and rear wing are all stock TT RS bits. Only the composite reinforced plastic bonnet, boot and windows are new surface panels. Powering the TT GT4 is Audi’s new five-cylinder 2.5-litre TFSI engine, producing 250kW and driving all four-wheels via an S-tronic dual-clutch transmission featuring an active differential lock to optimise traction. Audi’s TT GT4 is based on the (slightly) more hardcore SP4T car, prepared by siblings Martin and Nicolas Raeder.Keen to establish a strong presence in the burgeoning Asian racing market, Audi revealed the latest incarnation of its TT GT4 prototype at Shanghai street circuit over the weekend. The Raeder SP4T car was present too. Audi plans to offer the TT GT4 to customers for R1.2m by the start of the 2012 racing season.The company’s R8 LMS customer racing program has proven to be a huge success, with more than 20 cars having been delivered to customers for the 2010 racing season.