The contest for the Porsche Carrera Cup GB will only be decided in the final two races of the season as Tim Harvey and Richard Westbrook go head to head at Donington Park over the weekend of 25/26 September.At the end of Sunday afternoon, one of them will be crowned champion after a tremendous season-long battle and they will go to Donington Park competing not just for the prestige of winning the coveted title. The overall champion will take away the keys to a brand new Porsche Carrera road car; it's a £55,000 prize and is one of the biggest awards in British motor racing.In truth, there has been little to choose between Harvey (Team RPM) and Westbrook (Red Line Racing) this season. Harvey has won eight times in 18 races while Westbrook has taken six wins. Frequently they have raced wheel to wheel in some mighty contests and they now head for Donington just five points apart. Harvey holds the advantage, but with a maximum possible score of 43 points available across the two races, it is too close to call.Importantly, there is an extra point for pole position and a point for fastest lap in each race. However, Westbrook knows that he has to beat Harvey to negate that five-point margin. “It’s going down to the wire, and that’s how it should be!” reckons Harvey, who will again dovetail his Porsche races with live TV commentary work on the BTCC races. "It's wide open for Donington," adds Westbrook, who spent much of the season playing catch-up after a non-finish in round three at Brands Hatch.The outcome is likely to be in doubt until the final laps of the second race, but what is certain is that it will be a high-pressure weekend for both drivers and their teams.However, this is far from a two-horse race as, although their overall title hopes are gone, at least three more drivers are firmly in contention for race wins. Jason Templeman (Team VLR) was supreme at Brands last month and will be aiming to fend off Irish charger Jonathan Fildes (TCR) in the battle for third place. Templeman had a modest weekend last time out at Snetterton, but will be determined to be back challenging for race wins at his home track. Meanwhile, Damien Faulkner (Motorbase Performance) has been on the podium five times since joining the championship in June and is quite capable of victory.Nigel Rice (Red Line Racing) and Andy Britnell (Motorbase Performance) head the next pack, while Jason Young (Red Line Racing) and Gary Britnell (Motorbase Performance) are heading for top 10 finishes in the championship. A gaggle of other quick racers should pack the field, including David Pinkney, Marcus Thomas, Martin Rich and Mark Hazell. The battle for the overall drivers' crown is not the only contest at Donington. The prestigious teams' championship is also being contested and although Red Line Racing clinched the crown at Snetterton, the battle for second and third places is wide open. Team RPM, Motorbase Performance, Team VLR and Team Parker Racing are all in the hunt, so every point is going to be hotly contested.Provisional championship positions after round 18:1 Harvey 312; 2 Westbrook 307; 3 Templeman 220; 4 Fildes 212; 5 Rice 184; 6 Andy Britnell 164; 7 Young 119; 8 Gary Britnell 105; 9 Faulkner 100; 10 Marcus Thomas 86; etc.