* FIA adds mystery European race to 2013 calendar
* German Grand Prix brought forward a week
* Plans for silent pitlane shelved (Adds detail, background)
By Alan Baldwin
LONDON, Dec 5 Formula One could have 20 races again next season after the governing FIA pencilled in a mystery European round in July to fill a space left by the postponed Grand Prix of America in New Jersey.
The International Automobile Federation said on Wednesday that the German Grand Prix would switch from July 14 to July 7 with July 21 now "reserved for another F1 European event" subject to approval of national bodies.
While no further details were given, speculation focused mainly on the possible return of the Turkish Grand Prix in Istanbul.
Germany's revised date would see that race follow on immediately from the British Grand Prix at Silverstone on June 30, according to the previous provisional calendar, while the new event would be back-to-back with Hungary on July 28.
Istanbul, where the FIA is currently holding its annual assembly and World Motor Sports Council meeting, would be a popular option for teams and drivers who rated the track on the Asian side highly before it was dropped from this year's calendar.
Formula One's commercial supremo Bernie Ecclestone dropped a hint on Tuesday when he told Italy's Gazzetta dello Sport that he was going to Istanbul "to try and revive the Turkish Grand Prix and take part in the world council."
France, which has been seeking a return with either its central Magny-Cours circuit or Le Castellet in the south, might be another possibility although that trail appears to have gone cold in recent weeks.
Another option could be Austria, whose former Oesterreichring (also known as the A1 Ring) has now been revamped by owners Red Bull since it last hosted a grand prix in 2003 and is an easy drive from Budapest.
Helmut Marko, a close aid to Red Bull's billionaire owner Dietrich Mateschitz, was quoted in Austria this week as saying a grand prix in the country could not be ruled out: "With Mateschitz, you can never say never. Let's see how it develops."
Red Bull have won the drivers' and constructors' championships for the past three years and Mateschitz is close to Ecclestone.
Formula One had a record 20 races this season but the absence of New Jersey, which had been due to make its debut with a race on June 16 while the debt-stricken Spanish city of Valencia dropped off the list, had reduced that to 19.
The FIA also made amendments to the technical and sporting regulations for next season.
They included more stringent front wing deflection tests, after a number of controversies in that area this year, and an increase in the minimum weight of cars to compensate for heavier Pirelli tyres.
The current 'force majeure' allowance, that can be used when a car stops on track in qualifying, was deleted and the FIA will instead determine how much fuel the car would have used to get back to the pits and add it to the one litre sample minimum.
Red Bull's world champion Sebastian Vettel was sent to the back of the grid in Abu Dhabi this season when he was told to stop his car on track after qualifying third.
The car was subsequently found to have not enough fuel on board to pass post-qualifying tests, although Red Bull were convinced the car had more in the tank.
The DRS drag reduction system can only be used in practice in the same zones where it will be available in the race.
On the sporting side, a 'curfew', designed to ensure hard-pressed mechanics and team personnel do not work around the clock at circuits, will be extended from six hours to eight hours on Thursday nights with only two exceptions allowed during a season instead of the current four.
Changes were also made to the 2014 technical regulations to reduce the costs of introducing a new engine, including postponing to 2017 a requirement for cars to be driven exclusively under electric power in the pitlane. (Reporting by Alan Baldwin, editing by John Mehaffey and Ken Ferris)