
With 20 cars from 10 teams now in the starting line-up, organisers have decided that five cars instead of six will be eliminated at the end of each of the first two parts of qualifying.
The rules come into force for Saturday's qualifying for Sunday's Turkish Grand Prix in Istanbul.
With only 20 cars racing, five rather than six cars will be excluded after each of the first two parts of qualifying.
Ten cars will still race for pole position in the final 10-minute phase.
The Super Aguri team - which had no points from four races this season - pulled out of F1 on Tuesday because of a lack of funding.