Emblems of VW Golf VII car are pictured in a production line at the plant of German carmaker Volkswagen in Wolfsburg, February 25, 2013. REUTERS/Fabian Bimmer/File Photo

FRANKFURT (Reuters) - U.S. authorities have found three unapproved software programmes in 3.0 litre diesel engines made by Volkswagen's VOWG_p.DE Audi NSUG.DE unit, German weekly Bild am Sonntag reported, without saying where it had obtained the information.

The software allowed the turbocharged direct injection (TDI) engines used in Audi’s Q7, Porsche’s Cayenne and VW’s Touareg models to shut down emissions control systems after about 22 minutes, the paper said. Official methods to measure emissions usually last about 20 minutes, it added.

Volkswagen has admitted it cheated on U.S. diesel emissions tests for years and said in June it would spend as much as $15.3 billion (£11.71 billion) buying back vehicles from consumers and providing funding that could benefit makers of cleaner technologies.

That settlement however would not address about 85,000 larger 3.0 litre Audi, Porsche and VW vehicles that emitted less pollution than 2.0 litre vehicles but were also fitted with illegal emissions-control equipment. Audi and Volkswagen notified U.S. authorities about these vehicles last year. A deal covering the 3.0 litre vehicles may still be months away.

Audi managers are scheduled to appear at a hearing in front of U.S. environmental authorities on Aug. 10, Bild am Sonntag said, adding the carmaker was bracing for a substantial penalty payment.

A spokesman for Audi declined to comment, only saying that talks with U.S. authorities continued and were aimed at a technical solution for the problem.

A spokeswoman for the U.S. Environmental Protection Agency declined to comment.

Volkswagen’s “Dieselgate” scandal had hurt its business and reputation and already cost it billions of dollars. It still faces criminal charges and law suits in numerous countries.