Porsche investigated over new emissions cheat

Germany's federal motor vehicle authority (KBA) has confirmed it is investigating Porsche over allegations it illegally manipulated its petrol engines to improve their emissions.

Reigniting echoes of the Dieselgate emissions scandal that engulfed its parent company, the Volkswagen Group, the KBA has confirmed the engines suspected of being fitted with illegal emissions software were fitted to Porsche 911 and Panamera models made between 2008 and 2013.

The charge that Porsche will have to defend itself over is that illicit countermeasures were secretly introduced to both the sedan's and sports car's software, allowing them to produce significant less NOx emissions during testing.

In a statement to Germany’s Handelsblatt newspaper, Porsche confirmed that its internal investigation into possible illegal engine software and hardware changes “found a few indications of possible misconduct”.

According to the VW-owned brand, Porsche alerted both German prosecutors and US authorities in "early summer".

It's not known whether Porsche's act of atonement kicked off the KBA investigation, or if the investigation had begun much earlier.

Porsche is not the only Volkswagen Group brand facing a renewed investigation into emissions cheating.

Audi has also been dragged into German courts over recent claims the turbocharged 2.0-litre four-cylinder petrol engine in the popular Audi Q5 employed a steering wheel sensor to trigger a switching off of the selective catalytic filter when the system thought it was being tested on a laboratory-style rolling road.

The system, prosecutors claim, sees the Audi Q5 2.0 TFSI produce 24.5 per cent higher NOx emissions in real-world conditions compared to when the sensor automatically switches off the exhaust gas filter.

Audi has already been caught manipulating emissions via an identical trick with its diesel engines.

It's not yet known whether Porsche used similar underhanded tactics to cheat emissions tests, but it's not the first time the car-maker has been embroiled in its own emissions scandal.

German prosecutors fined Porsche €535 million ($A880m) last year for lapses that allowed the company to cheat diesel emissions tests.

Separately, Mercedes-Benz parent company Daimler two weeks ago reached a $US1.5 billion settlement with North American authorities over a similar diesel emissions cheating scandal.