At least this sounds like an honest mistake.
Over the past two years or so, automakers across the board have been caught fudging emissions data. Subaru admitted to falsifying emissions data last year in 2018 and Nissan followed suit just a few months later. Mazda also admitted some of its tests were conducted under improper conditions and it looks like the Japanese automaker wasn't the only one.
Reuters reports that Porsche has recently alerted the German authorities to potential issues with its emissions data for the 911. At least Porsche was quick to address the issue instead of waiting for it to become a scandal.
The German automaker alerted authorities following a report in Der Spiegel magazine. "Porsche has identified issues in connection with individual roll-out tests," the company said in a statement, affecting several 2016 and 2017 911 models. These issues involve inaccuracies with the car's wind resistance values and corresponding information, which lead to differences in observed fuel economy and emissions.
Since the 911 can possess drastically different aerodynamic depending on the model, we aren't sure which models are impacted specifically. For example, the GT3 has a big rear wing, which creates far more aerodynamic drag than a base Carrera. Porsche reportedly failed to factor in the correct drag coefficient, which led to the inaccurate fuel economy data.
"The company is continuing its internal investigations in close consultation with the authorities," Porsche said, confirming that the issue has nothing to do with engine software. German law stipulates an automaker can be fined if emissions and fuel economy vary by more than 10% from their claimed values. If Porsche's estimates are off by more than 10%, the company may be required to offer owners compensation. There is still no word of how much Porsche's numbers are off or how much compensation would need to be paid out.