FRANKFURT -- Tesla's attempts to humble Porsche with a new lap record on Germany's legendary Nordschleife racetrack have reignited a controversy about the value of lap times, as the circuit steps in to quash claims of cheating.
Porsche and Tesla are battling to establish supremacy in lap times for four-door electric sports cars, but comparisons are not exact, as conditions, ranging from car modifications to tire types, vary with each test.
"We want to have circumstances that can be understood and replicated," said Nuerburgring spokesman Alexander Gerhard, adding that the racing circuit operator had moved to tighten rules by which an automaker can claim a certified lap time.
Setting a new record time for four-door electric cars would give Tesla's aging Model S a boost just as German rivals Audi, Mercedes-Benz, BMW and Porsche prepare to launch their own EVs.
Automakers use the Nordschleife, one of the world's most treacherous courses with 40 right-hand and 33 left-hand turns, to hone a vehicle's sporting characteristics and burnish a car's image for marketing purposes.
Tesla was spotted this week with a variant of its Model S sedan at the circuit, which is 12.9 miles long, with slanted cambers and a 984-foot altitude difference between its highest and lowest points.
German car magazine Auto Motor und Sport said a Tesla was seen recording an unofficial time of 7 minutes and 23 seconds, which would beat a lap time set by Porsche's Taycan, which Porsche says achieved a lap time of 7 minutes and 42 seconds.
But Tesla's challenge has prompted questions about whether the Silicon Valley automaker is playing fair.
"The car was heavily modified," said Stefan Baldauf, who photographs prototype vehicles being tested on the circuit for a living.
"Aside from a roll cage and the driver's seat, the interior had been stripped out," he added. "The windows were blacked out, so it was hard to tell."
The Tesla also appeared to have semi-slick tires, used only on racing circuits and unsuited for everyday use, Baldauf said.
A Porsche spokeswoman told Reuters its Taycan was tested using standard tires.
"A comparison is hardly fair if this is the vehicle used to demonstrate that Tesla is faster," Baldauf added.