Nissan is gathering evidence in Tokyo before unleashing a rebuttal of Porsche's claims that its GT-R could not have achieved a claimed 7 minute 25 second lap at the Nurburgring as a stock-standard road car.
It has deliberately avoided commenting until it has everything ready to prove its point.
But Nissan was angered by Porsche's attack on its GT-R, which came after the German company ran a back-to-back comparison with its 911 GT2 and Turbo and could not get within 25 seconds of the Japanese lap record for a production car.
There were talks late last week at the Paris Motor Show as Nissan executives tried to negotiate a back-room compromise with Porsche, but these failed with the German company standing by its claims.
This forced Nissan to mount a major case with everything from independent video footage to the disputed Dunlop tyres used by former F1 driver Toshio Suzuki during his 7:25 run.
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