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.
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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