"Using the wildly popular Silvia S15 chassis as a starting point, Top Secret turned this car into a championship winning drift car. The modification list is nearly endless, but some highlights include: Top Secret intake/exhaust systems, Top Secret drift dampers, HKS GT30 Pro turbo, HKS 5-speed transmission, Cusco differential, Volk rims and Brembo brakes. Piloted by Ryuji Miki, the Top Secret Silvia collected a record 110pts and won the 2004 D1GP Championship. Don't let the drift pedigree fool you, this Silvia has lapped the Tsukuba circuit in a very respectable 1 minute flat."—Official description
The 2000 Nissan Top Secret Silvia D1-Spec - abbreviated as Top Secret S15 - is a pre-tuned variant of the Nissan Silvia Spec-R featured in Forza Motorsport 2, Forza Motorsport 3 and in Forza Motorsport 4 as a Unicorn car.
The Top Secret Silvia is a heavily modified S15 Silvia that competed in the Japanese D1 Grand Prix drifting series. It was prominently driven in the 2004 D1 Grand Prix season by Ryuji Miki, whom became the championship winner of the 2004 season.
The Top Secret Silvia was designed to offer strong drifting capabilities, which were achieved by combining a stripped out base with a near 50/50 weight balance with an extensively upgraded turbocharged engine that produces 534 hp and 380 lb/ft of torque.
The engine was built using an SR20 cylinder block with an HKS supplied enlargement kit and Tomei camshaft, along with an HKS turbocharger and a custom exhaust manifold. The fuel system was upgraded with 1000cc injectors and a second fuel supply line with an additional fuel pump. The cooling system was also overhauled to enable a V-mount intercooler setup.
- According to Forza Motorsport 4's benchmarking system, the Top Secret Silvia is capable of going from 60 to 100 mph in 3.6 seconds.