Right when you assumed every possible engine swap and conversion have already been done, Top Secret comes by and stuns everyone. While it's difficult to come up with unique, never before attempted projects, Top Secret's Nagata-san manages to do it year in and year out. Last year it was the VQ35DE powered BNR32 Skyline GT-R and before that it was the twin-turbo V-8 powered V35 Skyline 350GT. For 2007, they've gone one better - if that's even possible. Behold the Top Secret V-12 Supra!
In 2006, when thinking about his next Tokyo Auto Salon (TAS) project, the tricky part for Nagata-san, aka Smoky, was making sure this particular car would top all of his past creations. And, to make things even harder, his choice of base cars was sort of restricted, seeing as how slow Japanese manufacturers are handling the development of their next batch of high-performance sports cars. As such he resorted to a car he knows very well, the JZA80 Toyota Supra. The Supra's large-engine bay opens up a lot of possibilities when it comes to engine tuning and engine swaps, and Top Secret has done everything from a T88 powered, 2.2L, four-cylinder, 720ps 3S-GTE to a 1,000ps RB26. But Nagata-san wanted to go one better by doing something completely crazy on the engine front and nothing really beats shoehorning a V-12 into the engine mounts!
The only Japanese-produced V-12 engine, the 1GZ-FE from the Toyota Century, fitted the bill perfectly even if it wasn't very easy, or cheap, to source. Of course it didn't end there, after all this is Top Secret we're talking about. Smoky wanted to go all out so he threw two HKS GT-RS turbines into the equation in the pursuit of a little more performance, since Toyota's 4,996cc V-12 is somewhat lethargic with a maximum output of only 280 ps at 5,200 rpm. It isn't even too impressive on the torque side of things, with only 46.9kgm developed at 4,000 rpm. So with the engine in hand the work began with laying out the twin-turbo system and the endless modifications required on engine swaps of this nature.
With considerable time constraints to get the car ready for TAS, Smoky decided to keep the 1GZ in standard tune and see what could be achieved by force-feeding it a low amount of boost. The engine was mounted as low as possible in order to allow enough space for the custom inlet plenums to be fitted on top of the two banks. This created a few problems with the sump, which had to be scrapped. So Top Secret swapped a very thin custom aluminum sump, which ended up considerably cutting the sump's oil capacity. To fix this problem, Top Secret created a one-off semi-dry sump setup. Ogura Clutch helped by building an external oil pump which was mounted low-down and belt-driven directly from the crank pulley. Large diameter oil lines help to distribute the oil where needed, keeping the engine's internals nice and happy.
Then, a set of exhaust manifolds were made to fit the GT-RS turbines. From this point on it became a bit of a piping nightmare, but the result is nothing short of exceptional. Once the compressed charge leaves the front-mounted intercoolers it's fed to opposite banks of six-cylinders via custom manifolds. The electrical throttle system of the stock 1GZ was dropped in favor of two N15 Pulsar mechanical throttles. In typical Top Secret style everything, including the engine covers, was polished to a mirror finish.
Even if the engine was positioned as far back as possible there's still a hefty weight hanging over the front end so they decided to shift the radiator all the way to the back of the car. Bespoke piping was laid underneath to take the hot coolant to the radiator, while a return pipe takes it right back into the engine. Two oil coolers were thrown in for good measure and positioned in a V-mount layout with the intercoolers. With a few modifications, the stock JZA80 six-speed Getrag transmission was fitted and mated to an ORC twin-plate clutch.