Could this be BMW's S58 twin-turbo inline-six?
Rumour has it that Toyota is hot-shoeing a more powerful engine into the Supra. Reports about using the S58 BMW M3 engine circulated as early as July of this year, with sources saying that the information came from an insider scoop. BMW M division president Markus Flasch didn't deny the possibility, but he didn't confirm it either, saying that it's unlikely.
Those early reports should be taken lightly, but this spy video from Youtube's statesidesupercars claims to have spotted a black Supra testing a different engine.
The speculation came from the observation that the engine sounded differently in the video, which we embedded on top. We think the difference is marginal, and there are many possibilities for this such as various aftermarket upgrades.
Then again, the speculation supports the aforementioned earlier reports. The BMW M3's S58 is the likely candidate to be used by the Supra GRMN, its alleged name, giving it a very potent 503 bhp (375 kilowatts) and 479 pound-feet (650 Newton-metres) of torque. These numbers will be sent to the rear wheels via BMW's seven-speed DCT.
The rumour is an interesting proposition, but we must take into account that BMW isn't keen on lending its M-infused engines to other automakers. The last time this happened was with the McLaren F1, which utilised a BMW S70 V12 power plant. As we've mentioned, it's unlikely but not impossible.
Again, take these speculations with a healthy dash of salt as nothing's confirmed at this point.