As Svizzero explains in the video, he hadn't planned for his 2008 BMW to become so thoroughly modified. But he says that he started driving it at the track more frequently, and he moved from basic upgrades to something wilder, which is where the V8 comes in. It's actually the second one to dwell in the car. To do the original swap, Svizzero bought a wrecked E92 M3 from England for the 4.0-liter engine. In fact, the M3's transmission, differential, and axles all migrated to the little 1 Series, too. Now, though, the 135i has a stronger V8. It's still M3-based, but has been stroked to 4.6-liters using a Dinan kit. The result is an impressive 502 horsepower at the crankshaft. It has an incredible sound that the video spends plenty of time showing.
Svizzero has made other changes, too. The body is modified to look like the 1M, complete with wider fenders, different front bumper, and 1M fender vents. The sunroof was also deleted and the roof panel replaced a carbon-fiber piece. The brakes are upgraded, and the interior now features a roll cage and race seats. However, Svizzero made sure the car was well-finished with fully functional factory air conditioning and stereo.
This actually isn't the first time we've seen this car, either. A couple years ago, it was featured on an episode of /Tuned, which has some extra information on the technical aspects of the build. But if you're looking to hear more about Svizzero and his car's story, and Leno's enjoyable commentary, check out the video above.