Each year, Continental Tires invites Europe’s top car tuners to southern Italy for its Nardo High Performance Event. The competition is simple: The team that sets the highest top speed wins. Modified Porsches have dominated the event, with other German brands usually filling up the rest of the leader board. This year, however, an American car is vying for overall honors—a Chevrolet Corvette Z06.

Munich, Germany’s Geiger Cars has been specializing in American vehicles since 1979. Though it imports new and used cars and sells many of them as-is, Geiger is best known for its modified machines—and it pulled out all the stops with the Corvette it brought to Nardo. The factory “Z06 505 HP” badges on its flanks no longer tell the truth: They are pessimistic to the tune of 385 horsepower. While the Geiger Z06 Bi-Turbo’s claimed 890 bhp is bested by the 1,000 ponies of the 9ff-modified Porsche 911 Turbo, the Corvette, with its lurid Kermit-green paint scheme, is definitely the most eye-catching machine present. Will it be the fastest?

Speaking to one of the Geiger mechanics, we learn that the Bi-Turbo did not start off as an official part of the Bavarian company’s Corvette tuning program. Instead, like the ZR1, it was envisioned and built by a couple of engineers in their spare time. When the conversion was finished, company boss Karl Geiger was so impressed with the car’s ballistic performance, he sanctioned its use for publicity work, including this Nardo shoot-out.

Not surprisingly, the biggest changes to the car were made in the engine compartment. The stock Z06’s hand-built 7,001-cc LS7 V8 is already a heavily tuned version of the standard V8, with forged titanium connecting rods, titanium inlet valves and sodium-cooled exhaust valves. These racy components allow this big engine to rev to 7,000 rpm, yet the V8 produces a reliable 505 bhp all day long.

When the factory came up with the idea of using a supercharger on the Corvette ZR1, it decided that the LS7 block was not man enough for the job, and used the 6,162-cc LS3 as starting point instead. This variant of the legendary small-block V8 has thicker cylinder walls to better withstand the higher combustion pressures of forced aspiration.

The Geiger engineers, on the other hand, were not only confident the LS7’s cylinder walls could handle a blower, they felt they could be even thinner, and proceeded to bore out the V8 to a monstrous 7.6 liters. In the process, they fitted lightweight forged pistons, titanium valve springs and a more aggressive camshaft. Only then did they strap a pair of turbochargers to custom-made exhaust manifolds and fit a substantial intercooler down low in the nose.