9ff's 910hp Porsche 911 Turbo TRC 91

Porsche specialist 9ff has dropped its potent 4.0L biturbo flat-six into the Porsche 911 Turbo Cabrio, and in doing so has created the world’s fastest convertible. Developing 780hp in the Cabrio, the modded 911 drop-top can reach a top speed of 381km/h.

Reserved for the coupe is a more powerful version of the same engine, which develops 910hp and 910Nm of torque. With this level of output, it takes just 3.1 seconds to reach 100km/h from rest all the way to a top speed of 392km/h thanks to the dual-clutch gearbox specifically designed for it.

To achieve this level of performance, engineers took the standard 3.6L biturbo motor from the regular 911 Turbo and added their own custom turbochargers, a sports air-filter, larger injectors, modified cylinder heads and a stainless steel exhaust system with special manifolds as well as high-performance catalysts, and finally, an extensive increase in engine displacement to the tune of 4.0L. To make sure everything is in check, all the modifications are controlled by means of a reprogrammed ECU.

Externally, the cars get a modified racing front grill for improved airflow, a boot lid made of carbon, a custom aero package, 20in wheels and a more powerful braking system. Click ahead for our complete gallery.