The 1.6 liter common rail direct injection petrol engine makes more power via a larger twin-scroll turbocharger, a performance air filter, air mass meter, exhaust system, catalyst, and an uprated turbocharger inlet manifold diameter. These JCW engines are built at BMW's Hams Hall plant and have been strengthened with reinforced polished pistons, a strengthened cylinder head, and a modified cylinder gasket. Intake valves and valve seat rings have also been upgraded with stronger materials.

The engine's compression ratio has been reduced to make up for the larger turbocharger boost, which now maxes out at 1.3 bar instead of the standard "S" engine's 0.9 bar. Peak torque of 260Nm kicks in at 1,850rpm thanks to the fast spooling twin scroll design of the turbocharger, despite it being larger than the standard size. The 6-speed manual gearbox has been strengthened to take the additional power and torque.