BMW 1 Series ECU Remapping & Engine Tuning

Which 1 Series engines gain the most?

The two 1 Series generations respond very differently, and induction is the reason. Most E8x petrol engines are naturally aspirated: the N45, N43 and N46 four-cylinders, and the N52 3.0 straight-six in the 125i, 128i and 130i. With no boost pressure to raise, most of them gain 15 bhp or less. The 2007–2011 120i goes from 170 to 185 bhp (+8%), and the 2005–2009 130i from 265 to 280 bhp (+5%). The 135i’s N54 twin-turbo six adds the most of any E8x petrol, going from 306 to 351 bhp (+14%), with torque rising from 400 to 465 Nm.

The E8x diesels are all turbocharged and gain more than most of the petrols sold alongside them. The 123d uses a twin-turbo version of the N47 2.0 four-cylinder and goes from 204 to 254 bhp (+24%).

Every F20/F21 engine is turbocharged, so the petrols gain far more than their E8x predecessors. The 118i shows this with both of its engines: the 2011–2015 car’s N13 1.6 turbo goes from 168 to 214 bhp (+27%), and the B38 1.5 three-cylinder that replaced it goes from 134 to 176 bhp (+31%). Against a 15 bhp gain for the naturally aspirated 2007–2009 118i, both add more than 40 bhp.

1 Series generations we cover

E81/E82/E87/E88 (2004–2013). The E87 five-door hatchback arrived in 2004 and was joined in 2007 by the E81 three-door hatchback, the E82 coupé and the E88 convertible. The 135i moved from the twin-turbo N54 to the N55, a single twin-scroll turbo six, in 2010, and the diesels switched from the M47 to the N47 2.0 in 2007.

F20/F21 (2011–2019). The F20 five-door and F21 three-door hatchbacks were built from September 2011 to May 2019. The N13 1.6 gave way to the B38 1.5 three-cylinder in 2015, the M135i’s N55 was replaced by the B58 in the M140i, and the diesels changed from the N47 to the B47 2.0, with the 125d using twin turbochargers throughout.

Last updated 19 October 2026