M240i (G42)

The B58 responds strongly to software, so a stage 1 remap is the most popular first change and gives a large step in performance on its own. Owners often add a metal charge pipe and an upgraded heat exchanger at the same time to protect against boost leaks and heat soak. A GPF-back exhaust for sound, uprated brake pads and paddle shifters complete a typical first round of upgrades.

The B58 in the M240i is known for having a lot in reserve. Stage 1 software on high-octane fuel typically lifts output well above 400PS, and stage 2 with supporting intake, cooling and sports-cat downpipe hardware goes further still. Figures depend on fuel, climate and the tuner. Beyond the standard turbo's limits, builds usually add uprated fuelling, ethanol blends and stronger internals.

They are not essential for a mild remap, but both are common supporting mods. Aluminium charge pipes are widely recommended on tuned B58s because the factory plastic pipes can split under higher boost. The B58 uses a water-to-air intercooler, so an upgraded heat exchanger such as CSF's improves cooling capacity and keeps power more consistent during repeated hard runs and track sessions.

The ZF-based eight-speed automatic is widely regarded as robust at stage 1 and stage 2 power levels on the B58, which is one reason the M240i is popular with tuners. A transmission calibration can sharpen shifts and raise torque limits, and some owners add an uprated cooler for track use. At very high outputs the gearbox needs more attention, so plan the drivetrain alongside the engine.

Many engine parts carry over, because the G42 M240i shares the B58 straight-six with the G20 M340i and G22 M440i. Charge pipes, heat exchangers, intakes and some fuelling and tuning parts are often common across these models. Exhausts, brakes, suspension and body parts are usually specific to the 2 Series. Check the fitment listed on each product, or save your car to My Garage to filter results.

In the UK, fitting aftermarket parts does not automatically cancel BMW's warranty, but a claim can be refused if a fault is linked to a modification. Remaps are often detectable even after the original software is restored, so engine and drivetrain claims are the main risk. Many owners wait until the warranty ends or accept the risk. Always tell your insurer about any modifications.