The M140i/240i/330i/440i X3 M40i are powered by the B58 engine. The BMW B58 is a turbocharged inline-six engine which began production in 2015. Compared with its BMW N55 predecessor, the B58 features a 20% increase in boost pressure, a closed-deck engine block design, an increase in compression ratio to 11.0:1 and a slight increase in displacement from 2,979 to 2,998 cc. The intercooler - a water-to-air design - is integrated into the intake plenum, to reduce the volume of air between the turbocharger and the cylinders

At GCAP we have designed a package to further refine the German sports car's character with a few simple modifications.


We can offer a variety of exhaust systems for the 40i engines. We recommend brands such as Remus, Milltek, Scorpion and Akrapovič. 

A simple plug-and-play system offers a superb addition to improve the performance of the BMW B58 engines.


By fitting a decat downpipe, you can instantly unlock huge amounts of power plus added crackles on the overrun in sport and sport plus mode. Full systems are advices for big power and hybrid turbo installs.


By replacing the factory air filter element with a high flow performance filter from the likes of Pipercross, allows the car to breath better, particularly when tuning. The high flow filter is washable (so can be refreshed with a service) and carries no extra noise.

To further increase performance, we recommend a full induction system with a cone filter and a larger bore inlet pipe. Such brands as Eventuri and BMS offer fantastic looking induction kits which boost performance even further. 


We have developed our own software to increase the cars performance. This comes in two forms. A stage 1 map (I.E. a software only calibration with no hardware changes) and a stage 2 (with our turbo back exhaust system).



335bhp / 369lbft is increased to 435bhp / 425lbft



335bhp / 369lbft is increased to 450bhp / 440lbft



We have seen up to 550bhp with the use of hybrid turbos (please contact for more info).

When tuning we measure afr, ignition timing, intake temps, EGTs etc. to ensure our tune is as safe and reliable as possible whilst drawing the most out of your supercar.


As with most BMWs, the brake system is excellent. However we can offer modified braided brakes lines. Our lines have a stronger wall density delivering a more precise and accurate brake pedal feel. This translates into more confidence in your sports car.