The BMW M4/M3 uses the S55B30 engine.  The engine uses two mono-scroll turbochargers with a peak boost pressure of 18psi. The power is rated at 425 bhp while torque will be 550nm.

At GCAP Performance we have a few hardware and software modifications to help boost the power on your M3/M4.


We can offer a variety of exhaust systems for the M3/M4. 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 M3/M4. 


Carbon-fibre/ Matt black/ Polished tailpipes give an added look to the rear of the M3/M4, to display its sporting potential.


The most efficient way off adding bhp to your M3/M4 is a set of downpipes. By adding some decat downpipes you allow the turbo to spool quicker by removing the restriction in place after the manifolds

Charge Cooler

We use a CSF to upgrade the turbo cooling on the M3/M4.

Multiple air dividers cast into both the hot/cold side endtanks for optimized air flow through the custom designed CSF liquid-to-air intercooler core (CFD analysis and testing completed to ensure optimal performance)


With a 60% increase in core size compared to the OEM cooler this sytem ensure cool running temps.


Left/right, cross-flow, dual-pass core configuration with 2-stage water cooling for maximum efficiency and intake temperature reduction (vs. OEM single-pass vertical-flow design)


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).



431bhp / 550nm is increased to 500bhp / 680nm



431bhp / 550nm is increased to 530bhp / 720nm



We have seen up to 700bhp 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 performance car.


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.

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GCAP Performance

6 Powis Mews

Notting Hill


W11 1JN