The BMW M140i [F20/F21] is a true modern classic in the hot hatch world. With its 3.0-litre turbocharged straight-six engine, rear-wheel drive layout, and everyday usability, it delivers an exhilarating blend of performance and practicality that few rivals can match. Packing 340PS out of the box, the M140i is quick — but with the right modifications, it can be transformed into something truly special.
At Demon Tweeks, the M140i is one of the most popular modern BMWs we see customers modifying. Thanks to its B58 engine, strong chassis and stealthy styling, it’s the ideal blank canvas for tuning — and with a huge range of upgrades available, you can dial in performance, handling, and looks exactly how you want it.
What Mods Are Best?
If you’re planning to upgrade your BMW M140i F20/F21, here are the Top 5 Mods we recommend:
- Body Kit
- Exhaust
- Induction Kit
- Coilovers
- Brakes
Each of these will enhance the look, feel and performance of your M140i, whether you’re building a daily street weapon or prepping it for serious track use.
Body Kit
Let’s be honest — the M140i is a bit of a sleeper. But that doesn’t mean it has to look anonymous. Adding a Maxton Design body kit not only sharpens the car’s styling, but also improves aero and downforce, especially at higher speeds.
Why Upgrade?
- More aggressive and sporty appearance
- Improved aerodynamic performance
- High-quality materials and perfect fitment
- Stand out from the crowd
Recommended Product:
Choose from front splitters, side skirts, rear diffusers and spoilers — all made from durable ABS plastic with precision fitment and aggressive design that complements the M140i’s performance credentials.
Exhaust
Upgrading your exhaust system is one of the best ways to bring your M140i to life. A performance stainless steel exhaust enhances sound, improves exhaust flow, and reduces back pressure — helping your B58 engine breathe more freely and make more power.
Whether you’re after a subtle improvement or full-on track-day noise, there’s a system for every build.
Why Upgrade?
- Sharper, deeper exhaust tone
- Improved gas flow = more power
- Stainless steel = longer life and better heat resistance
- Optional resonated/non-resonated and tip finishes
Recommended Product:
Available as cat-back, downpipe, or turbo-back systems, Milltek’s options give you the freedom to tailor your sound and performance. Multiple tip finishes and bore sizes available.
Induction Kit
The stock M140i airbox is good — but it’s built with noise suppression and emissions in mind. Upgrading to a performance induction kit gives the car a crisper throttle response, louder turbo induction sound, and the airflow needed to support future power upgrades.
Why Upgrade?
- Increased airflow for more power
- Improved throttle response and turbo spool
- Louder, more aggressive induction noise
- Perfect for use alongside tuning and remaps
Recommended Product:
- Pipercross Performance Induction Kit
This kit replaces the restrictive OEM airbox with a high-flow cotton or foam cone filter, improving performance and adding that addictive turbo hiss under acceleration.
Coilovers
While the M140i handles well out of the box, it’s still a road car at heart. Upgrading to a coilover suspension kit gives you full control over ride height, damping, and rebound – letting you fine-tune the chassis for fast road or track use.
Why Upgrade?
- Lower ride height for better looks and handling
- Reduced body roll and sharper response
- Adjustable damping and rebound on most kits
- Options for road, fast-road or track
Recommended Products:
Choose from:
- KW V1 – Pre-set damping, height adjustable
- KW V2/V3 – Adjustable damping for road and track
Whichever route you take, coilovers offer the biggest single improvement in handling, confidence and road feel.
Brakes
With 340PS and plenty of tuning potential, brake upgrades are essential on the M140i. Whether it’s for fast road driving or full-on track use, Probite brake kits deliver serious stopping power with improved bite and fade resistance.
Why Upgrade?
- Shorter stopping distances
- Improved high-temperature performance
- Less fade under hard braking
- Multiple pad compounds for road or track
Recommended Product:
Choose from:
- OE-style coated discs for daily drivers
- Dimpled and grooved discs with Black Diamond coating for enhanced cooling and style
- Pad options from fast-road to track-day compounds
Summary
The BMW M140i F20/F21 is one of the best all-round hot hatches on the market – but with a few carefully chosen mods, it can be transformed into something truly special. Whether it’s aggressive Maxton bodywork, a Milltek exhaust, a responsive Pipercross induction kit, KW coilovers for razor-sharp handling, or upgraded Probite brakes for serious stopping power — each mod adds to the experience of owning and driving a properly sorted M140i.
At Demon Tweeks, we’ve got everything you need to modify your M140i. Our expert team can help you choose the right upgrades for your build, and we also offer professional fitting at our Wrexham HQ to take care of everything from install to setup.
Ready to build your perfect M140i? Let’s make it happen.