The ULTIMATE Guide To Modifying Your S55 Powered F8X BMW (M3, M4, M2 C)

Since its release in 2015, the BMW F8X platform has quickly become an extremely popular platform for tuners, enthusiasts, runway racers, and just about everyone in between. Even in stock form, the BMW M3 and M4 is an extremely capable drivers car w/ 425hp inline-6 motor and a lightning quick 7 speed dual-clutch transmission (DCT).

But if you are here reading this article, chances are you are looking at ways to improve upon your F8X. Maybe you’d like a little more sound, faster acceleration, or improved handling. Whatever your goal is for your M3, M4, or M2 Competition, we are here to help educate you on all of the aftermarket options for your build! 

In this article we’ll go over options for:

Intake Kits
Tuning and Performance
Crank Hub Upgrade
Turbo Upgrades
Suspension and Handling
Exterior Mods


Intake Kits

Adding an intake kit to your S55 powered BMW not only increases performance and throttle response, but unlocks the addicting sound of your turbos spooling. 

There are a quite a few options for S55 intakes but there are 2 that stand out to us here at German Muscle. 

The CTS Turbo Intake Kit  provides a cost effective way to improve throttle response and unlock that glorious turbo spool sound from your S55. With a sleek matte black finish, the kit looks and fits right at home in your engine bay. Horsepower gains range from 9-12hp with this kit, but I’d say the main improvement is the sound. Sitting at $379.99, this intake is the absolute CHEAPEST mod that will make a night and day difference for your F8X. This was the first thing I purchased after I got my M4, and I’d recommend you do the same.

Looking to add some style on top of the increased performance and sound from your intakes? Check out the Eventuri V2 Carbon Fiber Intake System. This intake kit adds some sleek carbon fiber pieces to your engine bay and gives you something to show off when you pop the hood at car shows! Not only does it look good, it provides a closed intake system that prevents hot air from the engine bay getting into the intakes!

Horsepower gains with this kit are up to +20hp and +23tq, providing an easy increase in power with a simple bolt on-kit. 


The factory exhaust note of the S55 powered M cars is universally agreed on being one of the weak points of the platform. Paired with a good intake, the factory exhaust sounds pretty good on the inside of the car, but on the outside you get a raspy, tin-y exhaust note that definitely needs an upgrade.

Typically there are 3 options when choosing an exhaust for your M3, M4 or M2 competition: 

  • Mid-Pipe paired w/ Factory Muffler
  • Axle-Back system w/ Factory mid-section
  • Full Cat-Back exhaust system.

Regardless of which you choose, modifying your exhaust provides a significant improvement over the factory system. Here are some recommendations we have for each of the 3 types of exhaust setups.


The Active Autowerke Performance Mid-Pipe exhaust system is a cost-effective way to, not only improve upon the S55’s exhaust tone, but also improve overall performance. Active Autowerke specially designed this mid-pipe to eliminate the highly restrictive nature of the OEM F80 M3 and F82 M4 mid pipe – thus creating optimal exhaust flow and drastically improving performance.

There are 2 configurations of this mid-pipe. The single mid-pipe (which is shown above) and the Equal Length Mid-Pipe. Either of these configurations can be had with or without a resonator, I personally prefer the resonated versions of both mid-pipes, allowing for a smoother sound, especially you have (or are planning to add) aftermarket downpipes.

Check out each of them below!

Active Autowerke 2015-2020 BMW M3/M4 (F8X) Equal Length Mid Pipe
Active Autowerke 2015-2020 BMW M3/M4 (F8X) Resonated Equal Length Mid Pipe
Active Autowerke 2015-2020 BMW M3/M4 Performance Mid-Pipes

Axle-Back Systems

If you are looking for a more aggressive rear-section for your M3/M4 but aren’t looking to change out the mid-pipe, Active Autowerke also has a solution for you. Their 3-Can Valved Rear Section Exhaust was carefully engineered to eliminate the unflattering sound of the factory M3 and M4 exhaust, while also allowing for optimum flow and resonance. This system can be run with the factory exhaust or paired with one of Active Autowerke’s Mid-Pipes for maximum performance and sound!

Active Autowerke BMW 2015-2020 F8X M3/M4 Rear Exhaust Section – 3 Can Valved

Cat-Back Exhaust Systems

Mid-pipe this, axle-back that… do you just want a ‘one and done’ solution that will completely transform your car’s exhaust? Check out these options below.

Behold, the Valvetronic Designs Cat-Back Exhaust for the BMW M3 and M4. This is my ABSOLUTE favorite modification for this platform. It combines the equal length style mid-pipe with a valved rear section for (in my opinion) the best sounding full exhaust system on the market. Not only does it sound great, it’s extremely cost-effective, starting at $3299.99. More details below.
Valvetronic Designs 2015-2020 BMW M3/M4 (F8X- S55) Equal Length Valved Exhaust

Not sold on the Valvetronic Exhaust? Take a look at the full exhaust system that is offered by FI Exhaust.

Not only does it sound great, the FI Exhaust is extremely customizable, with different options for downpipes, exhaust, tips, and even the option to control the valves with your phone! Take look!

FI Exhaust 2015-2020 BMW M3/M4 (F80/F82) Valvetronic Cat-Back Exhaust System

Tuning and Performance

Now that we’ve gone over how to get your S55 sounding right, it’s time to make some power! When it comes to increasing performance on these cars, there a few key components that go into a well-sorted build.

Regardless of what modifications you make to the motor, tuning is your number one priority. You can throw all the “go-fast” parts in the world at your car; but without a solid tune it means nothing.

Our favorite tuning platform for the F8X platform is BootMod3 by ProTuningFreaks.

BootMod3 unlocks the full tuning capabilities of the S55, allowing you to build the ultimate tune and have the ability to go from stock to full race calibration; or anywhere in between. This is a must-have software for anyone looking to increase the performance of their M3 or M4. 

This also opens up the opportunity for alternative fuel such as E85. Switching to ethanol blend tune can drastically improve your performance, without having to add any additional modifications.

ProTuningFreaks even offers their own flex fuel kit to assist with this.
BootMod3 BMW N55/S55 Flex Fuel Kit

This is by far the most power per $ available to the F8X platform. With stock cars dyno-ing around 370-390whp a simple Stage 1 can increase that to 460-480whp (depending on supporting mods and dyno conditions). That’s almost a 100whp gain with just a tune!

Once you have your tuning platform chosen, the next place to go for some extra horsepower is the addition of a set of aftermarket downpipes. The factory downpipe and catalytic converters tend to be very restrictive, so switching to an aftermarket, free flowing design allows you to capture some serious horsepower gains, as well as some added sound!

CTS Turbo has us taken care of with their 3″ Downpipe for the M3/M4/M2 C.

Their downpipe is good for an extra 20hp and 22tq and can provide much more when combined with a tune!

Once you start throwing more power at your S55, its important to make sure you keep your motor and intake temperatures cool, and an upgraded heat exchanger will do just that. 

CTS Turbo’s Heat Exchanger Upgrade Kit is an easy, bolt-on, solution to keep your intake air temperatures down and your motor running strong. Cooler intake temps means denser air, which means more power!

One of the weak points of the S55 motor is the Top-Mount Intercooler. These can be found to leak on cars with higher miles, especially when modified. Luckily CTS makes a direct replacement that not only will fix a leaky stock unit, but will also perform much much better.

CTS Turbo 2015-2020 BMW M3/M4/M2 C Air-To-Water Intercooler Upgrade

It’s also recommended when running high boost levels to upgrade the factory charge pipes and J-Pipe as well! Both options are also offered by CTS Turbo as well!

CTS Turbo 2015-2020 BMW M3/M4/M2 C S55 Charge-Pipe Set
CTS Turbo 2015-2020 BMW M3/M4/M2 C J-Pipe Throttle Body Charge Pipe

To make things easy for you guys, we’ve even packaged up our favorite performance mods into easy “Staged” packages! We bundled up the most cost-effective modifications to get you the most horsepower for your dollar, all in one easy bundle!

Check out our Performance Packages Here!

The performance capability of the S55 is definitely the highlight of the F8X platform. With endless tuning options, your M3/M4/M2 C is blank canvas of tuning potential!

Crank Hub Upgrade

While upgrading your S55 to increase performance, it’s important to take preventive measures to ensure the motor is still safe and reliable.

If you’ve done any research on this platform I’m sure you’ve seen or heard of the mysterious “Crank Hub issue” that supposedly plagues all of the S55 motors in your cars. A great deal of motors that have been modified (as well as stock cars) have had their crank hub “spin”, resulting in total engine failure. 

What does this mean for you? If I were modifying my car at all (or you are out of the powertrain warranty on a stock car) I would suggest upgrading this weak point of the motor. With an engine replacement costing upwards of $20k, this preventive measure can provide the peace of mind of a safe, strong motor.

Turbo Upgrades

If all that talk of intakes, downpipes, and exhausts didn’t get you excited about your S55’s power potential, well this part just might. When it comes to making BIG power on this motor, upgrading your factory turbos will do the trick. 

The Pure Stage 2 and Stage 2+ turbo upgrade is available for the power hungry F8X owners. There are multiple builds utilizing these turbos that have seen power numbers OVER 700WHP! Just make sure you’ve already upgraded that crank hub! 

Suspension and Handling

So we’ve gone over the performance and tuning capabilities of the M3, M4, and M2 competition. But that’s not the only thing that’s great about the F8X. This platform handles quite amazingly from the factory, but that doesn’t mean it can’t be improved upon. 

Our recommendation for suspension upgrades is the KW V3 Coilover Kit

Not only does this kit give you the ability to lower your car and give it a much more aggressive look and feel, the KW’s are a significant improvement to factory suspension, giving you full control of rebound and compression dampening. 

Whether this your daily driver or a weekend warrior, the KW V3s are a must needed upgrade for both function and form.

Not trying to spend $3k on suspension and just want to lower the car a little bit? The KW HAS Kit is for you. While keeping the factory shocks and dampeners, this kit allows you to lower the car to your desired height with its adjustable springs, allowing you to dial in your fitment just right!

KW Suspension 2015-2020 BMW M3/M4 Height Adjustable Spring (HAS) Kit

Exterior Modifications

So we have your F8X dialed in, it’s sitting right, makes more power than you can imagine, but we’re missing one thing, style! There is an ENDLESS list of exterior modifications available for the F8X, which is a gift in itself, as it allows you to build your M3 or M4 in your own unique way. But instead of going over every imaginable option, I’m just going to quickly highlight my favorite exterior pieces that are available!

Front Lips

RW Carbon 2015-2020 BMW M3/M4 (F80/82/83) Performance Style 3-Carbon Fiber Lip Spoiler

RW Carbon 2015-2020 BMW M3/M4 (F80/82/83) Varis Style Carbon Fiber Front Lip

Side Skirts

RW Carbon 2015-2020 BMW M3 (F80) RWS Type I CF Side Skirt Extensions

RW Carbon 2015-2020 BMW M3 (F80) Carbon Fiber Side Skirt Extensions

Rear Diffusers

RW Carbon 2015-2020 BMW M3/M4 (F8X) Kholen Style Carbon Fiber Style Rear Diffuser

RW Carbon 2015-2020 BMW M3/M4 (F8X) Carbon Fiber Performance Style Diffuser

Rear Spoilers

RW Carbon 2012-2020 BMW 328i/30i/35i/40i/M3 (F30/80) GTX V2 Carbon Fiber Trunk Spoiler

RW Carbon 2015-2020 BMW M2/M3/M4 (F8X) DTM Style Carbon Fiber Rear Wing


BMS 2015-2020 BMW M3/M4/M2C (F8X) Straight Cut Billet Exhaust Tips (set of 4)

RW Carbon BMW 2012-2020 428i/435i/440i/M3/M4 Gloss Black Grilles

RW Carbon 2012-2020 BMW 3-Series/4 Series/M2/M3/M4 (F8X) Carbon Fiber Steering Wheel Replacement


Well, if you’ve made it this far, thank you so much for reading! If you made it this far and bought every single thing that I’ve listed, congratulations on building a BADASS F8X, if not, I’d consider adding a few of those items up top to your cart ;).

The F8X and S55 platform truly gives you the versatility to build the car however you want. From canyon carvers to half-mile warriors, the options are endless. The team at German Muscle is excited for the opportunity to be your partner in your build and we encourage you to reach out to a specialist with all of your F8X and S55 questions!


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