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  • Writer's pictureMMR Performance

Building the ultimate BMW F82 M4. What are the best modifications?

The brief was simple - build the ultimate MMR F82 BMW M4 which can be used for road use and occasional track days, whilst exploring what products make a performance difference to the tail-happy drift machine.


How much horsepower does an f82 M4 make? How can I make my M4 faster? How much does it cost to tune an M4? These are questions we're here to answer.


BMW M4 F82 on the road

Let's start with the car, with so many options to choose from under the BMW umbrella - FWD, RWD, XDrive, saloon, hatch, 6cyl, 4cyl, enormous grills... we wanted to choose something that would welcome our products, but also something we wouldn't be afraid to push to the limit.


We wanted to build the ultimate F-Series BMW, whilst exploring different performance modifications to see what benefits the car and what hinders it. But that wasn't where this build was heading, no sir - we wanted to dive deep into the F82 chassis to see what makes these cars tick. Should you replace the crank hub? Does an uprated charge cooler perform better than OE? Does a panel filter add power?


Choosing the car for a build.


We opted for RWD of course! A standard 2015 plate, DCT, low mileage example finished in Black Sapphire Metallic with matching black leather - perhaps a little vanilla, but a great starting point.


The first-gen F82 M4 houses the S55B30 twin-turbo inline-six engine, producing 425 BHP & 406 LBFT from the factory. We opted for the 7-speed M-DCT transmission, accelerating the 1612kg M4 to 0-62 in 4.1 seconds.



Braking upgrades for the BMW F82 M4.


We all know power is nothing without control. Furthermore, we know how hard these RWD oversteer machines can be to tame, so we've started with brakes.


M-Cars have fairly substantial OE brakes which can easily handle daily driving with the occasional track day. However, from an upgrade and maintenance POV, our disc and pad replacement is an essential improvement for all fast road and track day enthusiasts.


Standard F-Series M-cars are specced with 4-pot calipers mated with 380mm x 30mm discs, which are generously drilled for heat dispersion. Not bad right? We opted for our uprated disc and pad combo to improve overall stopping performance without breaking the bank.



Our 380mm grooved discs are a 2-piece design, allowing for far greater heat and gas dispersion to prevent warping vs the OE units. Subsequently paired with our RP650 fast road pads. Through extensive testing on the road and track, the result is an advanced ECE-R90-approved high friction material that delivers near-zero brake fade under high-temperature use, yet doesn’t require a warmup period.


To help improve the overall braking performance and appearance, we've replaced the rear 370mm x 24mm discs with our 2-piece floating grooved discs. Once again, accompanied by our tried and tested RP650 pads.



Studs, nuts, and spacers.


With the brakes taken care of, it made sense to install our 80mm stud and nut kit prior to setting the car back on the ground. If you've ever taken a wheel off even once, then you'll appreciate a stud and nut kit - we're saying goodbye to lining up the bolt holes, bashing the calipers with the wheel, and trying to avoid cross-threading the bolts!


We offer the studs in two lengths: 70mm or 80mm, supplied in a full set of x20.



We also wanted to achieve the widest possible setup on the OE 437M wheels without modifying the arches in any way and with no rubbing. And that's exactly what we did using our 12mm hubcentric spacers at the rear and 15mm up front.


By physically moving the wheel further away from the hub, we're able to achieve a flush fit to the wheel arches, whilst also providing additional clearance necessary to fit bigger brakes or coilovers.


Handling.


Full disclosure, our 'standard' M4 was equipped with some unbranded lowering springs. In true MMR fashion, we ripped out (carefully removed) the John Doe springs and replaced them with our tried and tested lowering springs, specifically designed for the F82 M4 platform.


Our kit lowered the M4 by 25mm at the front and 20mm at the rear.



Thanks to the carefully selected progressive spring rates, the ride quality remains unaffected and is nicer to drive at slower speeds. But push-on through the corners and the F82 chassis really comes to life, making it feel lighter, more direct, and with significantly sharper turn-in.


If all of that wasn't enough, our kit was developed to be fully compatible with either static or Adaptive M dynamic dampers - cool right?



Wow, wow, wow - these look and feel great on the road. As Goldilocks once said, this porridge is just right!


Modified BMW M4

The notorious crank hub.


Yes, our M4 is a low mileage stock example, but that doesn't make it invincible to the problematic crank hub failure that can (and most likely will) occur to the S55.


If you're an avid BMW fan, you'll already be well-versed on the infamous crank hub failure. But if you are new to all of this, the crankshaft drives the camshaft via a belt or chain with gears locked in place on both shafts with a keyway. The pistons and valve relationship should always remain the same to maintain piston-to-valve clearance. Any unintended slippage of the chain will vary the timing - ultimately leading to catastrophic engine failure, resulting in a rising piston meeting several fast-moving valves. Bad, right?



Wondering what the culprit is? Well, BMW's engineers secured the crank hub with a single bolt, accompanied by a friction material. No keyway or pins, just friction and prayers.


In the world of crank hubs, you generally have two options. Either a pinned or an unpinned crank hub. In essence, a pinned crank hub contains a selection of pin dowels that require holes to be drilled into the end of your crankshaft, uniting your crank and crank hub. An unpinned crank hub doesn't utilise the above-mentioned pin dowels.


At this point, we knew we wanted to push this car on the road and the track - ultimately leading us to our four-pinned crank hub solution.



Out with the old and in with the new! The centerpiece of our kit is the UK-made CNC-machined one-piece crank hub; created from billet EN36 steel that's been heat-treated with a 0.75mm case hardening, making it incredibly strong and durable. Accompanied by four aerospace precision machined dowels that mechanically lock the hub to the end of the crank itself. Plus a brand new OE bolt.


Of course, we need to drill the crank to install our pin dowels. We're glad we didn't do this on a driveway!



Capture plate.


Finally, as another option alongside tour uprated crank hub, adding a capture plate ensures that you have complete peace of mind - especially once tuning begins!



Our capture removes any possibility for the crank bolt to loosen with the engine's vibrations or harmonics. Our plate is an additional billet aluminium hat that securely bolts over the entire head of the crank bolt, making it literally impossible for the bolt to come undone.


Luckily for enthusiasts and customers, we sell our crank hub with or without the capture plate. It's your call.


BMW S55 engine

Full disclosure, we've only scratched the surface of the crank hub discussion. For more info on the topic in general or for more help of the specific solutions we offer, click here.


Exhaust upgrades.


To achieve the desired power numbers (hint hint), an exhaust system is a crucial piece in our 'Ultimate M4' puzzle. Power aside, there's the added bonus of vastly improving the sound with an after-market exhaust. But it's the improved flow which is most important to us.


It's a full stainless steel non-res system which we're testing for a potential future MMR product; with a redesigned back box layout and beautiful welds all round.


It's worth noting that the OE cats are still in place, making this a cat-back system. Rest assured, some sports cats will make an appearance in the future.



POWAAAH!


Okay, this is where it gets fun!


So far our M4 build has been extremely hardware heavy. And with the crank hub taken care of, it's time to increase peak horsepower, whilst adding features and improving overall driveability.


We're faced with two options; tune the M4 via conventional methods using ECU software or install our PCM which increases power and torque figures without leaving a trace.



Our PCM (Power Control Unit) works on a standalone PCB, which communicates with the factory ECU. Developed by our own in-house calibration team over the past 12 months, it allows the vehicle to safely increase power and torque levels throughout the entire rev range.

The best part is it's easily installed, and easily removed at any time without a trace. Cool, right?


We could talk about PCM all day, but for more detailed info click here.


Stock figures.


For good measure (pardon the pun) and out of interest, we ran the M4 on our own in-house 4WD SuperFlow dyno prior to software or a PCM.



The S55 rolled 435BHP & 535NM of torque at peak, on 99RON fuel - that's very close to OE figures.



Installing PCM and power runs.


Our PCM sits in the engine bay using the provided carbon fibre mount and hardware, while the wiring loom is plugged into existing sensors in the engine. That's a simple installation, providing you have a basic level of mechanical knowledge.

 

To keep the car smooth, safe and reliable, PCM's power levels have to be kept lower than traditional ECU calibrations. But of course, you'll love the power boost you get from PCM, combined with the driveability and efficiency gains.


With the PCM installed, we ran the M4 again on the same day, 10 minutes apart from our stock run.


The outcome? 485BH & 623NM of torque! That's a +50BHP & +88NM increase without opening the hatch on the ECU. On top of some fairly substantial gains throughout the entire rev range, you can clearly see an improvement in torque delivery low down.



We have't released our PCM for the F-Series chassis vehicles yet, but keep an eye on our socials for updates in the near future.


Panel filters.


During dyno testing, we decided to install a pair of our S55 performance cotton filters to improve airflow and reduce restriction once running some more power.



We've developed our own range of performance cotton gauze filters that easily drop into the OE airbox and provide excellent filtration properties. Combined with instant performance increases and induction noise enhancements from the get go.

 

Meanwhile, OEM-standards of design, quality, materials and construction means it fits and lasts like a factory part. They're even sold as a pair!

 

Put simply, we believe these are the best panel air filters you can buy.


That's about all for our F82 M4 at this stage. Tune in next time for more updates!


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