Mosselman MSL620 tuning 620hp BMW M4 F83 Cabrio

WEAPONS-GRADE  620hp F83 M4 Cab

Since the M3 and M4 were launched, the modding community has really got on board with them both and we have been seeing some awesome examples over the years. Every new M car is always met with a lot of excitement but the M3 (and now M4) even more so because they are the people’s M cars; the M5 and M6 are aspirational, but the cost of getting into that club is prohibitive and running costs are scary even when used prices start to fall. The M3, however, has always been a lot more accessible; it’s never been cheap in the absolute sense, but it’s the kind of car that you can imagine owning. Used prices always level-off at a very reasonable point (so much so it’s a wonder that everyone doesn’t own one), and running costs have always been very reasonable given the performance. That the F8x M3 and M4 look so downright awesome and aggressive out of the box – arguably the most in-your-face incarnation of the M3 to-date – is a big part of the appeal but perhaps the biggest draw is the combination of performance and modding potential. The M3 has always been a quick car and performance has grown with each generation but, generally speaking, with the high-revving NA engines of the past it took a lot of money to get meaningful improvements in performance from them, though that didn’t stop those with the means from doing just that.

The adoption of turbo power for the F8x generation, however, changed all of that; with the S55 on-board, the M3 has gone from being a high-revving beast to an absolute torque monster, making the new range feel so much faster than previous examples thanks to the ease with which all that performance can be accessed and turbos also mean massive tuning potential. Just a remap or a tuning module will send power soaring north of the 500hp-mark and that’s just scratching the surface of what the S55 is capable of; MStyle has dug a little deeper with its Mosselman MSL620 M4 demo car and unleashed the full fury of that mighty motor.

“MStyle has dug a little deeper with its Mosselman MSL620 M4 demo car and unleashed the full fury of that mighty motor”

MStyle needs no introduction, though if you’d like one you can read our Company Profile about them over on, and the Essex-based tuning specialist has been part of the modded BM scene for 17 years now. During that time it has been responsible for modding more customer cars than you can possibly imagine as well as building some epic demo machines, like the M4 Cab you are currently staring at here. This isn’t MStyle’s first M4 demo build but, with new products being launched constantly and the car being so popular and having so much potential, it’s a project you can undertake countless times and never build the same car twice, and this really is an exceptional build.

The name of this M4 kind of gives the game away – you instantly know that it’s packing a whole heap of Mosselman mods and if you make an educated guess that the 620 badging refers to its power output, you’d be right, as MStyle has extracted 620hp from the S55 with a wonderful array of go-faster parts stuffed under the bonnet. These take the form of the Mosselman MSL620 tuning package, which comprises hybrid turbos, downpipes, full exhaust system, oil thermostat and ECU software, giving you everything you need to take your M4, or M3, from wild to wilder in one easy step. This car is also running Mosselman’s iTronic tuning module, which adds the very cool Aston Martin-style needle sweep on start-up, along with remote exhaust valve control.

Every component of the MSL620 package has been chosen specifically and they are all designed to work perfectly with one another; the downpipes remove the restrictive standard cats, massively improving exhaust flow and upping power in the process, with the cat-back exhaust system further helping to increase gas flow for more power. The oil thermostat might seem like an odd addition but, according to Mosselman, the MSL Motorsport thermostat that sits within the CNC-machined housing opens at 85°C, which results in a lower engine oil temperature, which in turn increases stable performance and reliability, which can only ever be a good thing, and it’s impressive that a component like that has been added into a performance package like this. Then we come to the turbos themselves; the stock, TF035 MHI-designed items are upgraded to a TD04 MHI frame with a 47mm compressor wheel and 41.3mm turbine wheel, with the turbos having been design and produced at Mosselman’s in-house turbo lair in the Netherlands, and the only thing that you need to take away from all that is that they’re got bigger internals and make more power, which is what matters.

So the business side of things has been comprehensively taken care of on this M4 but, as you can see, MStyle has also put a lot of work into ensuring it’s got the visual flair to match all that newfound power and this M4 makes a big impact. First of all there’s the paint, and who would have ever thought we’d be drooling over grey? Yet here we are and grey is most definitely in – the solid shade of Nardo on MStyle’s demo machine looks awesome, there’s just something about it, we can’t explain it but it just works so well. On the outside, the M4 has been slathered in carbon from MStyle’s own catalogue and the black weave works exceptionally well against the grey bodywork; there’s a three-piece performance carbon front spoiler set, which looks ultra-aggressive and angular and not only makes this Cab look even more ferocious than it normally does but it also works to bring the car lower to the deck and it looks awesome for it. It’s joined by a set of carbon front bumper blades and carbon kidney grilles and there are carbon side vents while the mirrors wear carbon covers. Carbon side blades add an edge of extra aggression to the car’s flanks while at the rear there sits a seriously sexy carbon racing diffuser, this being the wide version, which not only adds the central fins but also includes carbon side elements that fill out the rest of the bumper and it’s topped off with an RKP carbon boot spoiler. It all combines to make this M4 look positively evil and it’s got to be just about one of the most aggressive cars imaginable, a riot of angles and edges that give it the most intimidating road presence and we love it.

With EDC on board, MStyle has opted to stick to the stock dampers and instead has dropped the M4 via a set of KW Height Adjustable Springs, which allow you to retain the functionality and versatility of EDC while also allowing you to fine-tune the M4’s ride height. The drop they deliver here is spot-on, serious but also sensible, though there’s plenty of adjustment left for those looking to get really low. The stock wheels are fine but would have been completely overwhelmed here, lost among all that angular aggression and really wouldn’t have done this demo build any favours so MStyle has brought out the big guns, opting for a set of seriously-tasty BC Forged wheels. The 20”, two-piece, nine-spoke HC010s fitted here really suit the whole look of the car, the satin black finish sitting perfectly against the grey bodywork and the deep concave faces added an extra element of visual drama. The hefty 9.5” and 12” widths front and rear respectively not only fill out the car’s fat arches to perfection but also allow for some seriously wide rubber to be wrapped around them, essential with this kind of performance on board, and this M4 wears fat 265s up front and monster 325s at the back, meaning it’s got grip and traction in spades. The interior mods are far more modest, amounting to just a small selection of carbon additions, but they help to give the cabin a more performance-orientated edge, with the beautifully slim DCT shift paddles, steering wheel trim and DCT lever surround all finished in the mesmerising black weave.

Now, that’s all well and good, but how does it actually drive? Well, when someone chucks you the keys to a 620hp M4 it would be rude not to at least have a quick go and see what it’s all about, quick being the operative word… The first thing we have to discuss is just how loud this car is; it’s outrageously loud but, crucially, only when you want it to be. In Eco Pro mode, with the valves closed (or with the valves closed manually via the iTronic module), this M4 is extremely civilised. It’s still loud – even the standard car is loud – but it’s perfect for sensible, everyday driving. With the exhaust valves open, however, it’s a different story. It fires up with the most ridiculous explosion from the exhausts; it’s just the angriest noise you’ve ever heard and trying to describe it on paper feels futile. It’s an all-out aural assault, with crazy induction noises from under the bonnet and this outrageous exhaust note. Then there are the pops, crackles and bangs that happen when you lift off or change gear. Every gear change is accompanied by a whip-crack bark from the exhaust and then, occasionally, you just get the most outrageous gurgling, crackling cacophony and we lost count of the number of times it just made us laugh out loud. In terms of sheer entertainment value and putting a smile on your face, this M4 is worth every penny, and we haven’t even got to the performance yet.

Wow. Wow, is this car fast; obviously, you’d expect it to be with 620hp on board but numbers on a page fall short of coming anywhere near being able to convey how that feels out on the road. There’s monster torque everywhere in the rev range and it makes the M4 feel absolutely effortless. You want to go fast? Just stomp on the accelerator and you’re doing silly speeds in an instant. The mid-range shove is immense and just so addictive, the way it squeezes you into your seat and snaps your head back every time you punch the throttle – it’s awesome, but this isn’t just a one-trick torque pony because those bigger turbos loves to breathe hard and when you extend the revs they really come alive. The top-end hit of power comes in hard and fast and the eagerness with which the S55 revs out all the way to its redline and the way the power just keeps on coming is just breathtaking. The acceleration just doesn’t stop as you bang through each gear and, flat-out, this M4 feels like an absolute animal; it’s hard to imagine anything being able to keep up with it, it’s outrageously rapid and just the most awesome experience. Beyond that, it rides really well considering the combination of stiffer springs and 20s with slim sidewalls, but the upshot of that is that it feels absolutely planted, with virtually zero body roll and front-end grip and rear-end traction are just awesome. This means that, in the dry at least, you can really enjoy all of the performance this M4 has to offer.

With its Mosselman MSL620 M4, MStyle has built an absolute animal; it looks awesome, one of the outright most aggressive cars we’ve ever clapped eyes on and we adore the colour combo of solid grey and carbon fibre, it just works so well, but the star of the show here is that Mosselman tuning package. At £7595 installed, the MSL620 package is a hefty investment but one taste of what this car is capable of and you will be reaching for your wallet. The noise alone is worth the entry fee because it will never fail to have you grinning like a lunatic whenever you drive this thing, but the performance is just something else. It’s just so fast and it just feels unstoppable but, what’s most impressive, is that it drives so smoothly that it never feels like an old-school modified car. It’s easy to drive and it’s happy to be driven slowly, it’s just such an impressive performance package and the sign of a company that really knows what it’s doing because while anyone can build a fast car, it takes a lot to be able to build a good car, and this is a great car. If you’ve got an M3 or an M4 and you’re looking for the ultimate performance upgrade then stop looking because you’ve found it. If you’ve got the funds, make this happen – trust us, you will not regret it.

Contact MSTYLE [email protected] 020 8598 9115

DATA FILE MStyle F83 M4 Cab

ENGINE AND TRANSMISSION 3.0-litre straight-six twin-turbo S55B30, Mosselman MSL620 tuning package (£7595) comprising upgraded turbos, exhaust system, downpipes, oil thermostat, ECU software, Mosselman iTronic tuning module (£1395). M DCT seven-speed gearbox

POWER AND TORQUE 620hp and 553lb ft

CHASSIS 9.5×20” (front) and 12×20” (rear) BC Forged HC010 two-piece wheels in satin black (£3695) with 265/30 (front) and 325/20 (rear) Continental ContiSportContact 3 tyres, KW HAS kit (£529)

EXTERIOR Nardo grey, MStyle styling parts including threepiece performance carbon front spoiler set (£649), carbon kidney grilles (£269), carbon front bumper eyelids (£195), carbon side vents (£195), carbon mirror covers (£449), performance carbon side skirt extensions (£595), carbon racing rear diffuser wide version (£945), RKP carbon boot spoiler (£995)

INTERIOR MStyle carbon DCT shift paddles (£229), carbon steering wheel trim (£229) and DCT gear lever trim (£159)

Mosselman badges front and rear MSL620 badging hints at what this M4 is all about Cabin has been enhanced with carbon elements. Seriously sexy 20” BC Forged HC010 wheels. Carbon diffuser and beefy quad exhausts. Mosselman tuning package delivers 620hp. Solid Nardo grey paintwork looks stunning. Aggressive carbon aero elements.

“The acceleration just doesn’t stop as you bang through each gear and, flat-out, this M4 feels like an absolute animal”


How useful was this post?

Click on a star to rate it!

Average rating 4.5 / 5. Vote count: 11

No votes so far! Be the first to rate this post.


Jean-Claude Landry
Jean-Claude is the Senior Editor at, and, and webmaster of He has been a certified auto mechanic for the last 15 years, working for various car dealers and specialized repair shops. He turned towards blogging about cars and EVs in the hope of helping and inspiring the next generation of automotive technicians. He also loves cats, Johnny Cash and Subarus.