500whp Supercharged BMW Z4 M Roadster E85

500whp Supercharged BMW Z4 M Roadster E85

The Z4 M Roadster was already a hardcore soft-top, but the owner of this supercharged example has taken things to the next level and built himself a full-on Clubsport-spec performance machine.

Words: Elizabeth de Latour

Photos: 24Seven Photography

Club Zed

The owner of this E85 Z4 M Roadster has turned his soft-top all the way up to 11 and turned it into a hardcore, supercharged Clubsport build that’s been designed to thrill on both road and track.


500whp Supercharged BMW Z4 M Roadster E85

It’s a shame BMW never decided to revisit the idea of a full-fat Z M car again because while the performance variants we’ve had have been great, their predecessors were something really special. The Z3 M was a real wild child, an absolute riot of a machine that took no prisoners, and it would put hairs on the chest of whoever got behind the wheel. While the Z4 M added a degree of civility to proceedings, it was perhaps even more hardcore, with a razor-sharp chassis, while the S54 under the bonnet needs no introduction. The Z4 M, it’s fair to say, is a lot – of everything – but for one person, it just wasn’t quite enough. Not hardcore enough, not focused enough, and not fast enough. Matters were taken into his own hands, and the result is a supercharged Clubsport build that cranks everything up to 11.

500whp Supercharged BMW Z4 M Roadster E85 - engine

The man responsible for this X-rated Z4 M is Byron Walker. He owns a company specialising in detailing, vinyl-wrapping and PPF (@topwrapzltd, topwrapz.com), and he’s come a long way since his first taste of motoring in the shape of a K10 Nissan Micra. “I have loved the BMW brand all my life,” grins Byron. “The excellent driving dynamics, the power, and the engines are sublime. My first BMW was a 130i M Sport. I wanted to grow up from my Evo VIII 260 with similar power but more luxuries,” he reasons. “I have to say I found the 130i too grown up, but, man, what an awesome car that was; I was just too young to appreciate it. The N52 engine was and still is one of BMW’s best, in my opinion,” he says.

There is, of course, nothing sensible about the Z4 M, and it’s easy to see why it appealed to Byron so much. “The idea of getting the E46 M3 running gear into a two-seat sports car, what’s not to love?! There are lots of CSL parts on them from stock, and it’s the last car to use the legendary S54! I adore it!” he enthuses. “This particular car was my first proper sports car, with rear-wheel drive, a borderline exotic motor, all wrapped up in a cool-looking shell,” and it’s clear Byron is well and truly smitten with his E85.

500whp Supercharged BMW Z4 M Roadster E85

“The car was new from Sutton Coldfield BMW at the time. Well, I say brand new; I picked it up with 700 miles on the clock, as it was the dealer manager’s car at the time. So, technically, it wasn’t brand new, but it’s as close as it gets! I did the running in service with it, so it’s pretty rare to find one of these owned by the same owner from new, hence why I’ve been able to keep the condition so good!” he says with a smile.

While Byron has modded every car he’s ever owned, including Escort Cossies, Renault 5 GT Turbos, and RS Turbos, and he also owns a wild stripped-out, caged-up Metro GTI with Lotus Exige running gear, the plan was never to take things quite so far with his Z4. “I planned to love it and cherish it, maybe do a couple of mods, then things got a bit wild over the years!” he chuckles. “We have a lot of history together. I love the M platforms in general, and I felt this, at the time, was a dying breed. It turned out I was spot on! I now have one of the coolest cars on the planet, in my opinion,” he smiles. “This car has won three Concours trophies, yet still mixes with the best of them on the race track. Growing up, I would spectate at the local sprint circuit called Curborough Sprint Course. This car was built into a Clubsport-spec Z4 to compete on that circuit, which it eventually did, and did very well indeed, easily matching the GT3 times posted. What I love about sprinting is it’s you against the clock, so the car’s condition (unless you crash) will stay perfect,” he says. We love that Byron is really committed to his Z4, to driving it properly on track, while also cherishing it to such a degree that it’s good enough to scoop Concours trophies, and you have to respect that.

500whp Supercharged BMW Z4 M Roadster E85

Even in stock form, the Z4 M is all about that engine, and in Byron’s example, it really is the centrepiece of the build, and it’s undergone quite an evolution over the time he’s had the car. “The engine started as a stage 1 non-intercooled system, and over the next three years, from roughly 2010, I saved up to get the additional bits to make the stage 2 upgrade. Then I added a smaller pulley with a revised tune to get it to stage 2.5. This made approximately 500whp,” he grins, and that’s a hefty chunk of power, around 560hp at the flywheel if not even a little more. In stock trim, the Z4 M is no slouch, but this one is on another level.

The under-bonnet enhancements that have helped to send the power level skyward begin with the supercharger itself, a Vortech V-3 Si-Trim unit that uses a front-mount intercooler. On top of that, there are uprated Bosh injectors, a Setrab oil cooler, a K&N air filter, a 100-cell cat exhaust system and RPi GT straight-through silencers that don’t do a whole lot of silencing. The standard supercharger setup already generates plenty of power, but Byron’s additional 2.5 upgrades turn it into a vicious vortex that makes this Z4 M a force to be reckoned with, and it’s awesome. Unsurprisingly, with so much power now passing through the Z4’s chassis, suspension enhancements were required, and that was Byron’s next port of call, but with this being a track-focused build, he’s gone above and beyond here. “I wanted to create a highly capable Clubsport build, so every component chosen on this car, bar the engine upgrades, is lighter,” he says, and that shows just how committed he was to making this Z4 M as focused a machine as possible. “I went with KW Clubsport coilovers with the KW monoball solid camber plates, Rogue Engineering rear trailing arm bush limiters, billet rear top mounts, and camber shims to net -3.5° of camber up front,” Byron explains. “The brakes are AP Racing sixpot front calipers with 356mm discs and four-pot rears with 328mm discs, and the calipers are in special-order enamel red paint with white AP logos.” This selection of superior chassis upgrades has endowed this E85 with simply sublime handling. And while picking just one stand-out mod on a car of this calibre is no easy task, for Byron, it’s the chassis that truly shines. “If I had to choose one favourite modification, I think it would be the suspension, as the stock stuff isn’t great and really lets the car down. These upgrades have transformed this platform into a true road weapon,” he grins.

500whp Supercharged BMW Z4 M Roadster E85

Byron’s Clubsport theme continues on the inside of the car, where you will find a seriously sexy addition, or rather, a pair of them. “Interior-wise, I went with Tillett carbon fibre seats, as the stock seats look great but really don’t hold you in well enough,” says Byron. “The Tillett setup shed over 68kg from the car! Insane!” he exclaims with a smile. “The total weight of the car is now a fully verified 1380kg, 100kg less than the stock car. Since the shoot, the car has had a MOMO steering wheel fitted, the epic MOD.07 with an NRG neochrome quick-release hub,” he continues. “This lightweight, thin wheel adds so much feel to the already fantastic M3 rack,” Byron says, and this combo has transformed the interior.

500whp Supercharged BMW Z4 M Roadster E85

The carbon seats look absolutely incredible, like something straight out of a million-dollar hypercar or a purebred race machine, and they make this Z4’s intent incredibly clear. The MOMO wheel is the perfect partner for the seats, and not only gives the cabin that Clubsport racer look but also allows Byron to really connect with the car on both road and track. He’s also added a trio of gauges for boost, lambda and oil pressure, plus a Storm Motorwerks billet gear knob that really enhances the shift action.

500whp Supercharged BMW Z4 M Roadster E85

Of course, while the way this Z4 drives and handles were the priority for Byron, the aesthetics haven’t been forgotten about, either. Some touches are tucked away, like the carbon M Performance fuel filler cap or the exceedingly cool M-tricolour splatter-painted engine cover, while other styling additions are more immediately obvious, like the wheels, for example. “I originally had genuine CSL wheels, but every man and his dog has them in rep form, and they just got so played out!” laments Byron. “So I went with 260M wheels from the E92 M3. They are a tight fit up front and will rub unless you run very aggressive geometry,” he explains, and they look fantastic.

500whp Supercharged BMW Z4 M Roadster E85

For most people, bigger is better, but these 18s suit the Z4 perfectly. There’s a lot of detail to them, the rears have some serious concave, and we love the colour they’ve been finished in – it’s a subtle touch that makes them stand out. And beyond the wheels, this Z4 M has been treated to a small selection of subtle additional visual enhancements, like the tinted headlights and the custom side repeater covers, but Byron has chosen not to go overboard with anything. “The style is OEM, baby, why?!” he chuckles, “Because it looks so damn cool! It’s got some OEM Aero side skirts, which are worth an utter fortune nowadays, and the OEM M Performance side splashes modded from an M5 to fit. The whole thing was treated to a full paint correction and covered in the best PPF money can buy! It’s perfect,” he smiles, and even the original windscreen, the replacements for which are now on back-order, has also been PPF’d to keep it protected, and we admire that level of dedication.

Keeping things clean and simple was definitely the way forward. The Z4 has such a nice shape that has aged so well and still looks so fresh, and it’s at its best without unnecessary additions to our eyes. In a world where we’re used to owners wrapping up a project and moving on to the next one in the blink of an eye, it’s always refreshing to meet someone who’s been so committed to one car for so long. In Byron’s case, he’s owned this Z4 M for some 13 years now, and he’s not about to let it go. Having spent so much time, effort, and, of course, money (“It’s cost a fortune!” he laughs), there’s only one thing on Byron’s mind. Well, two things… “The only plans I have now are to love it and enjoy it,” he grins, and when you own a supercharged Clubsport-spec Z4 M Roadster, it’s impossible not to.

500whp Supercharged BMW Z4 M Roadster E85

The supercharger has turned this Z4 M into a beast, and Byron loves it.

Interior-wise, I went with Tillett carbon fibre seats, as the stock seats look great but really don’t hold you in well enough. The Tillett setup shed over 68kg from the car!

Carbon seats look absolutely awesome, and offer serious support in even the most extreme cornering situations.

18” 260M wheels look fantastic and really suit the Z4. Subtle styling additions include the custom indicator covers; this Z4 has scooped a few trophies in its time.

The engine started as a stage 1 nonintercooled system… I saved up to get the additional bits to make the stage 2 upgrade. Then I added a smaller pulley with a revised tune to get it to stage 2.5. This made approximately 500whp

TECHNICAL DATA Supercharged BMW Z4 M Roadster E85

  • ENGINE AND TRANSMISSION: 3.2-litre straight-six S54B32, stage 2.5 supercharger system comprising Vortech V-3 Si-Trim supercharger, front-mount intercooler, Setrab oil cooler, uprated Bosch fuel injectors, powder-coated mandrel-bent tubing, silicone hoses, K&N air filter, smaller 8.5 psi pulley, cast-alloy intake setup and Vortech Maxflow bypass valve, 100-cell cat exhaust system, RPi GT straight-through silencers, Vibra-Technics Race engine mounts, Hack Engineering billet oil filter housing, custom M tricolour splatter-painted engine cover. ZF Type-H six-speed manual gearbox
  • MAX POWER: Approx. 500whp
  • CHASSIS: 8.5x18” ET29 (front) and 9.5x18” ET23 (rear) 260M wheels, with 235/40 (front) and 265/35 (rear) Nankang NS-2R tyres, composite wheel studs and nuts, KW Clubsport coilovers, KW monoball solid camber plates, Rogue Engineering rear trailing arm bush limiters, billet rear top mounts, camber shims for additional -3.5° front camber, AP Racing BBK comprising six-piston calipers and 356x32mm discs (front) and four-piston calipers with 328x28mm discs (rear), calipers finished in special order enamel red paint with white AP logos, braided clutch and brake lines
  • EXTERIOR: OEM Aero side skirts, OEM M5 M Performance side splashes modified to fit the car, tinted headlights, custom side repeater covers, M Performance carbon fuel filler cap, full SunTek Reaction PPF, windscreen PPF
  • INTERIOR: Tillett carbon fibre seats, Stack boost, lambda and oil pressure gauges, Storm Motorwerks billet gear knob (MOMO MOD.07 steering wheel and NRG neochrome quick-release hub fitted after the shoot)
  • THANKS Top Wrapz Ltd
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