The BMW E46 M3 CSL is the pinnacle of the fourth-gen 3 Series range, but iconic as it is, there are some areas where it fell short. The owner of this modified M3 set out to build himself the ultimate E46 that would surpass even BMW’s own effort.

When it comes to the BMW E46 M3, we are of the same general opinion as pretty much everyone else – that it’s awesome. The ultimate form of the E46 has created an incredible legacy for itself and is such a highly revered car, even after so many years. And we never tire of seeing them. Whether it’s an immaculate example with just a few individual touches or something a little more full-on, we’d struggle to find an E46 M3 we don’t like, and we like Jack Cavanagh’s very much indeed because it’s been a project car built to be the best E46 M3 it can be.

Detailing enthusiasts, well, let’s face it, car enthusiasts in general, will recognise Jack’s Instagram and TikTok accounts as he’s the Brand Director for car care company Stjärnagloss, as well as the face of it. Jack describes his job as “selling car detailing products and dancing on TikTok,” and if you log on there or onto Insta, you’ll see him demonstrating the products with his cheeky, irresistible charms. It’s little wonder the brand has garnered such a devoted following on the UK modded scene, with Stjärnagloss sponsoring loads of sexy builds up and down the country. And that’s no surprise, considering Jack’s love of cars and modifying them, and BMWs are where his heart belongs.

Cav and his modified bmw e46 m3

Cav’s E46 obsession

“I first fell in love with an E46 when one pulled into our school playground. It was brand spanking new, and everyone crowded around it”, Cav recalls with a grin. “It was at a time when the new Need for Speed game had just launched, and everyone thought it was a GTR (I have no idea why, it wasn’t even silver or grey).” That was all it took to get him hooked on Bavarian metal, though his first ownership experience was less than stellar…

“Me and a friend bought an E30 318is for £250 from a guy. He had it sat on his driveway for around four years. We saw it as an earner,” explains Jack. “We took it home, cleaned it, got it running and thought we were going to be rich. Then we took it for an MOT and realised it had more holes than a cheese grater. Sat on it for around a year, then scrapped it for… £250,” he laughs, but the experience didn’t put him off, which is why we’re here now.

aerial shot of modified bmw e46 m3

Why BMW?

“Fast forward to actually being able to afford to buy an E46 M3, I looked at an Audi RS4, but it just didn’t do anything for me except sound good; AMGs are basically muscle cars, which I’ve never found appealing, and BMs just handle. Even from the factory, they are ‘down on power’ but make up for it so well In the corners,” Jack reasons.

“The E46 M3 I think has aged incredibly well. It is often regarded as the ultimate M by journalists, whom I really admire, and the price was reasonable. It has since gone up and come back down again, though, so who knows where it will end up on the value scale,” he shrugs. “I think 350hp in a sub-1400kg car is the sweet spot. I absolutely love the S54, and I think it looks mega,” Jack adds with a grin, and he’s definitely preaching to the choir.

modified bmw e46 m3 rear

Buying the BMW E46 M3 and build plans

“I found the car down in Cornwall, I think (bottom left of the country). It had some nice bolt-on bits but, unfortunately, it had been mangled together on driveways and wasn’t up to standard,” Jack tells us, but that wasn’t about to stop him, and, besides, it wasn’t going to stay like this for long. “We definitely had a plan when buying it, which was to make it the ultimate version of itself. The CSL was always the hero E46, but I think it could have been better. It needed better brakes, a manual box, and to be lighter,” says Jack with a twinkle in his eye.

“We wanted to make the E46 M3 GTS, the one that BMW never made: a lighter, more raw model. Much like what the E92 GTS represented – more track-focused and less refined/road going,” he says with building enthusiasm, and you’re looking at the result of that vision.

driving shot of modified bmw e46 m3

Improving the handling of the modified BMW E46 M3

Jack’s E46 M3 already had the manual gearbox that his perfect version of the CSL would have come with, so better brakes, less weight, plus the extra noise, performance and superb handling that the CSL offers, but taken to the next level were the goals for this build. In standard form, the E46 M3’s handling is very good indeed, but to elevate it beyond even that of the CSL, the chassis needed some work, especially as the suspension that came on the car was shot.

“I went for Bilstein Clubsport coilovers. After reading countless reviews, these were the best fit for the car’s ‘vision’,” explains Jack, “a predominantly track suspension that could also be used on the road. An extremely well-respected suspension brand with mountains of track car history. Lastly, a truly amazing company to work with that really cares about performance.

Then I poly-bushed everything, and a thicker anti-roll bar was already in but fitted incorrectly. Russ from Swift Performance nearly cried when I took the car to him for the first time,” laughs Jack, “but he’s since made it near-perfect,” he says with a satisfied smile. And on top of that, Jack has also added a purple tag steering rack, which is a little quicker than the stock M3 one, for even sharper response.

Apex wheels

Upgraded brakes and wheels for the modified BMW E46 M3

With suspension sorted and properly set up, the brakes also needed attention, and here, he’s opted for an F80 M3 Competition setup front and rear. That means beefy four-pot calipers with 380mm discs up front and two-piston calipers and 370mm discs at the rear, and this combo delivers serious stopping power and is a serious upgrade over the standard car’s brakes.

Jack’s M3 also needed some lightweight aftermarket wheels to go over those brakes, and his choice was the flow-formed Apex ARC-8. He’s running a 10×18” square setup, with the wheels mounted on a stud kit, along with spacers to clear the calipers.

The ARC-8 is a great-looking wheel, especially on any sort of track build, and they work so well here in matt bronze. The final touch was a set of seriously sticky rubber, and Jack’s choice of tyre really delivers: “The Nankang AR-1s are the real party piece of the wheels. They just don’t lose grip, and I stand by that statement,” he says with a laugh.

Diffuser and exhaust tips

Exterior styling modifications

At this point, the E46 M3’s chassis and brakes had now been suitably upgraded, and it was time to take a look at the car’s exterior. “The exterior styling bolted down to weight saving,” explains Jack. “I went for carbon and fibreglass everywhere possible. I don’t love wings on E46s as I think it kills the silhouette, but the CSL-style ducktail spoiler is beautiful, especially in carbon weave. The GTS-style carbon bonnet is aggressive and helps with cooling, so this felt like a no-brainer,” he adds, and these two additions not only look fantastic but also save a chunk of weight in one fell swoop.

The carbon and fibreglass bonnet looks awesome with its carbon vents, while the CSL boot lid is iconic, and leaving it unpainted adds an extra element of aggression to proceedings, plus it ties in with the carbon roof that’s also been fitted to this build, further reducing weight. Up front sit carbon grilles, carbon bumper intakes, plus a carbon splitter; look closely, and you’ll see that the front wings are lightweight vented fibreglass items from PSDesigns. The finishing touches are the carbon CSL-style diffuser and the custom BMW Stjärnagloss roundels. The result of all that is an E46 M3 that looks fantastic and more aggressive than stock without being over the top, and has lost plenty of weight in the process.

Roll cage in modified bmw e46 m3

Shedding weight inside the modified BMW E46 M3

Moving inside, the weight loss program has continued, and while the cabin isn’t too hardcore, it’s very much in keeping with the whole philosophy of the build. “I kept it simple and clean on the inside, I loved the suede and leather carbon buckets, colour-matched the cage to the wheels and dressed the trim in carbon skin (full carbon doesn’t exist on the internet, unfortunately),” Jack tells us. “I would love to remove the carpets and put carbon kick plates in, but worry how much louder it would be in the cockpit if we did. The sound deadening has already been removed,” he says, and that’s shaved a chunk of weight from the interior.

“I retrimmed the seats with Dave The Trimmer. That added some luxury back in as the seats were lightweight but dead to look at. I also took the opportunity to add the brand in there,” Jack grins, and the Corbeau carbon buckets look stunning, as a result. They’re equipped with Sabelt harnesses, and at the rear, the seats have been removed to make space for that cage. Other touches here include Alcantara gaiters with M tricolour stitching, an Alcantara-rimmed CSL steering wheel, plus a PSDesigns shifter. It all works together so well, giving the cabin that focused feel, and it looks great, too.

engine in modified bmw e46 m3

Modified BMW E46 M3 engine tuning

Finally, we come to the engine, and with the CSL acting as inspiration for this build, there was only ever going to be one must-have mod for the S54. “A Karbonius CSL carbon airbox. This was purely for the noise and the aesthetics. If anyone is hoping to get power from this, save your money,” Jack laughs. “We also sorted the cooling out – the radiator wasn’t efficient, and the fan was on a switch inside the car, so I put a CSF rad in and added a thermostat back in. The original exhaust was shot and rattled terribly, so Mad DP jabbed a beautiful cat-back from scratch. It sounds so much better now,” enthuses Jack.

“I took the car to TRS to iron out some wrinkles in the base map after the airbox was put on. The car achieved 361hp but with a great power curve – it’s very smooth and enough power, in my opinion,” he adds. “The Vanos and rod bearings had been done, but we re-did the shells before the Nurburgring trip. Misha Charoudin drove the car so we wanted to be careful,” he adds. Watch Misha’s video on his YouTube channel, and you’ll see just how much he enjoyed Jack’s E46 M3, so much so that he took it out for a second lap, which speaks volumes about how good this build is.

carbon airbox

Cav’s favourite modification

When he started this project, Jack set out to build himself a car that surpassed the CSL, and he accomplished that goal. It weighs the same as a CSL but has a roll cage, has the same power, but with better brakes and a manual gearbox, and it’s an awesome machine that’s been designed to perform on track, and it truly does. And with a build of this calibre, choosing a favourite mod among so many is no easy task.

“I’m torn between the airbox, as it just sounds sooo good, the Bilsteins, and the carbon roof and boot. All play very different roles, but each one was a bit of a pinch-me moment,” says Jack with a smile. “From a young age, I always thought it was such an honour and a privilege to be able to modify already great cars. These three mods felt and still do feel really substantial and ultimately really aren’t needed. It’s really just perfecting something that’s already great,” he says. “The roof was weird as the original had to be cut out. The Clubsports are an engineering work of art to look at and make the car so much more noble, and the airbox is just a symphony in D minor,” he grins, and that trio definitely makes this car something special.

rear 3/4 shot of modified bmw e46 m3

What’s next for Cav, Stjarnagloss and this modified BMW E46 M3?

There are, naturally, a few more mods to come, namely cams and a carpet delete, but Jack already has his hands full with his next project car, his G82 M4 CS. “We have just started making it more track-focused. Think of it as the M4 GTS-destroyer,” he grins, and of course that’s the direction he’s taking the new project in. And having proven he knows exactly what he’s doing with his E46 M3, we reckon it’s safe to say that with the M4, lightening is definitely going to strike twice…

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Photos: Ade Brannan.