The Devil in Interlagos Blue: Resurrecting a BMW Unicorn

In this exclusive ifndautoparts feature, we follow the journey of reviving one of BMW's rarest modern classics.

There's something seductive about faded glory that drew Dan Tetlow to this Interlagos Blue BMW E46 M3 CS - number 78 of just 241 UK models. Not a project for the faint-hearted.

"Since I was a lad, I've wanted this exact car," Dan explains, hand tracing the faded paint, his enthusiasm barely masking anxiety about buying one of BMW's most complex M cars.

For this restoration, Dan partners with Darragh of Everything M3 workshop, the BMW specialist whose hands have saved hundreds of M cars from the scrapyard. "They've got well-known complexities," Darragh says, already mapping out the battle plan. "Rod bearings. Boot floor cracks. VANOS issues. Head gaskets...". 

Dan's face tightens with each item. Welcome to M3 ownership.

Skeletons in the Engine Bay

First drive tells all. The SMG gearbox clunks into gear like sledgehammer on concrete.

"Mode one is gentlest," Darragh explains.

Dan flicks to mode five. The car transforms from sleeping beauty to beast. Upshifts slam through the drivetrain like gunshots.

Trouble appears fast. Steering wheel vibration. Something clunking underneath. Oil temperature climbing past 100°C despite the cold day. Then, a grinding erupts from the rear.

"That's the diff," Darragh identifies. "LSD clutches glazing over. Classic issue."

Dashboard screen flickers, pixels dying in patches.

Up on the ramp, Darragh inspects underneath. "Not so bad. Chassis looks clean."

For a car approaching 100,000 miles, the structure remains solid. No terminal rust. No cracked subframe. The boot floor, infamous failure point, shows no distress.

But the list grows: broken exhaust hangers, cheap diffuser, corroded sensors, leaking power steering, cracked belt, dripping chain tensioner.

Dan pulls out his phone and opens the ifndautoparts app. Parts list growing faster than speeding tickets in a 20 mph zone.

Heart Surgery, Bavarian Style

Two weeks later, the M3 lies torn open. Valve cover off, exposing camshafts and followers.

"Shim needs precise adjustment," Darragh explains. "Exhaust side 0.28 to 0.33mm, inlet 0.18 to 0.23mm. Get it wrong, they sound terrible when hot."

The valve cover gasket has hardened to useless rubber. "This guy's going in the bin."

The exciting change is coming. "We're cloning the ECU to run as a CSL," Darragh grins, holding up a map sensor.

Subframe dropped, revealing fresh work. Two new engine mounts. Replaced control arm bars. "Peace of mind."

Manual Salvation

The SMG system is condemned to removal.

"When they work well, they're great," Darragh shrugs. "But a manual box isn't going to let you down."

"It does feel lazy," Dan agrees. "But will it be as quick in manual?"

"Course not," Darragh admits honestly. "But you're in control. More driving feel."

Thanks to ifndautoparts, they've sourced a low-mileage manual box.

The brakes get attention. "Stopping power on cars from this era is under par."

They settle on M135i four-pot calipers with adapter brackets. Inside, seats come out for re-trimming, worn leather bolsters and shiny steering wheel addressed.

The Reveal

Dan returns to find Everything M3 in a new location - a vast, wood-panelled cathedral to BMW's finest.

"We're sorting everything for ifndautoparts," Darragh explains, pointing to racks of organized parts.

But Dan's eyes search for that Interlagos Blue.

"Ready?" Darragh asks.

The car sits gleaming, looking more factory-fresh than when BMW built it. "Seat bolster, all new leather. Armrest sorted. Steering wheel recovered with tri-colour stitching."

Under the bonnet, a massive carbon fiber piece dominates - the CSL-style airbox.

"Factory inlet had a MAF sensor," Darragh explains. "We've plumbed in a MAP sensor, wired it, coded the ECU. Runs like a CSL."

The Beast Awakens

Keys in hand, Dan slides into the freshly trimmed seat. First gear is notchy, "These 420G boxes are like that," but as they pull away, the transformation is sledgehammer-obvious.

When Dan drops to third and plants his foot, the car reveals its soul. The CSL airbox unleashes a throaty growl that sends shivers down your spine.

"Oh my days," Dan gasps. "Sounds lovely."

"With the 4.1 diff, you're running about 12% more torque," Darragh notes. "One of the best mods for a naturally aspirated car."

The car pulls clean, no vibration, knocking, or temperature issues. Brakes bite with authority, six-pot calipers now stopping.

Even on damp tires, rear wheels spin under power. No longer a tired sports car but a reborn weapon.

The Damage: £25,000

Back at the workshop: the bill. The list is extensive: upgraded brakes, powder-coated subframe, new bearings, refreshed interior, engine rebuild, manual conversion, suspension overhaul.

Grand total? Just under £25,000.

Dan doesn't flinch. "Worth every penny to get this car back to glory."

Parts Payback

"Need to get some bits up for sale," Darragh suggests, nodding toward stacks of removed components.

"If you're a car guy with a garage full of parts, get them listed on ifndautoparts," Dan says. "Get extra income toward your project, just like me."

Worth the Blood, Sweat and Tears?

That tired, broken M3 we started with is gone.The Blue Devil is in front of us is what BMW always intended: a pure driving machine.

Manual gearbox provides connection the SMG never could. CSL-inspired intake delivers the signature soundtrack enthusiasts cherish. Every bushing, bearing, and bolt has been sorted.

For Dan, it's childhood dream made real. For Darragh, another Bavarian thoroughbred back in ultimate form.

For the rest of us? A reminder that some cars are worth saving, regardless of cost. When that straight-six sings through carbon at 7,000 rpm, with manual slotted into third and perfect chassis beneath, you understand why these petrolheads endure such pain.

Bloody worth it.

Watch the Full Restoration Journey

Experience the whole process on ifndautoparts YouTube channel. From teardown to test drive, every nut, bolt, and decision captured.

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Tech Spec: the Upgrades

ENGINE

• CSL-style carbon fiber intake with MAP sensor
• ECU cloned to CSL parameters
• New conrod bearings with ARP bolts
• New gaskets, valve cover, seals
• Valve clearances adjusted to spec
• New engine mounts

TRANSMISSION

• SMG to manual conversion
• New clutch and flywheel
• New slave/master cylinders
• Short shifter mechanism
• 4.1 differential with new bearings

CHASSIS

• Full suspension rebuild
• Powder-coated subframe and arms
• New bushings throughout
• New wheel bearings
• Reinforced rear axle carrier

BRAKES

• CSL front discs with adapter brackets
• 135i front calipers
• Refurbished rear calipers
• New handbrake mechanisms
• New lines and fluid

INTERIOR

• Complete seat retrim with new bolsters
• New centre armrest leather
• Steering wheel in Alcantara with tri-colour stitching
• New window tint

COST

• Total investment: ~£25,000
• Parts recouped through ifndautoparts: [In progress]

Owner's Verdict

"It's a completely different car. The manual conversion transforms the driving experience, and that CSL airbox noise is worth the price alone. What Everything M has created is the E46 M3 that BMW should have built from day one."