Specialty File
The car you see here was no doubt envisioned by a legion of Internet dreamers—breathlessly commenting, “Crank up the boost!”—mere seconds after BMW debuted the twin-turbo 335i for 2007. But it took five Dinan employees hacking away at BMW’s software for a year and a half to finally make it happen.
It was worth the wait. Steve Dinan has sold more than 2000 software upgrades for the 135i/335i, making it the most popular upgrade in his company’s 31-year history. And it’s easy to see why: For $2199, a simple download at one of Dinan’s 129 U.S. dealers immediately endows a 335i with as much as 384 horsepower and 421 pound-feet of torque (versus 300 and 300, respectively). Dinan notes that this is actually more like a 60-hp gain, as BMW’s twin-turbo inline-six comfortably makes more than the advertised 300 horsepower in stock form.
The car tested here goes a little further. Outfitted in “Stage 3” trim, the S3 335i has an oil cooler that is twice as large as standard, a bigger intercooler, a better-breathing carbon-fiber intake, and a freer-flowing exhaust that allows for 1 additional psi of boost versus the 384-hp setup (14 psi total versus 8.8 psi stock). The result is 408 horsepower and a bombastic 440 pound-feet of torque. But it doesn’t come cheap: The aforementioned mods total $8895.
Not surprisingly, throttle tip-in is jumpy as the newfound torque introduces itself. The engine is crazy responsive from 3000 rpm but starts to run out of steam between 6000 rpm and the 7000-rpm redline—the boost tapers off in order to keep the turbos comfortably below their 230,000-rpm limit. And for a turbocharged engine, it still sounds remarkably raspy. At 4.4 seconds to 60 mph and 13.0 through the quarter-mile, the S3 335i is about a half-second quicker than a stock 335i in both regards and nearly matches the last manual M3 we tested.
But even more impressive than the engine work is Dinan’s $4225 chassis overhaul, which includes stiffer springs that lower the 3 by half an inch, adjustable Koni struts and shocks with Dinan-specific valving, front and rear anti-roll bars that mimic the M3’s, front camber plates, a carbon-fiber front strut-tower brace, and new bushings. Also add $5399 for 19-inch forged wheels—they weigh just 20 pounds apiece—plus Michelin Pilot Sport PS2s (265/30 front, 275/30 rear).
These mods make turn-in substantially more eager, and those front tires—40 millimeters wider—effectively squelch understeer. Hold on for 0.99 g on the skidpad—that’s superior to any M3 we’ve tested—and be ready to countersteer when the rear end comes around, jauntily.
Part of what makes the whole thing so exceptional is that, despite the dramatically increased performance, almost nothing is sacrificed except for a ride that’s more brittle and too harsh for our Michigan roads. But the steering is still linear, and nothing has been lost in the way that forces build up; there’s zero nervousness, dartiness, or tramlining; and, astonishingly, the tuned car even weighs 66 pounds less than our last stock 335i. Plus, the S3 335i meets 50-state emissions regs, and Dinan matches BMW’s four-year/50,000-mile warranty. In fact, we couldn’t help but think that Dinan’s chassis tune is probably closer to the BMW ideal. And that’s saying something.
