2002 BMW M3 - Dark Horse

Engine
3.2-liter inline six, AFE intake and software, Supersprint X-pipe, B&B Triflow exhaust

Transmission
Six-speed SMG

Suspension
Ground Control coilovers, Koni double-adjustable shocks, TC Kline rear shock mounts, UUC anti-roll bars

Brakes
Stoptech front assemblies and steel braided lines, Axxis ultimate pads

Wheels and Tires
Three-piece iForged Monaco, 9x19 (f), 10x19 (r)
Toyo T1R 245/35-19 (f), 275/30-19 (r)

Exterior
AC Schnitzer front lip and race wing, Mashaw carbon fiber hood, molded CSL diffuser, Euro bumper, custom body matched smoked taillights, Umnitza Predator headlights, Lumatek foglights

Interior
Carbonworks carbon fiber trim, armrests and e-brake, ACS pedals, Schroth Quick belt harnesses, Alpine IVA-D300 head unit, MBQuart amplifiers, component speakers and subwoofers

The first step to more power is increasing boost. This is accomplished by upgrading the ECU software. The factory chip is a Siemens/VDO 32-bit MSD80 engine management system. It maintains a factory boost pressure of 0.6 bar (8.82 psi) which comes from a pair of Mitsubishi Heavy Industries (MHI) turbochargers running in parallel. The MSD80 also orchestrates the Siemens/VDO piezo direct-injection injectors, variable cam timing, ignition timing, and cooling system. Many companies offer a standard ECU flash upgrade that will bring the 335i up to about 375 bhp for around $1,300. Vishnu Performance offers an alternative method for $1,300, in the form of a tunable computer that plugs into the stock ECU and uses an auxiliary solenoid (replacing the factory system) to control boost. For someone who likes to tinker, the Vishnu system might work. But for a trouble-free dealer experience, a flash upgrade could be the better choice.

The 335i uses a front-mounted intercooler with a design that is only efficient for the lower factory boost levels or small increases. With greater boost, excessive outside temperatures, or the use of only 91-octane fuel, upgrading to a larger capacity unit with an improved end-tank design would reduce the air charge temperature and result in more consistent, usable horsepower.

An exhaust modification on any vehicle is beneficial, especially on a twin-turbocharged application where excessive back pressure inhibits performance. The stock 335i dual-exit exhaust is configured so that each turbo basically has its own 55mm (2.17-inch) system. The best upgrade in this instance would be a turbo-back system that utilizes a pair of HJS 200-cell metallic catalytic converters. The trickiest design elements are the downpipes. The stock turbo exhaust housings face each other, making downpipes difficult to manufacture. Milltek Sport has a history of making difficult downpipes possible and has plans for such a system. Another available option is Agency Power's cat-back system featuring an H-pipe design and single rear muffler.

A potential problem with increased boost is the plumbing used to transfer boost from the turbo-chargers through the intercooler to the throttle body. The possible weak link is the factory driver-side plumbing, the part that incorporates the pair of diverter/bypass valves. The diverter valves are standard Bosch-style single diaphragm vacuum actuated valves with a one-inch inlet and outlet. The inlet and outlet ends use plastic tubes that have been heat-shrunk in place, making it difficult to upgrade. Since they are designed for factory boost levels, they are prone to leak when these levels are increased.

These few simple modifications should produce over 400 bhp. With so much power, reliability can be a concern. BMW has addressed this issue by departing from its normal magnesium/aluminum composite construction found in other BMW straight-sixes. The engine block in the 335i is true tuner hardware, featuring a new aluminum construction with cast iron cylinder liners. This newer, stronger design is much needed, since the combustion chambers will see peak pressure of 130 bar (1911 psi).