The BMW ///M3 is a high-performance version of the BMW 3 Series, developed by BMW's tuning branch BMW M. M3 models have been derived from the E30, E36, E46 and E90/E92/E93 3-series, and sold with coupe, sedan and convertible body styles. Upgrades over the "standard" 3-Series automobiles include more powerful and responsive (yet at times smaller) engines, improved handling/suspension/braking systems, aerodynamic body enhancements, and interior/exterior accents with the tri-color "M" (Motorsport) emblem.

The E46 M3, first introduced in October, 2000, appeared worldwide with the new 3.2 L S54 M-tuned engine. At the time of the car's introduction, this engine had the highest specific output naturally aspirated engine ever made by BMW (except in the McLaren F1), producing 343 horsepower (256 kW) and 365 N·m (269 lb·ft). It was only available in coupe and convertible bodies as the sedan version was dropped.

The E46 M3 was offered with a standard 6-speed Getrag transmission, but optionally came with a SMG drivelogic transmission (also known as the SMG II). This is the standard 6-speed Getrag transmission with an electrohydraulically actuated clutch pedal. Shifts are made via the SMGgear knob or the steering wheel mounted paddle shifters. The engine had a redline of 8,000 rpm. As with most M engines, the S54 again had 6 independent throttle bodies and this time electronically operated throttles (drive-by-wire throttle with no cable).

In the U.S., the E46 M3 came with similar engine output as the European version, unlike in the E36, whose engine was derived from the M50/52 series engine. Power was now at 333 bhp (248 kW; 338 PS) due to close-coupled catalytic converters closer to the engine exhaust ports. In 2009, Road and Track magazine announced the 2006 M3 with the SMG transmission as its favorite sports car of all time.

M3 CSL come with M3 bag (Kyosho)

 The BMW M3 CSL (Coupé Sport Leichtbau) was a limited edition version of the M3, with only 1,400 cars being produced for its 2004 model year run. The CSL was never released into the North American market, and was only available in two colours - Silver Grey Metallic and Black Sapphire Metallic. As its name suggests, an emphasis was put on reducing weight. The M3 CSL has a kerb weight of 1,385 kg (3,050 lb), 110 kg (240 lb) lighter than the regular M3. The CSL features many weight saving technologies taken from BMW's Formula One racing applications. A large proportion of the M3's sound insulation has been removed,electric seats, and navigation systems. Air conditioning and stereo systems could be retrofitted free of cost, but were not available standard. The CSL's unique body pieces are all crafted from carbon fiber reinforced polymer. Glass-reinforced plastics are used throughout structural points in the car.The rear glass window was replaced with lightweight plastic. Although the CSL loses a considerable amount of curb weight from its original version, the focus was put on strategically reducing or moving the weight in the car rather than the raw amount of weight that could be lost. This is to retain the ideal 50:50 weight distribution characteristics the E46 has. For example, the roof is constructed from carbon fiber reinforced plastic. While this only reduces the curb weight of the car by 7 kg (15 lb), it lowers the center of gravity of the car and decreases body flex. 
In order to improve the handling ability of the car, the entire suspension system was further refined. Specially developed racing springs and dampers are given to the CSL, and a tightened steering ratio (14.5:1 vs 15.4:1 on the regular M3) improves responsiveness. The braking system is also modified, with larger front and rear floating rotors and calipers from the E39 M5. The CSL is given a retuned dynamic stability control system with a "M track mode" setting that allows the car to be pushed to its absolute limits before being activated.
The 3.2L engine used in the M3, the BMW S54, has been modified to increased output by 17 hp (13 kW) and 5 N·m (1 lbf) over the European M3. This is achieved through a high flow carbon fiber air intake, modified valve and camshaft timing, and a retuned DME. However, the engine is further modified in order to reduce weight - it features a lightweight exhaust manifold and thinner exhaust piping. Additionally, the intake and exhaust manifolds are slightly straightened to improve engine responsiveness.

The CSL also has various aesthetic modifications over the standard M3. It received an aerodynamic lightweight body kit which included carbon fiber front splitters that improved downforce at high speeds by 50%, as well as a carbon fiber rear diffuser. The front bumper has a distinct hole that is used to draw cool air into the newly designed air intake. The boot floor is made of cardboard. The boot lid is redesigned to incorporate a raised lip, unlike the standard M3 where one is simply added on to a flat boot. The CSL was sold with distinct 19 inch lightweight forged BBS alloy rims that came with Michelin Pilot Sport Cup semi-slick racing tires. The interior of the CSL is redesigned with a sporty-weight saving theme. The CSL obtains fiberglass front racing bucket seats, and fiberglass backed rear seats. The center console, door panels and trim, and headliner are all formed from carbon fiber, and the steering wheel is redesigned with cruise control, stereo, and phone controls removed to include just a single button that activates the M track mode.

Unlike the standard M3, which was offered with a standard 6-speed Getrag transmission, or optionally a SMG drivelogic transmission (also known as the SMG II), the CSL was offered only with the SMG II transmission. This is the standard 6-speed Getrag transmission with an electrohydraulically actuated clutch pedal, similar to an Formula One style transmission. However, the CSL received a more advanced drivelogic unit than the standard M3 that was capable of making shifts in 0.08 of a second.