They say it was the golden era of BMW. Dynamic, streamlined motor vehicles that had a discrete, yet regal and sporting presence, matched by no other. The E38 7 series comes to mind when writing these words, but all of it can also be used to describe even the smaller BMW offerings of the time, like the E46 3 series, especially in M3 trim.
Mechanical Distinctions
The E46 M3 is based on an already great car. The 4th generation 3-series was a true compact luxury car, that didn’t tire the driver on long journeys, but did serve a lot of driving pleasure, both in petrol and diesel form. The M3 built upon this, with much, much more. Apart from an entirely different engine, suspension setup, seats, body kit and brakes, there are a lot of smaller differences that complete the package.
Starting with even the most obscure little tidbits, the M3 had higher pressure fuel pumps, rated at 6 bar with a different fuel filter and a single, more efficient fuel scavenge line for increased fuel delivery performance. The rear end of the M3 will reveal a comprehensive overhaul as well, with a limited slip differential, and larger axles, coupled with a distinct sub-frame, rear trailing arms, springs/struts, sportier sway bar, and the addition of a V brace for reinforcement. Notably, the upper and lower control arms remain the same in both non-M and M models at the rear. The drive shaft, transmission, front brakes, control arms, struts/springs, sway bar, steering rack, tie rods, and front under brace are all uniquely configured to the M3. The M3's radiator, expansion tank, windshield washer reservoir, and secondary air pump also deviate from those in non-M models. Beyond mechanical distinctions, the M3 features an advanced DSC unit, utilizing a gyro under the driver's seat detecting body roll. Even the ECU stands apart, with the M3's box adorned with a fan on the cover, a feature absent in non-M 3 series BMWs.
Precision Engineering: M3's Unique Construction
The M3's bonnet is from lightweight aluminum, while the front wings, unique to the M3, are from steel. This combination aimed at the best possible weight distribution and performance. Even the M3 CSL, known for its lightweight design, retained steel front wings, suggesting a deliberate engineering choice by BMW. The front brakes utilized 'compound' discs composed of aluminum alloy for the center bell, ensuring low weight and efficient heat dissipation, while the working section features gray cast iron.
In terms of aerodynamics, the M3's original concept, displayed in 1999, lacked a boot lid spoiler, but one was added before production. The functionality of this spoiler remains debatable due to its small size, and similarly, the front wing vents, though aesthetically pleasing, are non-functional as they lack an aperture for airflow. Also worth pointing out is that the E46 M3 incorporates composite materials, with lightweight bumper bars made from a Kevlar/carbon fiber composite. This reinforces weight reduction without compromising structural integrity.
I mentioned all of this because there have been numerous times when I’d heard people saying the M3 isn’t that different from their 325i M-Sport. Quite frankly, they couldn’t be more wrong.
Innovations and Achievements of the S54 Engine
And then, there’s the engine, a product of masterclass engineering. The S54B32 engine in the M3 defies expectations by revving to an eardrum shattering 8000 rpm, producing 343 horsepower and displaying high torque characteristics. A substantial figure of 365 Nm can be experienced even at very low revs, with 80% of maximum torque available from 1750 rpm to 8000 rpm.While not fully dry-sumped, the S54 has a scavenge pump for sufficient oil supply for bearing pressure during aggressive maneuvers, mitigating concerns about oil pressure drop during hard cornering.
The S54 features iron-block construction and an aluminum head with individual throttle bodies and double-VANOS. Additional improvements encompass forged and graphite-coated aluminum pistons, a lightweight crankshaft, and reinforced forged connecting rods. A key objective of the S54 engine was surpassing the "100 horsepower per liter" threshold. The goal was achieved, placing the S54 in prestigious company alongside engines like the flat-6, found in Porsche's 996.2 GT3. Amazingly, the S54's development cycle continued long after the manufacturer's active support, and the aftermarket industry to this day persists in addressing and enhancing the engine's original weaknesses. Entire businesses have been established in order to repurpose and improve various unique components of the S54, like the VANOS system and rod bearings.
The hand-built S54B32 engine was a recipient of numerous accolades, including the International Engine of the Year Overall winner in 2001. The engine's impressive 104bhp per liter and meticulous hand assembly really underscored BMW's plan to deliver the best driving experience.
The driving experience
Out in the real world, the engine is a joy to experience, as it gives you a wide range of opportunities and emotions. It also allows you to drive the car in a very humane, regular way. The high torque figure and quite silent, smooth operation of the S54 at lower revs make it a calm city cruiser. You may as well forget that you are driving the ultimate compact BMW sports car of the era. The true character though, obviously, starts showing ones you put your foot down and start rowing through the gears.
The combination of power, braking, and nimble handling renders the E46 M3 a proper road weapon, leaving an enduring grin on any driver's face. Every major part of the M3 is designed to deliver its full sporting potential on the road. The regular M-Sport's suspension is often critiqued by owners for its stiffness and under-damping. In contrast, the M3 has a finely resolved suspension setup. The high revving, high power six becomes a wild screamer, with manageable power that doesn’t overwhelm. The body can be controlled very precisely, with minimal body roll, yet enough playful movement in the corners. Combined with its design, godlike engine and exhilarating dynamics, the E46 M3 is already a classic with a strong legacy and prices that are only shooting up.
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