Enhancing a BMW M3 E46 for the track

Words by Thomas Kramer

8,000 revolutions per minute, naturally aspirated, straight-six engine, rear-wheel drive – these are facts that make petrolheads listen. Yes, we are talking about the BMW M3 E46. This car features, next to a few other fine technical ingredients, the final evolution of the glorious M-straight-six engine. Whilst this engine is certainly a masterpiece of Bavarian motor engineering, there are quite a few other aspects which make the E46 an excellent basis for a track car; at around 1500kg it is relatively light car, it has a 50:50 weight balance and of course there is the already mentioned 343bhp engine, which sends its power to the rear-wheels.

Straight from the factory this car is good for a lap of the Ring in 8 minutes 22 seconds – on normal street tyres. With some modifications the M3 can easily be turned into a track beast that can deliver below-8-minute lap times. So let’s have a look at the step-by-step performance improvements you should make to your M3 before you head off to the Eifel…

Chassis & Suspension

Generally, the M3 chassis is of very high quality. Even cars with 100,000 miles on the clock are often in very good shape if they have been well looked after by their owners. The body is very stiff thanks to the factory front strut-brace. Front control arms and bushings in contrast are rather weak and need replacement between 60,000 and 70,000 miles on street-used cars. Track cars will need new parts more frequently, upgrading the bushings from rubber to PU or even Aluminium increases accuracy but puts a lot more strain on the chassis. So overall the M3’s front axle is not a big issue.

The rear axle in contrast needs a bit more attention. There are two major weaknesses: cracks in the body and the very soft rear trailing arm bushings, which make the car feel very imprecise under load or at high speeds – especially when they are worn out. All models of the E46 suffer from the body metal cracking on the back where the rear axle is connected to the body. Full chassis & suspension advice is available in the magazine.

The Engine

It’s perfect – almost. The engine is the last part that should be touched on any track M3. Significant power gains will cost lots of money. Before you invest £3,000 on a CSL-style carbon fibre airbox, or even more on a supercharger kit, make sure all the other areas of the car are state-of-the art.

On cars that have done some miles already it is a good idea to do a (partial) rebuild of the engine. The first M3 E46 models had an issue with engines detonating. Full engine advice is available in the magazine.

Gearbox & Drivetrain

There are two gearbox options on the E46: Manual six-speed and the famous SMG II (sequential manual gearbox). The SMG is based on exactly the same hardware as the manual gearbox; it only has an additional electro-hydraulic actuator operating the clutch and the gearbox. For track cars the SMG offers various advantages. The more obvious ones are that you can shift up and down while keeping both hands where they belong, on the steering wheel. Also the SMG can shift much quicker than any driver could do manually. A less well-known reason is that you can be certain an SMG-M3’s engine has never been over-revved. Full gearbox & drivetrain advice is available in the magazine.

Brakes and wheels

Good brakes are essential on any car, but even more so on a track car. The standard 325x28mm front disc brake setup on the M3 look great, but are not suitable for track use. The good thing is again there are many upgrade options available. The most obvious option is to turn to the big names like AP Racing, StopTech or Brembo and get a big brake kit. Upgrading the front brakes is sufficient, put some good pads on the rear brakes and these will work fine. Another less costly way of upgrading the front brakes is to combine some parts from the BMW menu. Full brakes and wheels advice is available in the magazine.

Summary

The M3 E46 is a fantastic car to drive on a track. Even without any upgrades you really feel this car wants to race! The engine lusts for revs, the steering is extremely precise and as the driver you get the impression the M3 is telling you, “Give me more! Hit the throttle! I want to go faster, boy!” If you mix in the right ingredients you can spice this Bavarian roughneck up to become a real track-beast.

Full story can be found in the magazine.