Via the accelerator pedal and its two potentiometers, the driver gives the commands, in turn processed by the engine control module and received by a DC servo motor. The motor drives the throttle shaft through a tiny gearbox.

Upstream of the throttle bodies are the six intake trumpets, made of weight-efficient fiberglass-reinforced PA6 thermoplastic; these are laser-welded into the induction plenum of the same material to form a single assembly.


M Dynamic Driving Control provides Normal and Sport settings for throttle response. In Sport, selected via a console switch, the ratio of throttle opening to pedal movement is increased so that apparent engine response is even quicker. Even the transitional response of the electronic engine controls is altered to suit. Drivers tend to find one or the other setting more to their liking, or choose them according to driving conditions or mood. The system always reverts to Normal when the engine is started.

Together with the stepless VANOS, this elaborate induction system adds to the engine's immense breathing and fuel/air processing capabilities.



Exhaust system: Engineered for Free Flow

The M engine team developed one of the freest-flowing exhaust systems ever installed in a production vehicle. After the partially machined exhaust ports, it begins with two snaking stainless-steel headers serving three cylinders each.

These headers are formed under high pressure with liquid inside them, which ensures even distribution of the forming pressure and thus consistent wall thickness. In turn, this process allows stainless-steel walls only 1 mm thick (about 1/25th of an inch), not only helping save weight but also hastening engine warmup as there is less metal to heat up after a cold start. Each header is a single piece, thus not welded-up as are most headers.

For effective emission control during engine warmup, the catalytic converters are right at the headers. From the catalytic converters rearward, the dual exhaust system continues through a large, L-shaped muffler/resonator and four polished outlets that speak the authoritative tones of M Power. This elaborate and efficient exhaust system imposes very little back pressure on the engine, and of course this too contributes to the engine's power output.



High-performance lubrication and cooling

To help ensure adequate lubrication under the high cornering, acceleration and braking loads the M3 attains, the S54 engine employs a "semi-dry-sump" oiling system. Particularly in hard cornering to the left, it is critical to ensure return of oil to the pan; therefore, integrated into the gear-type pressure pump is a scavenging pump that collects oil from the right side of the small forward oil sump and pumps it back into the main, larger rear sump. This rear sump is almost completely closed off from the rest of the system, and thus able to hold the oil necessary for lubrication throughout the engine. Specific return passages are also incorporated into the intake (left) side of the engine to help ensure ideal oil flow under all operating conditions.

The graphite-coated aluminum pistons are cooled by oil spray; each valve's rocker arm is sprayed with oil just before it is loaded by its camshaft lobe.

A thermal sender monitors oil level and temperature. If the level drops low, a warning appears in the instrument cluster; the tachometer face includes the oil-temperature gauge.

The M3 cylinder head incorporates crossflow cooling; this promotes consistent temperatures from the front to the rear of the head, helping minimize distortion and wear under the extreme heat such a high-performance engine develops when its full power is being exploited.

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