Double VANOS steplessly variable valve timing. In the S54 engine, Double VANOS varies valve timing on the intake and exhaust camshafts. Though this system appears in all other current BMW engines, in the M3 unit it varies timing over a wider range and contributes in a major way to the engine's stratospheric power output.


VANOS pressure pump. The M3 VANOS system has its own radial-piston hydraulic pump; in regular-production BMW engines the main oil pump supplies the pressure to operate VANOS. Integral to the exhaust camshaft's VANOS mechanism, the pump produces up to 120 bar (1740 lb./sq in.) of pressure to vary valve timing more quickly at very high rpm it reaches. BMW M refers to its VANOS system as High-Pressure Double VANOS; it is also used in the new M5's V-10 engine.


Unique valve mechanism. 3 Series Coupes and Convertibles' 6-cylinder engines employ bucket-type hydraulic lifters, actuating the valves directly with minimum noise and no periodic adjustment. For an engine with the S54's rpm potential, BMW M engineers needed less reciprocating mass.

To achieve this, they created a different actuating mechanism, using finger-type rocker arms. Pivoting on their own shafts (one on the intake side, one on the exhaust), these small arms provide the actuating surface between camshaft and valve. As the entire arm does not move the distance of valve lift, its effective reciprocating mass is less than its actual mass - and it weighs less than a "bucket tappet" in the first place. All told, the effective mass is 30% less; in turn, this allows lighter valve springs, which further reduce inertia. The system also has less friction.

As there is no hydraulic maintenance of valve clearance, it does have to be inspected periodically. It is unlikely that clearance will ever require adjustment, but if so it is done with shims (tiny metal discs of various thickness) without removing the camshafts.

Whereas the "regular" 325Ci/330Ci engines have a simplex (single) primary chain driving the exhaust camshaft and a smaller secondary chain driving the intake camshaft from there, the S54 has a full duplex (double) chain driving both camshafts directly. As usual with BMW engines, the chain is hydraulically tensioned and needs no periodic adjustment or replacement.


Extra-high compression ratio. At 11.5:1, the M3 engine has the next-highest ratio in current BMW production, topped only by the 12.0:1 of the new M5.


Machined surfaces. "Engineering finery" again: Combustion chambers and intake ports are completely machined, for smoothness that facilitates airflow. The exhaust ports are partially machined. For durability, the valve seats are of especially hard steel. A 3-layer stainless-steel head gasket ensures effective sealing of the head to the block.


Head casting and sealing. Extreme strength in the cylinder head is achieved by making it a single aluminum casting. Though elaborate, this construction also saves a significant 29 lb. And as this weight reduction is at the top of the engine, it helps lower the car's center of gravity.



Induction System:

BMW M tradition, state-of-the-art technology

The M3 manifests an important BMW M tradition: an individual throttle for each cylinder. Positioned much nearer to the cylinders than a single throttle can be, these bring atmospheric pressure practically right to the cylinder. The "lag time" inherent in airflow into the cylinders is thus greatly reduced and the engine can react more quickly to throttle movements.

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