What makes the S14 engine unique?
The E30 M3’s S14 engine was designed for racing applications and is therefore compact and high-revving. It combines the basic four-cylinder block from the M10 family with a four-valve head derived from the one used on the six-cylinder M88 and S38 motors. Special features of this engine include individual throttle plates for each cylinder, machined intake and exhaust ports, and a crankshaft with eight counterweights. Like the M88 and S38, the S14 does not have hydraulic lifters, and thus requires periodic valve adjustments.
How many versions of the S14 engine are there and how are they different?
BMW Motorpsort built five road-going versions of the S14 powerplant. The “standard” S14 engine has a bore of 93.4mm and a stroke of 84mm for a total capacity of 2,302cc. Without pollution controls, it is rated at 200 hp (DIN) at 6,750rpm and 176 lb/ft of torque at 4,750 rpm. A version of this engine equipped with twin in-line catalytic converters produces 195 hp (DIN) or 192 hp (SAE) and 170 lb/ft of torque at the same engine speeds. This was the only variation of the S14 sold in North America.
A second catalyst-equipped version of the S14 was introduced on the E30 M3 Cecotto/Ravaglia special editions in April, 1989. This engine produces 215 hp (DIN) at 6,750 rpm and 170 lb/ft of torque at 4,600 rpm. The increased power is largely due to a reprogramming of the Bosch Digital Motor Electronics (DME). This engine also became the standard European-spec E30 M3 engine as of September, 1989 production.
The most powerful evolution of the 2.3-liter S14 was introduced in the M3 Evolution II starting in March, 1988. Changes included new pistons that raised the compression to 11:1 (from 10.5:1), a more effecient air intake, lightened flywheel and reprogrammed engine management. This non-catalyst powerplant is rated at 220 hp (DIN) at 6,750 rpm and 181 lb/ft of torque at 4,750 rpm. These engines have white cam covers with the tri-color Motorpsort logo painted on them.
The final version of the S14 features increased cylinder bore (to 95mm) and a long-stroke crank for a new total displacement of 2,467cc. This engine was used exclusively in the 1990 E30 M3 Sport Evolution, built from 12/89 to 03/90. In addition to the increased displacement, the valves were enlarged and a more aggressive cam was fitted. Special nozzles sprayed oil under the pistons to keep them cool. All Sport Evolution motors were equipped with catalysts. Power increased to 238 hp (DIN) at 7,000 rpm, though peak torque decreased slightly (over the Evolution II) to 177 lb/ft at 4,750 rpm. These engines use the regular black cam cover but have red spark plug wires.