The most notable characteristic of the E30 M3 (relative to later M3 iterations) is its racing pedigree. It was campaigned by BMW as well as other racing teams including Prodrive and AC Schnitzer competing in many forms of racing including but not limited to Rally, DTM, Australian touring car and other series.
One of the main reasons for production of the road car was to homologate the M3 for Group A Touring Car racing. One of the reasons often cited for its creation was that it was to compete with the "2.3-16V"-model of the Mercedes-Benz W201 190E which was introduced in 1983, although this was only speculative. When the E30 M3 was in its final years of top level competition, the 2.5liter S14 engine in full race trim was capable of 340hp (250kW) plus, naturally aspirated.
The E30 M3 road car
The first road-going version produced 195hp (143 kW) (catalyzed model). Evolution models (not sold in North America) continued with 2.3liters but adopted revised exhaust-cam timing, increased compression along with the lack of a catalyst producing approximately 215hp (160kW). Later the Sport Evolution model production run of 600 (sometimes referred as Evolution III) increased engine displacement to 2.5L and produced 238hp (175 kW). 786 cabriolets were also produced, all by hand in BMW's Garching plant; at the time the 215hp (160kW) example was the world's fastest four-seat convertible.
Changes from the standard 3-series
The E30 M3 differed from the rest of the E30 line-up in many ways. The M3 was equipped with a revised stiffer and more aerodynamic body shell as well as "box flared" fenders to accommodate a wider track with wider and taller wheels and tires. The only body panels the standard model 3-series and the M3 shared were the hood and moonroof. It also had three times the caster angle of any other E30. The M3 shared larger wheel bearings and front brake calipers with the E28 5-Series. It also had a Getrag 265/5 5 speed gearbox, and rear differential with different final-drive ratio and 25% lockup.