An interesting variant of the M20 engine was Alpina's C2. The first C2 combined the wider bore of the M20B25 with the slightly larger crankshaft of an M20B23, to create a torquier engine of 2552 cc. This version put out and , 74 units were built between 1985 and November 1986. After the C2 2.7 appeared in the spring of 1986, the 2.5 was slightly upgraded and gained 5 horsepower. However, to indicate its "little brother" position in the lineup, the name was changed to C1 2.5. When the September 1987 facelift model of the E30 was introduced, the 2.5 litre C1 was discontinued, although a few cars were finished into 1988.