The B9 was the first Alpina car based on the E28 platform. The production started in November 1981 and ended in December 1987. In 1985 the B9 received the engine from B6 3,5 and the name was changed to B10 3,5. A total of 577 cars were made.
When the B9 was introduced, the flagship of the 5-series range was 528i. But this engine isn´t based on the 2,8 litre unit, it is based on BMW´s 3,5 litre six. That engine produces 218 bhp in ordinary form but after Alpina has modified the cylinder head, fitted special higher-compression Mahle pistons and a new camshaft and reprogrammed the Motronic system the engine produces 245 bhp. The torque has increased to 320 Nm. The B10 version has the same engine as the B6 3,5. Go to the 3-series section to read more about it. That engine produces 261 bhp without catalyst and 254 with. The B9 has a 5-speed Getrag gearbox. A automatic gearbox was optional.
To handle the greater power, and performance, the B9 has new progressive springs and Bilstein gas-pressure dampers and 16in Alpina wheels with 205/55 tires at front and 225/50 at rear. The brakes are uprated at front with bigger, ventilated discs(284 mm).
Interior changes include Alpina upholstery, Recaro sportseats, a leather-covered steering-wheel, a new gearknob and new instruments. To ensure high speed stability, Alpina fitted front and rear spoiler.
For the B9, Alpina claims a 0-100 km/h time of 6,7 seconds and a top speed of 240 km/h. In Auto Motor und Sport´s test the B9 accelerated from 0-100 km/h in 6,9 seconds, 0-160 km/h in 16,0, 0-200 km/h in 27,3 seconds and had a top speed of 244,9 km/h. For the B10 Alpina claimed a 0-100 km/h time of 6,4 seconds and a top speed of 250 km/h.