The E21 was the 1975 successor to the BMW 2002 and as such had a tough sporting image to live up to. The problem for the E21 was that it was bigger, heavier and (up until the release of the Euro 323i) produced less power than the 2002ti's 130bhp.
The E21 was only available in two door form from the factory although Baur made a T-bar convertible later on. Some US companies also made full convertibles, these are very rare.
Alpina's range took off where many others would finish, with a modified version of the BMW 323i. The engine was the standard overhead camshaft in-line six with the compression ratio lifted from 9.5:1 to 10:1. With special pistons and a re-worked cylinder-head which housed a new camshaft, it produced 125 kW (170 hp at 6000 rpm instead of 105 kW (143 hp at 5800).
Maximum revs went up to 7000 from 6400. Torque was lifted from the original 190 Nm (140 Ib-ft) to 210 Nm (154.7 Ib-ft) at 4500 rpm. Alpina also offered a series of kits which could further improve the car's performance and/or reliability.
Chief among these was an oilcooler; a 96-liter fuel tank; 255 mm diameter ventilated disc brakes; special suspension equipment using variable rate springs and Bilstein gas-filled shocks; light alloy rims, 6 inches wide at the front carrying Pirelli P7 195/50 VR 15 tires and 7 inches wide with 205/50 VR 1 5 P7 tires at the rear; front and rear spoilers; a special Alpina fascia panel; bucket seats; and the distinctive Alpina color scheme.
The Alpina BMW C1 retained the Bosch K-Jetronic fuel injection system and had a claimed top speed of 208 km/h (129 mph), with acceleration figures of 7.9 sec for 0 to 100 km/h (62 mph) and 28.9 sec for a standing start kilometre.
Jean Claude Giroix Alpina C1
Like all Alpina conversions, the car was officially homologated and fuel consumption was given as 6.1 liters/100 km (46.3 miles/Imperial gallon). A variation on the C1 was offered by the Alpina importer for France, Jean Claude Giroix, whose "JCG" model boasted cleaned-up pistons, valves, and valveseats, a modified camshaft, and a sports exhaust manifold. Figures for the JCG version were 127 kW (173 hp at 6600 rpm and 228 Nm (168 Ib-ft) at 4500 rpm, with a top speed of 213 km/h (132 mph).
Alpina B6: BMW 328i
The second car in the Alpina range, the B6, took the form of a 3-series body fitted with the 2.8-liter engine of the 528i model - modified of course. The 2788-cc six-cylinder engine was tuned along the traditional Alpina lines and retained the Bosch L-Jetronic fuel injection of the production model. It utilized an AFT digital map electronic ignition system. Power output was 160 kW (218 hp at 6000 rpm as against 135 kW (184 hp at 5800 rpm for the standard 2.8i engine.
Torque was 265 Nm (195.3 Ib-ft) at 5000 rpm compared with 235 Nm (173.2 Ib-ft) at 4200 rpm. Driving through a manual five-speed box and a 3.45 axle, this gives the B6 a 0 to 100 km/h (62 mph) figure of 7 sec and a time of 27.2 sec for the standing kilometre. Top speed is around the 230 km/h (143 mph) mark. Naturally, the B6 was not just modified in the engine department. Other modifications included improved suspension, Pirelli P7 tires, front and rear spoilers, a 96-liter tank, and Alpina trim items inside and out.