all-wheel drive 325iX. An economy version called the 325e was released with a lower revving, more fuel efficient engine. The e is an abbreviation for eta, which is used to represent the thermal efficiency of a heat engine. To maximise low-rev torque, the 325e engine was the largest available in an E30 (aside from the 333i model, which was only sold in South Africa). The 325e engine had a longer stroke than the 325i version, with a more restrictive head, four cam bearings instead of seven, and single valve springs (instead of the dual valve springs used by the 325i version). For versions without a catalytic converter, the 325e engine produced at 4250 rpm and at 3250 rpm. By comparison, peak torque for the 325i engine was at 4000 rpm. The 1987 Series 2 update boosted the 320i to and the 325i to , and improved fuel economy. Six-cylinder diesel In 1983 the M21 engine was unveiled in the new 524td at the IAA, Germany. The M21 engine used a Garrett turbocharger (without an intercooler). The engine has a capacity of and uses mechanical fuel injection. In 1985 BMW introduced the 324d, a naturally aspirated version of the same M21 engine, which was popular in countries with a high motor vehicle tax. In 1987 an electronically controlled fuel pump was used which increased the torque output by . The updated engine has a smaller turbocharger, decreasing turbo lag. Drivetrain In total, six transmissions were available for the various models of the E30: four manuals, and two automatics. The E30 was offered with rear-wheel drive, or permanent all-wheel drive (325iX saloons and estates only). Manual transmissions 4-speed Getrag 242 — 316 and 318i models 5-speed Getrag 240 — 316, 318i and 320i models (with a different bellhousing for the 320i, to suit the BMW M20 engine, and another different bellhousing to suit the later M42-engined 318i/is). 5-speed Getrag 260 — 323i, 325e, 325es and 325i models. 5-speed Getrag 265 — M3 model (dog-leg shift pattern for European models and a standard H-pattern for North American models). Automatic transmissions 3-speed ZF 3HP22 — 1981 to 1985. 4-speed ZF 4HP22 — 320i and 323i models until 1985, available on all models from 1985 onwards. Suspension One of the features that added to the roominess of the E30 was the suspension. The front MacPherson struts and rear semi-trailing arm suspension were a compact arrangement