So what exactly are the differences between a 325e and 325i? What does that "s" mean in 318is, 325es, and 325is? Is the '84-'85 318i the same as the '91 318i? What the hell is a 325iX? And why do the M3s look so different than the rest of the E30s? This guide will attempt to explain the differences between the American spec E30 models. (If you are looking for actual specs, click here.)
The main differences between the 325e and the 325i are in the engine. Although both models have engines from the same M20 family, the 325e has more displacement than the 325i (2.7 liters vs. 2.5), but drastically less horsepower (121 vs 167). The "e" stands for "eta" (the Greek character for efficiency) and was the theme for the 325e, which was conceived during the gas crisis of the late 1970's. However, the 325e's long stroke motor helped contribute to its large torque output, and it actually has a higher torque rating than the 325i (170 vs 164). The "e" has a low 4800 RPM redline but a relatively flat powerband to compensate and a very conservative 2.93 final drive (2.79 for the earlier models) to allow for low freeway RPMs and increased gas mileage. In contrast, the sport oriented 325i was equipped with a much shorter 3.73 final drive (4.10 in some automatics) and a much higher revving engine (redlining at 6700 RPM), despite its smaller size. In contast to the 325e, the 325i has a hotter cam, dual valve springs, larger valves, larger intake manifold, larger throttle body, larger exhaust manifolds, dual pipe exhaust system, and self-diagnosis capabilities (through Motronic 1.1 and 1.3).
Any model that is simply badged "325" with no letters is equipped with the 2.7 liter eta motor. It was BMW's base model from 1986 until 1988 when it was phased out in favor of the 325i. In its final year, the 1988 325 (dubbed "Super Eta" by enthusiasts) was equipped from the factory with a 325i cylinder head, unique pistons, 325i exhaust system, and Motronic 1.1 engine management control, which bumped horsepower up to 127 and raised the redline to 5500 RPM. (An easy way to spot a Super Eta is its telltale 6000 RPM tach.)
Any model with an "s" suffix, such as 318is, 325es, and 325is, denotes the sport model, which only came in 2-door form. It can be easily recognized with its front spoiler with integrated foglights, rear decklid spoiler, and 14" BBS cross-spoke "basketweave" rims. It also featured a limited slip differential (optional on the 318is), bolstered sport seats, thicker swaybars, slightly stiffer shocks and front springs, and a leather-wrapped 3-spoke steering wheel (except '90 on, which had a 4-spoke leather-wrapped airbag wheel). The 325es and 325is also came with an on board computer, power windows/mirrors/sunroof, central locking, and a premium sound stereo system. In 1991 there was no official 325is model, although all of the aforementioned items were still available as the Sport package.
The "X" denotes all wheel drive and only came in 325iX form (there is no such thing as a 325eX or 318iX). It shares major components with the 325i, but used a different oil pan and pump (because of the front drive axle) and came standard with 15" BBS cross-spoke rims that featured a unique +41 offset. The 325iX came in both 2 and 4 door form and had side skirts and slightly flared fenders to differentiate from the RWD models.
The "c" denotes a convertible, although it is not an official BMW designation. Rather, it is used by dealers and owners to easily identify a convertible model. (Likewise, an "A", as in "325iA," is used to identify an automatic equipped car.) BMW North America imported the 325i convertible in 1987 and the 318i convertible in 1991; both of which were still in production in 1992 when the E36 was released because the E36 convertibles were yet not ready for production.
The racing derived M3 shares very little body parts with other E30s (it has 20 unique body parts) and came with a completely different motor. The M3 is easily identifiable with its flared fenders, body colored bumpers/moldings/mirrors, front spoiler, side skirts, rear valence, rear decklid spoiler, high trunklid, rear window clip, and roof-mounted antenna. It's engine, the S14 2.3 liter DOHC inline 4, was derived from the 3.5 liter DOHC inline 6 found on the '88 M5 and was intended for motorsport use. It featured a very peaky 7100 RPM redline, 10.5:1 compression ratio, 4.10:1 limited slip, and close ration gearbox. M engineers also equipped it with a larger fuel tank, 5-lug 15" BBS cross-spoke rims, and upgraded brakes (thicker and larger diameter ABS-equipped ventilated discs, heftier calipers, and a larger master brake cylinder). Interior upgrades were limited to red gauge needles, oil temperature gauge in place of the economy gauge, sport steering wheel, leather sport seats, rear armrest (replaced the center seat), and an M logo on the instrument cluster and shift knob.
At the opposite end of the spectrum was the 318i. The 1984-1985 318i was equipped with the M10 1.8 liter SOHC inline 4 (which was first seen on the 2002 and revised for use on the E21), capable of 101 horsepower @ 5800 RPM. It used the basic L-Jetronic fuel management system (as opposed to the more modern Motronic system used on the M20 and S14), and came with very limited standard equipment. It was hard pressed by its competition and was dropped after only 2 years of service. But the 318i badge returned for 1991 and featured a brand new M42 1.8 liter 16-valve DOHC 4-cylinder motor, putting out 134 horsepower and 127 lb-ft of torque. With a fairly lightweight body and a high revving powerplant, the M42 318i was a lively car and was BMWs new entry level vehicle, though it was only in production for one model year in the US.