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BMW E30 Three Series - Mechanicals

Engines

M10 (chrome bumper cars)

Four cylinder 8 valve

1.5, 1.6, 1.8 and 2.0

1961 - 1987

M20

Six cylinder 12 valve

2.0, 2.3, 2.5 and 2.7

1979 - 1991

M21

Six cylinder diesels

2.4

1983 - 1991

M30 (South African 333i)

Six cylinder 12 valve

2.5, 2.8, 3.0, 3.3, 3.4 and 3.5

1968 - 1993

BMW m40 engine

M40 (plastic bumper cars)

Four cylinder 8 valve

1.6, 1.8 and 1.9

1988 - 2001

BMW m42 engine

M42

Four cylinder 16 valve

1.8 and 1.9

1989 - 1998

BMW s14 engine

S14

Four cylinder 16 valve

1986 - 1991

The 316 (actually 1800cc) and chrome bumper 318i used the trusty and reliable M10, The 316 used a Pierburg carb with electronic choke whilst the 318i used Jetronic-L fuel injection. Plastic bumper 316i and 318i models had a Motronic M40. Motronic was way in advance of the Jetronic-K system being used by VW and Audi in the late 80s.

The 320i used the M20 six cylinder, early versions had Jetronic-L and can be spotted by having the distributor at the side of the engine rather on the end of the camshaft as was the case in later Motronic cars. Much the same is true of the 2.7 used in the 325e eta. For 1988 US eta's had the 2.5i head giving a so called "super-eta" with a bit more power, this was due to the introduction of the E34 outside of the US and the cessation of eta head production.

The 323i was the only E30 to use Jetronic-K mechanical injection in it's first year but subsequent cars had Jetronic-L and gained around 10bhp in the process, they also used a good bit less fuel. The 325i was always Motronic.

The South African 333i used the M30 six. It was the only 3.3 M30 to have Motronic fuel injection in it's final form.

The M3 had the S14 16 valve engines in 2.3 and later 2.5 capacities, there were numerous versions with different outputs, see the M-Cars page. A 2.0 S14 was used in the rare 320iS.

Diesels used the M21 in either normally aspirated (1986 onwards) or turbo (1983 onwards) forms. From 1987 diesels had fly by wire throttles and Bosch DDE (Digital Diesel Electronics), at least they did on the early euro E34 version. I'd be interested to know about the later E30 diesels as DDE may only have been used on E34s.

BMW E30 front axle

E30 front axle and suspension.

BMW E30 rear axle

E30 rear axle and suspension.

Suspension

All E30s have Macpherson struts at the front and semi-trailing arms at the rear. The front lower control arms are L shaped with ball joints attaching them to the lower strut and the chassis whilst the rear attaches to the body via a rubber bushing. If this bushing fails it will cause wandering and a vibration under braking. Upgrading to a solid bushing gives better road feel, especially under braking. Four cylinder cars have slightly narrower struts but can be upgraded.

At the front the shocks are mounted inside the springs but they're separate at the rear which makes them much easier to replace. Front and rear anti-roll bars were always standard but sizes varied by engine size. Tourings, cabriolets and cars with //M-Tech suspension had thicker bars.

The rear subframe is held to the body by a pair of large rubber bushings, these don't last forever and can be another cause of wandering. The differential also has a large rubber attachment bushing but they seldom fail.

BMW E30 lower control arm

E30 lower control arm and steering tie rod.

Semi-trailing arm systems will have their geometry compromised by overly lowering the car, 25mm would be my limit. The M-Tech factory suspension was 15mm lower than stock and this works excellently. Overly lowered cars just look daft. The four wheel drive 325iX has different front struts and geometry.

E30s tend to understeer slightly but can be provoked into power oversteer, especially the more powerful versions. They are prone to trailing throttle oversteer if the driver backs off the throttle under hard cornering or worse uses the brakes. With any car you need to do all your braking before the corner instead of during but this is more important with older semi-trailing arm BMWs. If you're in a corner and have come in too fast stick with it and steer, don't brake or back off especially in the wet or else you risk spinning the car. E30s are far better than E21s in this regard.

Steering

E30s have rack and pinion steering. It was designed to be available with power steering only as an option so the number of turns lock to lock is annoying high. This can be remedied by fitting E36 parts but it's not just a bolt in job. M3s had a more direct rack but only in left hand drive sadly. Some say the power assistance is slightly overdone and delete it but I don't agree with this myself.

The rack is very durable and seldom fails unless the protective boots have been torn and let in debris. The tie rods are perhaps 100,000 mile items and a worn set can be felt as a vibration under breaking. Tie rods are cheap and easy to change.

Steering wheels have the same fitment as the E28, E32, E34 and E36. In the case of the E36 the height offset is a bit different. E21 steering wheels use a different spline pattern and won't fit.

BMW E30 E36 steering rack

Comparing the E30 and E36 steering racks.

Brakes

E30s have a four bolt hub design not shared with any more modern BMW, this makes upgrades pretty much impossible with factory parts. The exceptions are the M3 and South African 325iS whose brakes are derived from the E28 and it's five bolt hubs. E21s and 2002s use a different design of brakes which don't readily fit. It's possible to use Z3 or E36 Compact parts to upgrade to five bolt hubs.

Front discs are 260mm and those cars with rear discs use a 258mm diameter disc. This isn't that different from the Z3 which is around the same weight but Z3 brakes seem more positive. I don't think E30s brakes are less effective but I think that later BMWs have more servo assistance which gives them a more positive feel. The servo gets it's vacuum from the intake manifold and has an external non-return valve to preserve the vacumm in it. This valve should be checked if servo assistance seems lacking.

Four cylinder cars (except the 318iS) and 320i's without ABS have rear drum brakes. They work pretty well and whilst an upgrade to discs is possible by changing the trailing arm little is to be gained from it in general use. Four cylinder cars except for the 318iS have solid front discs instead of vented but they're the same diameter and upgrading is just a bolt on affair. Tourings all had rear discs regardless of engine size and many late 318i tourings had ABS.

The hand brake is a Porsche style device which operates on the inside of the rear discs top hat or activates the drum brake on cars without rear discs. Each side has it's own cable and they can be adjusted individually at the handbrake lever. There are also adjusters on each rear wheel which can be accessed with a flat head screwdriver through a wheel bolt hole without removing the wheel or disc.

On right hand drive cars a linkage rod is used to transfer braking force from the brake pedal to the other side of the car where the master cylinder lives. Unlike the E24/E28 the linkage is on the clean side of the firewall so isn't a problem. It's length can be adjusted to set the brake pedal height.

ABS was fitted as standard on the M3 and 325i but was optional on most other models. It works very well and is a real boon in poor conditions. Front stators are built into the hubs, rears are a replaceable ring which goes around the outer part of the transaxles.

Good quality pads from the likes of Textar, Pagid, ATE and other main brands are not expensive and it's crazy to skimp and use cheap substitutes. Brake fluid should be changed at least every two years.

Calipers were supplied by both Girling and ATE throughout the E30's life and a car could have either type. I've never personally seen Girlings on a UK plastic bumper car. The Girlings use a sliding guide pin which is more prone to sticking than the ATE design. Any benefits or advantages in driving from either type are minimal. When I recently needed a rear ATE caliper I found them to be in short supply.

BMW E30 automatic

Automatic 325i cabriolet, S/E/1-2-3 mode selector knob on centre console.

Drivetrains

Almost all manual E30s had five speed gearboxes. I believe four speed was available on some early euro four cylinder cars but I've never seen one. A dog-leg close ratio sports box was optional on early 320i's and 323i's. The normal boxes have a 1:1 fourth gear and 0.81:1 overdrive whist the dog-leg uses a 1:1 fifth gear and closer spaced gears below that.

Automatics were always provided by ZF and were four speed with 1:1 in third and overdrive 0.81:1 in top. Some very early cars had a three speed with no overdrive gear. The standard box had a mechanical kickdown linkage attached to the throttle body. The EH electro-hydraulic version was available as an option on the 325i (only seen it once on a late 320i), Motronic was needed to control it. The EH box had a sport mode which locked out the top overdrive gear and held the engine revs higher in the other three gears, this made overtaking much easier and is a huge improvement. It can be spotted by it's S/E/1-2-3 knob on the centre console.

A 25% limited slip differential was optional on the six cylinder cars and 318iS. Most cars had the so called small case differential with six screws holding it's rear cover but a larger cased version was fitted to the 325i and M3. I believe the larger case is the same as the E24/E28 diff (post 1982).

Almost all prop-shafts were two piece with a centre bearing and rubber "guibo" flex discs at the end. A handful of American 325's had a single piece shaft.