01 · Überblick
The four-valve below the M3
In 1989, BMW gave the E30 an engine of a kind it had not had before: the M42B18. 1,796 cc, four valves per cylinder, two overhead camshafts, 136 PS at 6,000/min. BMW Group Classic describes the intent with the motto “more car, more engine, more sport” and explicitly calls the four-valve technology a technology adopted from motorsport.
The M42 is a further development of the M40. The crankcase was carried over unchanged; everything above it is new. Instead of one camshaft, two; instead of two valves, four; instead of a timing belt, a duplex roller chain with a hydraulic tensioner, plus hydraulic valve clearance compensation and a higher compression ratio of 10.0:1. This makes the 318is the only series-production E30 with a timing chain — the entire timing belt issue of the M20 does not apply to it.
It also came from the factory with sport suspension and disc brakes all round, which was otherwise not standard in the four-cylinder E30. The catalytic converter was standard; a version without a catalytic converter never existed.
One clarification, because it is often passed on incorrectly: the BMW PressClub calls the 318is the “first four-cylinder with four-valve technology” in the 3 Series. This is only true if one excludes the S14 of the 1985 M3 — which is also a four-cylinder with four valves per cylinder. The correct statement is: the first four-valve four-cylinder in the E30’s volume line-up, outside of M GmbH.
02 · Historie
Two years in four dates
The shortest lifecycle in the E30 line-up.
- 1989 The 318is arrives with the new M42B18. 136 PS, sport suspension, disc brakes all round, Shadowline. Price 33,600 Marks.
- 1990 Baur builds 97 Topcabriolets based on the 318is, 29 of them as right-hand drive. Price 41,550 Marks.
- 1991 After 41,234 units, production ends together with the two-door E30 Sedan.
- 1992 The M42 moves into the E36 and remains in the line-up there until 1996.
03 · Modellübersicht
The 318is in the line-up
For comparison, the two neighbours: the M40 as an ordinary four-cylinder of the same size and the S14 of the M3, which is likewise a four-valve four-cylinder.
Quelle: Werks- und Literaturangaben · geprüft
Technische Daten anzeigen — komplette Modellmatrix
| Modell | Motor | Hubraum | Leistung | Bauzeit |
|---|---|---|---|---|
| 318is | M42B18 | 1.796 cm³ | 136 PS (100 kW) | 1989–1991 |
| 318i (for comparison) | M40B18 | 1.796 cm³ | 113 PS (83 kW) | 1987–1991 |
| M3 (for comparison) | S14B23 | 2.302 cm³ | 195 to 215 PS | 1986–1991 |
04 · Karosserievarianten
Karosserievarianten
Two-door Sedan
The only factory body of the 318is. There was no Convertible from the factory — the E30 full Convertible came as 320i, 325i, from 1990 as 318i, and as M3, but never as 318is. There was also no Touring with the M42.
Baur Topcabriolet
The only open variant: 97 vehicles, 29 of them right-hand drive, converted by Baur in Stuttgart. Price in 1990: 41,550 Marks. Two independent sources cite the same unit count.
05 · Motoren
Der M42
Crankcase from the M40, everything above it new. The M42 is the only series-production engine of the E30 with a timing chain and the only four-cylinder in the model line with four valves per cylinder outside of M GmbH.
M42B18 · 1.796 cm³ · 136 PS geprüft
Bore 84.0 mm, stroke 81.0 mm, compression ratio 10.0:1. 136 PS at 6,000/min, 172 Nm at 4,600/min. Controlled by a Bosch Motronic M1.7 with static ignition and one ignition coil per cylinder. Two things distinguish it technically from the rest of the E30 line-up. First, the duplex roller chain with hydraulic tensioner instead of a timing belt — eliminating the replacement interval that determines the fate of the M20. Second, hydraulic valve clearance compensation via bucket tappets; the M20 explicitly does not have this. A version without a catalytic converter never existed. The M42 came exclusively with a regulated catalytic converter.
Technische Daten anzeigen
| Bauart | M42 inline four-cylinder, two overhead camshafts, four valves per cylinder |
| Camshaft drive | Duplex roller chain with hydraulic tensioner |
| Hubraum | 1.796 cm³ |
| Bore × stroke | 84,0 × 81,0 mm |
| Verdichtung | 10,0:1 |
| Leistung | 136 PS (100 kW) at 6,000/min |
| Drehmoment | 172 Nm at 4,600/min |
| Motorsteuerung | Bosch Motronic M1.7, static ignition with one coil per cylinder |
| Ventiltrieb | Bucket tappets with hydraulic valve clearance compensation |
| Katalysator | standard, no version without catalytic converter |
| Engine production period | 1989 to 1996, in the E30 until 1991 |
Sources: BMW Group Classic, Wikipedia DE and EN (BMW M42, BMW M40).
06 · Schwachstellen
Reliability & Weak Points
- The profile seal of the lower timing case at the front of the engine. If it leaks, hot coolant and vapour enter the oil — in the worst case leading to bearing damage. Both Wikipedia versions describe the mechanism independently of each other; the German version states that all M42s are said to be affected. This is the central point with this engine.
- As a consequence, the cylinder head gasket is often suspected, even though the cause lies at the front in the timing case. Anyone buying a 318is should ask specifically about this and want to see proof of repair.
- Timing chain tensioners and chain guides wear. Revised plastic guides were only introduced from September 1993 — so all E30 318is have the early version.
- The timing belt ceases to be an issue. This is a genuine advantage over the M20 and an argument that is often overlooked when comparing the 318is against the 325i.
- Rust is the same issue with the 318is as with any E30 — see the buying guide.
- Worn trailing arm bearings on the rear axle, front control arm ball joints, porous rubber bushings, and the trouble-prone hydraulic headlight leveling system are common across the model line.
07 · Technik
Suspension, Brakes, Transmission
Fahrwerk
Bremsen
Transmission and axle
Gewicht
Technische Daten — Achsübersetzungen & Getriebe
- Curb weight
- 1,125 kg
- Final drive ratio
- 4.10:1
- Transmission
- five-speed transmission
- Limited-slip differential
- not standard
- Suspension
- M-Technic sport suspension, 15 mm lower at the front, 17 mm lower at the rear
- Anti-roll bars
- 20.0 mm front, 14.5 mm rear
- Brakes
- discs all round, ventilated at the front
- Top speed
- 205 km/h according to BMW Group Classic
- Acceleration 0–100 km/h
- around 10 seconds — no leading source, two secondary sources cite 9.9 and 10.0 s
- Diverging figure for top speed
- 202 km/h according to one database source. We follow the 205 km/h from BMW Group Classic but note the discrepancy. Not verifiable and therefore not listed: transmission type, individual gear ratios, brake disc diameters, steering type, and steering ratio.
08 · Kaufberatung
What matters: the profile seal
With the 318is, the buying guide differs from that of the 325i. The timing belt is no longer an issue; instead, a single component takes centre stage: the profile seal on the timing case. Everything else is standard E30 fare.
Gusset plates behind the front wheels, transition from A-pillar to sill — the most critical point on the E30.
Battery tray and the area beneath it.
Rear wheel arches.
Sills and jacking points.
Trunk: spare wheel well, area behind the tail lights, rear closing panel.
Frontscheibenrahmen.
The order is: first the bodywork, then the question of the profile seal, then everything else. A 318is with documented repair work at the front of the engine is worth more than one with fewer kilometers and an unclear history.
09 · Die Konkurrenz
The competition
VW Golf GTI 16V
The benchmark of the segment. Front-wheel drive, lighter, more practical, less refined at the limit. The 318is counters with rear-wheel drive, a timing chain, and body quality a class above — and is correspondingly more expensive.
Opel Kadett GSi 16V
The most powerful of the three, also front-wheel drive. Clearly below the BMW in price, and well below it in reputation and value retention.
Mercedes-Benz 190 E 2.0 (W201)
The only direct rival with the same basic concept: notchback, rear-wheel drive, premium aspirations. Tuned for more comfort, but without four-valve technology.
10 · Galerie
Bilder
The only two-door body the 318is came in — along with the M42.
11 · Quellen
Belege & Literatur
Leading sources are BMW Group Classic, the BMW PressClub, and Wikipedia. Figures from other sources have been verified at least twice. Where only one source was available, the figure does not appear on this page.