BMW E30 Info

Rear Wheel Bearing

The E30's came with two sizes of the rear wheel bearings, the smaller 39x72x37 and the larger 42x75x37
(note that both inner diameter and outer diameter differs).

So what models came with small bearings and what models came with large bearings?

In general (at least in Europe), the following can be used as a general guide
• Early E30's came with small wheel bearings (39x72x37) (33 41 1 124 358)
• Late E30's came with large wheel bearings (42x75x37) (33 41 6 762 317)

But! There are plenty of exceptions!
• E30 325i always came with large wheel bearings regardless model year.
• E30 323i came with small wheel bearings up to 09/1985,
   after that they came with large wheel bearings.
• E30 320i always came with small wheel bearings, but if it was ABS-equipped AND
   manufactured after 09/1985, it came with large wheel bearings!
• E30 320i Touring and Cabriolet always came with large wheel bearings!

Emission Control Diagram (320i & 323i L-Jetronic)

Models sold in Sweden and Switzerland (maybe other markets as well) did have additional emission control equipment.

Emission control diagram for 320i and 323i equipped with L-jetronic.

Wiring Diagrams (L-Jetronic)

A typical L-Jetronic wiring diagram, taken from "Haynes - BMW 320, 320i, 323i, 325i - 1977 to 1987" (ISBN 1 85960 079 4).

A typical L-Jetronic wiring diagram, taken from "Haynes - BMW 3- & 5-Series" (ISBN 1 85960 236 3).

Fuses And Relays (318i, 320i & 323i 1985)

The picture is taken from a Swedish owner manual.

Location and description of the fuses and relays.

Fuses And Relays (318i, 320i, 325i, 325iCabrio & 325iX 1988)

The picture is taken from a Swedish owner manual.

Location and description of the fuses and relays.

Ignition Timing

These are the values given in the owners manual for 318i, 320i and 323i (dated 1985 and equipped with L-Jetronic).

  • BMW 318i 18° BTD @ 2000 rpm
  • BMW 320i 24° BTD @ 3000 rpm
  • BMW 323i 19° BTD @ 3000 rpm

Timing info for a 323i equipped with L-jetronic from 1985.

M20 Cam Identificaton

Details about cam identification.

M20 Heads

Three different head castings were used over the engine's production run.

The earliest was "1 264 200" aka the "200". These were used in all E21 320/6 and 323i and E12 520/6 engines and later in the E28 and E30 eta engines (eta denoting the 'efficiency' version of the engine, with a lower engine redline amongst other focused differences aimed at increasing fuel economy). In the earliest (pre-84) Euro E30 323i the "200" head was used as well.

The next version was "1 277 731" aka the "731". This head was the same as the 200 but featured larger intake ports.

The final version was "1 705 885" or "885" introduced in the 325i. Ports were further enlarged, valves were larger and the combustion chamber was redesigned to improve flow and thermodynamic efficiency. Used in the 325i and the E30 super eta engines.

Cross section of a "200" head. Cross section of a "731" head. Cross section of a "885" head.

M20B25/M20B27 Heads Machining Limits

Machining limits for M20B25 and M20B27 taken from the BMW workshop manual.

Exterior Lighting

  • Low Beam H1, 55W (12V)
  • High Beam H1, 55W (12V)
  • Fog Light Front H3, 55W (12V)
  • Direction Indicator Front BA15s, P21W (12V)
  • Parking Light Front BA9s, T4W (12V)
  • Fog Light Rear BA15s, P21W (12V)
  • Direction Indicator Rear BA15s, P21W (12V)
  • Brake Light BA15s, P21W (12V)
  • Reversing Light BA15s, P21W (12V)
  • Rear Light BA15s, R10W (12V)
  • Direction Indicator Side W2x9.5d, W5W (12V)
  • Number Plate Light Rear S8.5 38mm, C5W (12)

The first part indicates what kind of socket the light bulb has.

The second part tells you what kind of shape the glass has of on the light bulb (P for pear shape, R for round shape and so on) followed by the power rating (in Watt).

So a BA15s, P21W has a socket called BA15s and is a pear shaped light bulb rated to 21W. For more information take a look at the E34 Rear Light page.

The light bulbs with the sockets W2x9.5d has a little bit different socket since it's wedge shaped. The figures indicates the dimension and layout of the socket. The shape of the glass of the light bulb is usually wedge shaped (as indicated by W4W and W5W) but can also be tubular and you can sometimes see T5 or T10 but this indicates ONLY the diameter of the tubular glass light bulb itself - it doesn't say anything about the size of the socket.

The last oddball is the light bulb with the socket "S8.5 38 mm". The "S" indicates it is a so called Soffitte socket type and 8.5 is the diameter of the socket and 38 is the overall length. See the picture below for an explanation. The glass bulb type is "C5W" which stands for cone shaped and rated to 5W.

The important measurements of a Soffitte light bulb.

Engine Data

Engine Model Type Management Volume Bore x Stroke Rod Length CR Notes
M20B20 320i I6 Motronic 1990 80 x 66 130 9.8:1
M20B23 323i I6 L-Jetronic 2315 80 x 76.8 130 9.8:1
M20B25 (84-87) I6 Motronic 2492 84 x 75 135 8.8:1 (cat only 87-90), 9.7:1 (euro only 85-89)
M20B25 (88-92) I6 Motronic 1.1 2492 84 x 75 135 8.8:1 (cat only 87-90), 9.7:1 (euro only 85-89)
M20B27 (84-87) 325/e/es I6 Motronic 2693 84 x 81 130 9.0:1
M20B27 (88) 325 I6 Motronic 1.1 2693 84 x 81 130 8.5:1
M10B18 (84-85) 318i I4 L-Jetronic 1766 89 x 71 9.0:1 Bentley
M10B18 (85-85) 318i I4 1766 89 x 80 9.3:1 Forum
M40B16 (88) 316i/iS I4 Motronic 1.3 1596 84 x 72 8.2:1 Forum
M40B18 (87) 318i I4 Motronic 1.3 1796 84 x 81 8.8:1 Forum
M42B18 (89) 318i/iS/iC I4 Motronic 1.7 1794 84 x 81 140 10.0:1 Forum
S14 M3 I4 2302 93.4 x 84 144 10.5:1