inline six firing order is shown here http://www.gtsparkplugs.com/firing-o...-inline-6.html 1-5-3-6-2-4, 1 at the front of engine, 6 at the rear of engine

BMW Engine Firing Order and Cylinder Location (Bank-1, Bank-2), 4-cylinder, 6-cylinder, V8, V12-cylinder (US models):

M10 Single cam, 2 valves per cylinder, produced through 1985 (US)
S14 Twin cam, 4 valves per cylinder, produced for 87 through 91 M3 (US)
M42 & M44 Twin cam, 4 valves per cylinder, produced 1990 through 1998 (US)

Cylinder numbering is from front to rear; 1 at the front and 4 at the rear.
Ignition firing order is 1-3-4-2.
These engines have only one bank (bank-1). All cylinders (1 through 4) are considered bank-1.

6-cylinder (US models):
M20 Single cam, 2 valves per cylinder, belt driven camshaft, produced through 1991 (US)
M30 Single cam, 2 valves per cylinder, chain driven camshaft, produced through 1993 (US)
M88, S38 Twin Cam, 2 valves per cylinder, produced for M5 & M6 through 93 (US)
M50, M52, M54, S50, S52, S54 Twin cam, 4 valve per cylinder, produced 1991 through mid-2000s (US)
N52, N54, N56 Twin cam, 4 valves per cylinder, produced from mid 2000s to current (US)

Cylinder numbering is from front to rear; 1 at the front and 6 at the rear.
Ignition firing order is 1-5-3-6-2-4.
Engines produced through 1995, are generally considered as having one bank (bank-1). All cylinders are bank-1.
Engines produced from 1996-on are considered to have two banks (bank-1 and bank-2). Cylinders 1 through 3 are bank-1 and cylinders 4 through 6 are bank-2.

8-cylinder, V8 (US models):
M60, M62, S62 Twin cam (two cams for each bank), 4 valves per cylinder, produced from 1993 through mid-2000s (US)
N62, N63, S65 Twin cam (two cams for each bank), 4 valves per cylinder, produced from early 2000s to current
Cylinder numbering is 1 through 4 on passenger (right) side and 5 through 8 on driver (left) side. numbers 1 and 5 are at the front, 4 and 8 are at the rear.
Ignition firing order is 1-5-4-8-6-3-7-2 (except S65 = 1-5-4-8-7-2-6-3).
Bank-1 is the passenger side (cylinders 1 through 4), bank-2 is the driver side (cylinders 5 through 8).

12-cylinder, V12 (US models):
M70, M73, S70 Single cam (one cam for each bank), 2 valves per cylinder, produced through early 2000s (US)
N73 Twin cam (two cams for each bank), 4 valves per cylinder, produced from early 200s to current (US)
Cylinder numbering is 1 through 6 on passenger (right) side and 7 through 12 on driver (left) side. numbers 1 and 7 are at the front, 6 and 12 are at the rear.
Ignition firing order is 1-7-5-11-3-9-6-12-2-8-4-10.
Bank-1 is the passenger side (cylinders 1 through 6), bank-2 is the driver side (cylinders 7 through 12
https://blog.bavauto.com/10109/bmw-e...-6-cyl-v8-v12/

M50 engine details http://bmw3series.johnavis.com/blog/654/m50-engine-e36/