I'm preparing to do a tune up on my 560SEL later this week and went to confirm the firing order as I know it's different than that on Chrysler V-8s with which I am more familiar. What I discovered is that there are a couple of different cylinder numbering systems as well as firing orders out there and I'm curious if anyone knows why/how each developed.

Numbering Systems: Chrysler (and GM I discovered in my research) number the cylinders in the order in which they are encountered by a vertical plane moving from the front of the engine to the rear. Thus #1 is left front (from the perspective of the driver's seat) with #2 front right and #8 right rear. Ford and M-B use a different numbering system that I'm guessing may be somewhat of a "international standard" as I found it used in a Bosch handbook on all things automotive. The Ford/M-B system puts #1 at front right (from the perspective of the driver's seat) and continues back on the right bank before moving to #5 at front left on back to #8 at left rear. Again, I've found nothing that makes mention of when/why/or by whom these two systems were developed.

Firing Order: For ease of human memory, all manufacturer's start their firing order with cylinder #1 according to their own numbering system. Chrysler and GM appear to have always used the same firing order for their V-8s: 1-8-4-3-6-5-7-2. Mercedes appears to have always used 1-5-4-8-6-3-7-2 (which translated into Chrysler/GM speak would be: 1-8-7-3-6-5-4-2). Note that this is almost the same as the Chrysler/GM order with only cylinders 7 and 4 being interchanged. Ford, who uses the same numbering system as M-B, has used two firing orders during different time periods: 1-3-7-2-6-5-4-8 or more recently 1-5-4-2-6-3-7-8. A quick comparison shows that the more recent and, I gather, current Ford order is very similar to M-B and in fact is the same as the Chrysler/GM order once translated to the same numbering scheme. The earlier Ford firing order appears to have two pairs of cylinders swapped when compared to M-B: 3 & 5 and 4 & 7

Anyone have any insight this?

jlc

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Jeff

'87 560SEL 267K (177K on motor) Blue/Blue
'98 Buick LeSebre 60K (wife's car)
'56 Imperial Sedan 124K
Past Cars:
'67 Dodge Monaco 130K (Sold)
'87 Chrysler 5th Ave 245K and going strong (sold)
'73 Plymouth Satillite 175K (sold)
'96 Chrysler LHS 80K (totaled)