Firing Order Variations

[jcantor]

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

[Johnhef]

I dont remember it offhand but the firing order (Zundfolge) is stamped on one of the valve covers.

standing in front of the car, facing the engine, #'s 1-4 are on your left side (passenger side of engine) and #'s 5-8 are on your right side (drivers side of engine).

Sort of like this:

REAR
4 8
3 7
2 6
1 5
FRONT

[jcantor]

John,

I know what the firing order is. That wasn't my question.

My question is why do some manufacturers use one order and others another? Why the different cylinder numbering systems as well?

jlc

[mbdoc]

The firing order af any engine depends on the numbering of the engine cylinders! In 1964 when MB built the M100 V-8 they "chose" their way of numbering & still use that today.

Having the right side of the motor being 1-4 with the right front #1 is 100% their choice!