V8 Firing Orders

[Lou Scannon]

Out of curiosity I have been "collecting" V8 firing orders. So far I have found 5 unique firing orders for a conventional 90 deg bank angle cruciform crank V8. For clarity, cylinder numbering is from the front of the engine to the back, so odds are on one bank, evens on the other.
They, along with their twins (cylinders numbered back to front), Ford numbering system equivalent, and a partial list of engines that use them are:

Original Twin Ford
12784563 15436872 15486372 Ford Flathead Lincoln Flathead Ford Y-block Lincoln OHV Buick Nailhead
18547236 14527638 18364527
18736542 12634578 18654273 caddy flathead Olds OHV
18726543 12734568 15426378 MEL wedgeblock Ford FE
18436572 15634278 13726548 Caddy OHV Desoto Firedome Chevy smallblock Pontiac Mopar B AMC 1st & 2nd gen Olds 2nd gen Porsche 928

 

[RossABQ]

Interesting, but can you draw any conclusions from it?

 

[Lou Scannon]

I suppose, but I don't have time at the moment. One observation I have is that the bottom one seems to be the most popular.

 

[EngJW]

There are not many possibilities for a V8 with a 90 degree crank. It only looks like a lot because of the different numbering systems.

 

[tangel]

This brings to my mind a related question - what is the purpose of the "4-7" firing order swap for Chevys that is touted by cam manufacturers to increase HP.

 

[MechanicalChef]

Correct me if I'm wrong, but wouldn't the "purpose" be to "increase horsepower?"

 

[SomptingGuy]

There are other goals. Refinement, longevity, etc...

 

[franzh]

Hmm, this is ironic! Just last night, I was reading my issue of Hot Rod magazine and there was a test of the Lunati Cams 4-7 swap. They claim a horsepower gain and one engine manufacturer claimed less stress loading on the mains. Ford stated they changed the firing order on their 5.0 and 5.8 engines for that very reason.

http://www.hotrod.com/techfaq/113_0701_lunati_cams/firing_order.html

Franz

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[patprimmer]

The Chevy 4/7 swap simply moves the 90 deg sequence adjacent pairs to another position. The charging robbing effect is identical except for being relocated from 5/7 to 2/4.

Cylinders 5/7 and 2/4 both have the intake ports grouped as pairs with only a divider wall between the ports so it does not alter the geometry of the 90 deg in firing order separated ports.

I have never seen a credible explanation as to how this helps anything other than cam makers profits.

One noticeable thing about the original SBC firing order is that it not only has most names in the list, it also has all the most performance oriented names in its list.

I wonder what firing order Jaguar, BMW, MB, Audi, Ferrari, Rover, Aston Martin, Toyota and Nissan use, that is after they are all converted to the Chev cylinder numbering system. That is by doing the obvious and starting at the big end journal closest to the snout as 1 and counting along in sequence to end at 8 closest to the flywheel.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[dicer]

The firing order thing like someone mentioned is generally because of some of the goofy methods of numbering the cylinders. Only some manufactures do it correctly, Chevrolet is one of them. Unless some of their newer models are now different.

 

[CCycle]

Somehow I had the notion that the Ford flathead V8s were 60 degree. Is this correct?

 

[patprimmer]

No

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[EngJW]

I looked back in my notes and for a 90 degree crankshaft there are 3 different firing orders. All of them have the same problem of two adjacent cylinders firing one after another except the location of the pair is different (as Pat has already said). Of course, if you renumber the cylinders you get what appears to be another firing order.

I don't recall what reasons were given for changing the firing order. It could have been torsional vibrations, or main bearing loads as someone else said.

The flathead Ford mentioned above is probably the V8 60. It was just a smaller version of the regular flathead, made around 1937. The 60 may have been the horsepower. The larger engine had around 100. They were so cute you wanted to cuddle them.

 

[Ataloss]

PatPrimmer wondered about the firing order of Jaguar V8s (90 deg V8, cruciform crank). The firing order is:
1A, 1B, 4A, 2A, 2B, 3A, 3B, 4B (from a Jaguar technical guide I downloaded from somewhere off the internet long ago)

I ASSume this is starting at the front of the engine (oddly enough, the technical guide does not specify). Converting to odd numbered cylinders on one bank and even on the other, this yields:

12734568

Bob
P.S. - someone check my work to make sure I converted it properly - it's been that kind of day.

 

[EngJW]

You got it right, for cylinders 1357 on the left and 2468 on the right. If you renumber the cylinders as 2468 on the left and 1357 on the right, the firing order becomes 18436572. I think that is the same as the small block Chevy.

Either way, the same two cylinders fire one after the other, 68 for one numbering system and 57 for the other.

 

[EHudson]

I believe some very early Lincolns had a 60 degree V8, during the Leland years.

 

[Lou Scannon]

After doing some more analysis, EngJW appears to be correct. My list boils down to 3 unique systems when you take into account mirroring the banks. Here's what I got:

Seed Reverse Mirror Mirror-Rev Ford
12784563 15436872 18736542 12634578 15486372
18547236 14527638 14527638 18547236 18364527
18726543 12734568 18436572 15634278 18654273

It's interesting that the second one is the same when mirrored & when reversed, and it's also interesting that I found no examples of an engine using this one.

 

[FoMoCoMoFo]

2 of the ford #s in your first post I recognize, not sure whats happening in the last. there are certainly at least two ways, 3 and 5 seem "odd" as others have stated finding an advantage is tough. maybe some subtle change in crank load dynamics ? nothing you would expect to make to make a measurable difference in perf. are all cranks created equal throw phase wise ?

 

[Lou Scannon]

You're right, I only found 2 distinct patterns that Ford actually uses, 15486372 and 15426378. The others are hypothetical Ford patterns. In my recent post, I should have converted the third pattern under "Ford" to the variant actually used, which is 15426378. I'll repost the list here with that corrected.

Seed Reverse Mirror Mirror-Rev Ford
12784563 15436872 18736542 12634578 15486372
18547236 14527638 14527638 18547236 18364527
18726543 12734568 18436572 15634278 15426378

 

[crysta1c1ear]

Pictures.

That looks pretty.
But I guess a bit of space between them would be good!

12784563

18547236

18726543

I just drew the firing orders.
This PC will be off most of the time, and when it is on, it is via a dial up connection with the whole village going through some multiplexing concentrator that effectively makes the modem useless. If the pictures don't show, you aren't missing much.