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V8 Firing Orders

V8 Firing Orders

V8 Firing Orders

(OP)
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

RE: V8 Firing Orders

Interesting, but can you draw any conclusions from it?

RE: V8 Firing Orders

(OP)
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.

RE: V8 Firing Orders

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.

RE: V8 Firing Orders

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.  

RE: V8 Firing Orders

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

RE: V8 Firing Orders

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

RE: V8 Firing Orders

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

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RE: V8 Firing Orders

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: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: V8 Firing Orders

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.

RE: V8 Firing Orders

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

RE: V8 Firing Orders

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.

RE: V8 Firing Orders

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.

RE: V8 Firing Orders

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.

RE: V8 Firing Orders

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

RE: V8 Firing Orders

(OP)
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.

RE: V8 Firing Orders

  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 ?

RE: V8 Firing Orders

(OP)
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

RE: V8 Firing Orders

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.

RE: V8 Firing Orders

It's beautiful, But.. I don't see my favorite ford firing order 15426378  represented. numbered front to back looks like  12734568 ( I suppose front to back makes more sense, but far be it from me to question the wisdom of our ford ) probably just a mix up in the translation.  

RE: V8 Firing Orders



12734568, reading left to right

It just looks weird to me when you get two cylinders on the same bank firing one after another, like 73 and 68 in the example above.

RE: V8 Firing Orders

there it is !  yes at 68 they are right next to one another. it happens at 31 in 2 of the others above. the point of some of the earlier posts is that it has to happen somewhere. so 18547236 in the middle above is the oddball. what goes on there ?

RE: V8 Firing Orders

Maybe it (18547236) has a flat plane crank.

Regards

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RE: V8 Firing Orders

Or maybe it fires at around about 120 deg before or after TDC on one cylinder.

Regards

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Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: V8 Firing Orders

Ford cylinder numbering scheme with #1 cylinder on the left side of the engine (typical GM), with the middle throws opposite hand to the original SBC?


Norm

RE: V8 Firing Orders

And the firing order of a Detroit Diesel 8v71  would be?



www.retallickeng.com.au

Was told it couldnt be done, so
i went and did it!

RE: V8 Firing Orders

(OP)
A two-stroke V8 (e.g. DDC 8V-71) firing order would likely be quite different from a 4 stroke firing order, whether 360 or 180° crank.  A 4 cyl two-stroke already has a two-plane crank and even (90° separation) firing order so ideally a two-stroke V8 would have 45° phase separation for the whole engine and 90° phase separation on each bank.

RE: V8 Firing Orders

hemi,

this is the firing order, 1L-3R-3L-4R-4L-2R-2L-1R

Not sure on cylinder numbering.

www.retallickeng.com.au

Was told it couldnt be done, so
i went and did it!

RE: V8 Firing Orders

(OP)
As expected, the 2-stroke V8 firing order does not have any consecutive events on one bank.  Using conventional numbering, it would be 16587432.  You can see opposite cylinders are paired.  That's probably an inherent feature of a two-stroke 90° V8 with 45° offset crankpins, which I'm guessing is the configuration.

RE: V8 Firing Orders

Historically, maintaining the correct A/F ratio of the 5/7 adjacent firing clyinders has been a problem  because of their location in the firing order and as it relates to cylinder cooling or the lack thereof.

The 4/7 swap simply moves the adjacent firing cylinders to the front of the engine, thus they get first shot at the water pump and it makes it easier to jet the motor when carbs are used. Obviously, the 4/7 swap is not as critical if a reverse flow setup is employed.

John

RE: V8 Firing Orders

Most of the SBC I have seen put the water into the front of the block AND out of the front of the head.

The holes in the deck are designed to restrict flow enough to stop high flow due to shortcutting of flow at the front and stagnant water water at the back.

This would suggest the coldest cylinder but the hottest head at the front. This would suggest 4/7 swap has no advantage nor disadvantage, except to line the pockets of cam grinders and to cause a non standard firing order that may lead to incorrect wiring of spark plug leads.

Regards

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

RE: V8 Firing Orders

Actually, with the 4/7 swap, the average temps of the 4/2 cylinders are always cooler than the 5/7 cylinders.

I would suggest you stop suggesting and start measuring!

Regards

RE: V8 Firing Orders

Then how does reverse flow change the situation.

Regards

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

RE: V8 Firing Orders

Also, many who do the 4/7 swap have highly modified engines and therefore quite likely have different temperature profiles across their engine, so measuring one or two examples would not be an accurate representation. This swap is quite popular in drag racing where they often do not even circulate the coolant and sometimes use no coolant other than ambient air and rich mixture.

Also, in a pair of cylinders, if one goes lean and therefore possibly hot, the other goes rich and therefore possibly cold, so we get one hotter and one colder, so how does colder water help the cold cylinder.

If the hot cylinder were to go into detonation, I could see your point, but I have never seen a detonation problem cured by the 4/7 swap.

I have seen detonation or chamber overheating problems cured by directing water flow to hot spots by changing water inlet or exit points or by changing the size of water passages in the deck. I have more often seen them cured by simple jet or nozzle changes.

I have only ever measured individual chamber temperatures by spark plug reading as that indicates the temperature inside the chamber, not way out in the water jacket.

If I was having trouble controlling temperature around a particular cylinder, I would try to correct the water flow rather than change firing order.

On a SBC I put my effort in this regard into getting more water between 3/5 and 4/6 as that is where exhaust heat causes gaskets to blow with std exhaust valve layout.

I fix charge robbing problems in the manifold, not the camshaft.

Regards

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

RE: V8 Firing Orders

With a single-plane or common plenum intake #5 will rob #7, aggravated by #7 running hot unless the 4/7 swap is employed. Adjacent firing cylinders are very difficult to jet properly...if #7 is just right the rest of the cylinders will be too fat; if the other cylinders are just right #7 will be too lean and if #7 is lean and hot it will detonate. The 4/7 swap helps lessen the possibility of detonation due to the cooler cylinder pair.

Look, its no big deal....people have been doing it for 30 years or more and it does not cost extra if the cam grinder has masters with the 4/7 lobe setup. I admit, I have not kept up with the latest technology and don't know what they are doing now.......and I certainly no longer use carbs.

You stated you could not find a plausible reason for the 4/7 swap and I simply gave you one that worked in the day.

John

RE: V8 Firing Orders

Note that the LS7 and the 4.6/5.4 Modular motors have moved their adjacent firing cylinders to the front of the blocks.

1-8-7-2-6-5-4-3 - LS7

1-3-7-2-6-5-4-8 - 4.6/5.4

Coincidence?

John

RE: V8 Firing Orders

While I am sure there are certain combinations and conditions where the 4/7 lobe setup "really works", I am just as sure that the cam manufacturers are "using" this as a method to sell additional camshafts.  I also put this in the same category as the Beehive and Conical valve springs that have re-appeared on the market.  And then there is always the Vibration Absorber Carb spacer if you need something else to think about.

Larry

RE: V8 Firing Orders

(OP)
You bring up conical springs... interesting, that reminds me that production Oldsmobile Rocket engines in the late 50's - early 60's had conical springs, if I'm not mistaken.  They must have had a good reason to do that in mass production - any guesses?

RE: V8 Firing Orders

Our 1911 Little Giant has conical valve springs.

Their reason may have been they did not know better in that day and age.

It may have been constraints with room.

Regards

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