Talk:Firing order

Alternative firing orders?

It would be nice to see some discussion on alternative firing orders for 4 cylinder engines. For instance, the 2009 Yamaha R1 (Motorcycle) uses a crossplane inline 4 cylinder crankshaft, which does not fire at even 90 degree intervals as is common in 4 cylinder engines. Likewise, MotoGP bikes sometimes use a 'big bang' firing order, which fires all the cylinders within 180 degrees of crank rotation.

Unfortunately, I don't understand the benefits of these firing orders well enough to make an intelligent addition to the wiki article. The best I could do is repeat some of the manufacturers claims.

Firing order is based on more than just ignition timing

In a gasoline engine, the correct firing order is obtained by the correct placement of the spark plug wires on the distributor. In a modern engine with an engine management system and direct ignition, the Engine Control Unit (ECU) takes care of the correct firing sequence. Especially on cars with distributors, the firing order is usually cast on engine somewhere, most often on the cylinder head, the intake manifold or the valve cover(s).

This information is incorrect. The firing order is also based on the position of the intake and exhaust lobes on the camshaft, and the position of the crankshaft. For instance, with a 1-3-2-4 firing order, you could swap the ignition leads for cylinders 1 & 4, or 3 & 2. This would cause spark to occur at the end of the exhaust stroke and the beginning of the intake stroke. Likewise, swapping ignition leads for cylinders 1 & 3, or 2 & 4 would cause ignition to occur at the beginning of the exhaust stroke. In either cause, I doubt the engine would run (very well?)

It *may* be possible to change the firing order by rotating the cams and switching the plug leads. I suspect doing so would be possible on an inline 4, but question weather or not it would be possible on a more complex engine, such as a V-12. Doing so would throw off injection timing on an engine with sequential injection. I suspect it would cause other issues as well.

Obviously, these comments do not necessarily apply to diesel engines.

There are atleast 3 cylinder numbering conventions for 90 degree V8s used in vehicles.

First some basics on orientation. The back of the engine is nearest the flywheel. The right bank is on your right if you're at the back of the engine looking toward the front of the engine. Put another way, for rear wheel drive vehicle in right hand side of road countries, eg. US and Canada, left bank is on the driver's side and the right bank is on the passenger's side.

Ford: Counting from front to back on the engine:

1 2 3 4 on right bank,

5 6 7 8 on left bank.

Chrysler and GM-Except NorthStar(tm): Counting front to back on the engine:

2 4 6 8 on right bank,

1 3 5 7 on left bank.

Northstar (GM): Counting front to back on the engine on the engine:

1 3 5 7 on right bank,

2 4 6 8 on left bank.

In V8 engines there is usually an offset between the front of the right bank compared to the front of the left bank about equal to the width of the lower part of the connecting rod. This is because piston/connecting rods assemblies are identical and share a common journal on the crankshaft between the banks. Hence there are only 4 journals on the crankshaft for connecting rods. In the Chrysler case: "1" and "2" share one journal, "3" and "4" share a journal, etc. Typically the cylinder nearest the front of the engine is numbered cylinder "1".

In the Chrysler case the left bank is nearest the front of the engine. Hence cylinder "1" is on the left side of the engine. When the Northstar engine was designed it was determine that some space would be saved if the right bank was moved ahead of the left bank. Consequently the apparent flip, left to right, of the cylinder numbering.

These differences in numbering conventions gives rise to differences in the "firing order". As expected, the actual design of the crank shaft also affects the firing order.

• These numberings are IRRELEVANT without a list of the numbering pattern of the cylinders For example, the GM LS1 example has the exact same firing pattern as all Ford V8s (post 1988), the only thing that differs, is the cylinder numbering. 192.197.71.189 14:05, 22 December 2006 (UTC)
• Your Ford/GM/Chrysler numbering is backward. The left back is the left side, when you are standing in FRONT of the car 192.197.71.189 14:24, 22 December 2006 (UTC)

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Great! Now incorporate this into the article... MH 21:25, August 21, 2005 (UTC)

   There was an interesting development in V-8 firing orders in the late '60's.  Ford's Windsor class engines--302W and 351W--have different firing orders.  Ford reversed the position of the #2 and #3 crankpins location when they built the 351W.  Why?  They observed that the firing order used on the 302W caused unacceptably high peak stresses at the #3 and #4 crankpins and #4 main bearing when using that sequence.  Reversing those two crankpins (and the resulting change in firing order) cured the problem. The two engines appear externally identical to the untrained eye and this has caused lots of camshaft replacement calamities through the years by careless rebuilders.  
   GM subsequently followed this practice on their latest rendition of the "Big Block" Chevrolet-based engine curing a number of problems.  The Ford "385" series engines--the "C" or Cleveland, and the "M" or Modified Cleveland, in all displacements (302 Boss, 351M & C and 400M) all used the same firing order as the little 302W.  They were structurally much larger, beefier (and heavier) engines.
   Leading bank issues are design significant.  It greatly affects intake manifold flow design.  Ford engines traditionally have a right-bank leading setup as do the Buick, Olds, Pontiac and Cadillac engines.  The Chevrolet Small Block, and all Chrysler and AMC engines used a left bank leading design.  Ford, alone among the above, numbers 1-2-3-4--right bank, and 5-6-7-8--left bank.  The others use a 1-3-5-7--left bank (etc.) sequence.

Claude764 (talk) 02:12, 29 October 2009 (UTC)

V-12

If you had a 12 cylinder 4 stroke engine how can you determine how many degrees apart the firing intervals are,

A complete cycle for a 4 stroke engine is two revolutions of the crank, or 720 degrees. Simply divide 720 by the number of cylinders to find the spacing. A 12 cylinder engine would have 720/12=60 degrees of crank rotation between each cylinder firing. There are some (mainly two-cylinder motorcycle) engines and V8-derived V6 car engines that use an irregular spacing but for an automobile engine this formula is usually accurate. Rpvdk (talk) 10:18, 22 May 2008 (UTC)

Clarity on Directions

The section on cylinder numbering isn't very clear about its directional relativity. For example, when it says "left", is it left as viewed from standing in front of the car, looking at it, or left from sitting inside the car, looking out straight ahead?

For example, when standing in front of a car, looking at it, the steering wheel is on the left in Australia, but right in America, while, sitting inside the car, the steering wheel is on the right in Australia, but left in America.

This is where the confusion arises, and I think it should be clarified.

203.122.107.112 (talk) 14:07, 21 May 2008 (UTC)

Agreed. I've added a section explaining left/right as they are generally used in the automobile industry, and removed the superfluous left/right references elsewhere. I think this will make the article more readable. Rpvdk (talk) 10:18, 22 May 2008 (UTC)

The article makes more sense now with the explanation. I personally find directions like that a bit confusing, though, because we look into engine bays by standing in front of the car, not by being inside the car. The directions are opposite in the two cases, of course. For example, if a mechanic was working on a transverse-engined car, the pulleys would be on their left, but to a driver they're on the right. Since the article is about cars technically, I tend to have the mechanic's perspective. Just my opinion, though. 203.122.107.112 (talk) 10:50, 24 May 2008 (UTC)

That's the problem with left and right, it's all relative :) . I think this is one reason ships use "port" and "starboard" but that terminology never caught on for cars (it is used for aircraft sometimes). Anyway, most automotive technical manuals and parts books I've seen use left/right always as seen from the driver's seat; that way, the right front wheel is always the same one no matter where you stand :D Rpvdk (talk) 19:42, 24 May 2008 (UTC)

inline 6 firing order

hey, i'm really courius about inline 6 firing order, so they would get balance. can someone tell me, please. —Preceding unsigned comment added by 123xyz321 (talk • contribs) 11:20, 13 June 2008 (UTC)

Cylinder numbering for V6 and V12 engines

The section about cylinder numbering talks mainly about V8 engines, and doesn't mention cylinder numbering for V6 and V12 engines. The firing orders are pretty meaningles without cylinder numbering. Could anyone include the cylinder numbering for V6 and V12 engines to improve the quality of the article, so that the firing orders can be "applied". 203.33.160.179 (talk) 04:06, 10 November 2008 (UTC)

The V8 is used as an example. The cylinder numbering schemes discussed apply to to V6 and V12 engines as well. I know GM usually uses the "odd on one side, even on the other" scheme but manufacturers have been known to use different schemes for some of their engines. Sadly there is no 'one size fits all' rule here. Rpvdk (talk) 10:21, 10 November 2008 (UTC)

Proton Wira engine

I have removed the firing order 1-2-3-4 assigned to the Proton Wira VDO engine. This car uses the Mitsubishi Orion engine 4G13 or 4G15, which has a standard 180 degrees planar crank. Hence 1-2-3-4 makes no sense. I expect it comes from their V6, which has a firing order 1-2-3-4-5-6. http://www.ben9166.com/2011/08/4g134g15-17l-crank-shaft-stroker-kit.html Mike163 (talk) 20:25, 19 January 2015 (UTC)

Crossplane V8 has even firing order, it is uneven only within each cylinder bank

This part of the article would need correction:

(with the exception of the Crossplane crankshaft, which has an uneven firing order, found in most V8s and in very few Inline 4s, such as the Yamaha YZF-R1, and due to the 90° crankshaft arrangement rather than the 180° flat-plane crank, it causes the engine to have more rocking but less vibration than a flat-plane crank and thus no additional balance shaft is necessary)

Actually a 90° crossplane V8 has even firing interval, it is just within each cylinder bank that it has uneven firing: Crossplane

Cse78 (talk) 22:56, 10 November 2015 (UTC)

Agreed, and I would go further and suggest it doesn't make much sense to comment on the specific balance issues of one engine and ignore all others. A crossplane V8 has noticeably more crank vibration than a flat-plane precisely because of the uneven firing within banks (and also because of the start-stop motion of the pistons, which only matters in cases of "large" inertial forces i.e. high reciprocating mass or high engine speed), hence the torsional dampers fitted to them for decades and the endless tinkering with firing orders in that same period (irrespective of cylinder numbering differences). Contrast with the flatplane which rarely has vibration dampers and in recent times has almost universally had just the one firing order.

I suggest the sentence be removed altogether; engine balance is mentioned and linked to in the opening paragraph, although it's not made clear how firing order is affected by balance considerations and vice-versa, but such things require an exploration of a good deal of the possibility space in order to be clear. Identiti crisis (talk) 23:43, 30 November 2015 (UTC)

Incorrect entries on uneven and even firing lists

Some of the engines listed in the uneven firing list are even firing or have even firing variants; vice-versa for the even firing list.

Uneven:

• "Audi V10 FSI" - only some variants are uneven firing (Audi R8 / Gallardo); also links to Lamborghini_V10, but that page clearly states the early 5.0 variant in the first Gallardo was even-firing, also: [1].
• "GM Vortec 3500 Inline 5" - This engine in various applications sounds even firing (e.g. [2]), and there is not normally any benefit to uneven firing with this configuration (Honda's RC149, a 5-cylinder GP bike from the '60s, was uneven firing - effectively a straight six with one of the middle cylinders removed [3] - but they revved to around 20 000 rpm, which is something of a different league in inertial terms).
• "Mercedes-AMG V12s" - making a 60 degree V12 uneven-firing takes special attention that has detrimental crankshaft design aspects (split pins) and potential smoothness issues.
• "Aston Martin 6.0L V12" - Another 60 degree engine.
• "Chevrolet straight-6 engines" - Four stroke straight sixes were conceived as the mirrored / opposed pairing of three sets of two cylinders, much as the standard inline four is two pairs of two cylinders, purely for balance (specifically: no rocking couple). There is no way to get uneven firing with such a crankshaft.

Actually, that isn't true. You could fire e.g. 1 and 6 simultaneously and then proceed with the rest of the order as normal, skipping 6 when you otherwise would have arrived at it (1&6,5,3,[ ],2,4); there are numerous such possibilities. Quite why you would do this, I don't know. Identiti crisis (talk) 09:42, 1 December 2015 (UTC)

Even:

• "all Ferrari production engines" - all Ferrari V12s since 1992 have been 65° blocks (Ferrari_F116/F133_engine) with common-pin cranks [4]. They are therefore uneven firing.

I'll link the disputed entries to here. Identiti crisis (talk) 23:43, 30 November 2015 (UTC)

Corrected, this was obviously wrong. Dovatf (talk) 22:06, 25 January 2016 (UTC)

Flat 4 Firing Orders

The firing orders 1-3-4-2 and 1-2-4-3 appear to be essentially the same, just in reverse order. If we extend the sequence 1-2-4-3-1-2-4-3, we can extrapolate that 1-2-4-3 is identical to 2-4-3-1. If we reverse 2-4-3-1, we get 1-3-4-2. By extension, and taking into account (as mentioned elsewhere) that there's no clarity on left on right, I suggest that 1-3-4-2 and 1-2-4-3 are exactly the same. InfoPirate (talk) 20:43, 14 October 2023 (UTC)