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. 22.214.171.124 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 126.96.36.199 14:24, 22 December 2006 (UTC)
- 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.
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.
- 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. 188.8.131.52 (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
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". 184.108.40.206 (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)