Firing order
Firing order
The firing order is the sequence of power delivery of each cylinder in a multi-cylinder reciprocating engine. This is
achieved by sparking of the spark plugs in a gasoline engine in the correct order, or by the sequence of fuel injection
in a Diesel engine. When designing an engine, choosing an appropriate firing order is critical to minimizing vibration
and achieving smooth running, for long engine fatigue life and user comfort, and heavily influences crankshaft
design.
Ignition
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 the engine somewhere,
most often on the cylinder head, the intake manifold or
the valve cover(s).
For this inline-4 engine, 1-3-4-2 could be a valid firing order.
Various firing orders for different engine layouts
number of
cylinders
firing order
example
1-2-3
1-3-2
Saab two-stroke engine
BMW K75 engine
1-3-4-2
1-2-4-3
1-3-2-4
1-4-3-2
Most straight-4s, Ford Taunus V4 engine
Some English Ford engines, Ford Kent engine
Yamaha R1 crossplane
Volkswagen air cooled engine
1-2-4-5-3
Straight-5, Volvo 850, Audi 100
1-5-3-6-2-4
1-6-5-4-3-2
1-2-3-4-5-6
1-4-2-5-3-6
1-4-5-2-3-6
Straight-6, Opel Omega A
GM 3800 engine
GM 60-Degree V6 engine
Mercedes-Benz M104 engine
Chevrolet Corvair
1-3-5-7-2-4-6
7-cylinder single row radial engine
Firing order
1-8-4-3-6-5-7-2
1-8-7-2-6-5-4-3
1-3-7-2-6-5-4-8
1-5-4-8-7-2-6-3
1-6-2-5-8-3-7-4
1-8-7-3-6-5-4-2
1-5-4-2-6-3-7-8
1-5-6-3-4-2-7-8
1-5-3-7-4-8-2-6
1-2-7-8-4-5-6-3
1988 Chrysler Fifth Avenue, Chevrolet Small-Block
engine
GM LS engine, Toyota UZ engine
Porsche 928, Ford Modular engine, 5.0 HO
BMW S65
Straight-8
Nissan VK engine
Ford Windsor engine
Cadillac V8 engine 368, 425, 472, 500 only
Ferrari Dino V8 (F355)
Holden V8
10
1-10-9-4-3-6-5-8-7-2
1-6-5-10-2-7-3-8-4-9
Dodge Viper V10
BMW S85
12
1-7-5-11-3-9-6-12-2-8-4-10
2001 Ferrari 456M GT V12
20
1-12-8-11-7-14-5-16-4-15-3-10-6-9-13-17-19-2-18-20 Cadillac V20 engine
Although the vast majority of automobile engines rotate clockwise as viewed from the front, some engines are
designed by the manufacturer to rotate counter-clockwise to accommodate certain mechanical configurations. In
these applications, the firing order is shown in a reverse order (though it still starts with 1.) For the most common
inline configurations, this gives firing orders of 1-3-2, 1-2-4-3, and 1-4-2-6-3-5. In addition to the reconfiguration of
the plug wires or injector tubes, the valve timing must be accordingly modified.
Cylinder numbering and firing order
Notes on left/right and front/rear
When referring to cars, the left-hand side of the car is the side that corresponds with the driver's left, as seen from the
driver's seat. It can also be thought of as the side that would be on the left if one was standing directly behind the car
looking at it.
When referring to engines, the front of the
engine is the part where the pulleys for the
accessories (such as the alternator and water
pump) are, and the rear of the engine is
where the flywheel is, through which the
engine connects to the transmission. The
front of the engine may point towards the
front, side or rear of the car.
In most rear-wheel drive cars, the engine is
longitudinally-mounted and the front of the
engine also points to the front of the car. In
front-wheel drive cars with a transverse
engine, the front of the engine usually points
towards the right-hand side of the car. One
notable exception is Honda, where many
models have the front of the engine at the
left-hand side of the car.
Saab B engine, "firing order 1342" marked on inlet manifold. #1 is towards the
firewall (right side of picture).
In front-wheel drive cars with longitudinally-mounted engines, most often the front of the engine will point towards
the front of the car, but some manufacturers (Saab, Citron, Renault) have at times placed the engine 'backwards',
with #1 towards the firewall. One notable car with this layout is the Citron Traction Avant. This layout is
Firing order
uncommon today.
See also: Automobile layout
Cylinder numbering and firing orders for various engine layouts
In a straight engine the spark plugs (and cylinders) are numbered, starting with #1, usually from the front of the
engine to the rear.
In a radial engine the cylinders are numbered around
the circle, with the #1 cylinder at the top. There are
always an odd number of cylinders in each bank, as this
allows for a constant alternate cylinder firing order: for
example, with a single bank of 7 cylinders, the order
would be 1-3-5-7-2-4-6. Moreover, unless there is an
odd number of cylinders, the ring cam around the nose
of the engine would be unable to provide the inlet valve
open - exhaust valve open sequence required by the
four stroke cycle.
1-3-5-2-4 would be the firing order for this 5 cylinder radial engine.
In a V engine, cylinder numbering varies among
manufacturers. Generally speaking, the most forward
cylinder is numbered 1, but some manufacturers will
then continue numbering along that bank first (so that
side of the engine would be 1-2-3-4, and the opposite
bank would be 5-6-7-8) while others will number the
cylinders from front to back along the crankshaft, so
one bank would be 1-3-5-7 and the other bank would
be 2-4-6-8. (In this example, a V8 is assumed). To
further complicate matters, manufacturers may not have
used the same system for all of their engines. It is
important to check the numbering system used before
comparing firing orders, because the order will vary
significantly with crankshaft design (see crossplane).
As an example, the well-known Chevrolet Small-Block
engine has cylinders 1-3-5-7 on the left hand side of the
car, and 2-4-6-8 on the other side, and uses a firing
order of 1-8-4-3-6-5-7-2.[1] Note that the order
alternates irregularly between the left and right banks;
this is what causes the famous 'burbling' sound of this
type of engine.[2]
The cylinder numbering scheme used by some manufacturers on
their V engines is based on "folding" the engine into an inline type.
In most Audi and Ford V8 engines cylinders 1-2-3-4 are on the right hand side of the car, with 5-6-7-8 are on the
left.
Firing order
This means that GM LS V8 engines and Ford Modular V8s have an identical firing pattern despite having a different
firing order.
An interesting exception is the Ford Flathead V8 where the number 1 cylinder is on the right front of the
engine(same as other Ford V8's) but this cylinder is NOT the front cylinder of the engine! In this case number 5 is
the front cylinder. A similar situation exists with the Pontiac V8's 455 etc. where the cylinders are numbered like a
Chevrolet V8 but the right side bank is in front(like a Ford), this puts cylinder number 2 in front of number 1.
V8 Cylinder bank
Audi Ford GM & Chrysler
GM (Northstar
Only)
Right side of vehicle 1234 1234 2468
1357
Left side of vehicle
2468
5678 5678 1357
Ships
Contrary to most car engines, a ship's engine or a power plant engine is numbered from the flywheel end towards the
free end.
In ship and power plant V-type engines the numbering is A1... and B1... where the A-bank is on the left hand side
and the B-bank is on the right hand side, looking from the flywheel end.
Trivia
The neon lights on Flo's V8 Cafe in the movie Cars flash in the proper firing order for a Ford flathead V8.
See also
Two stroke cycle
Four stroke cycle
Engine configuration
External links
Firing Orders, Cylinder Numbering and Distributor Rotation for American V8 engines [3]
V8 Engines [4] - Analysis of firing orders and cylinder numbering of V8 engines
References
[1] "Boxwrench.net" (http:/ / boxwrench. net/ specs_index. htm). . Retrieved 2009-02-04.
[2] Reyenga, Craig. "Craig's website - V8 engines - exhaust sound" (http:/ / craig. backfire. ca/ pages/ autos/ v8-engines#sound). . Retrieved
2009-02-04.
[3] http:/ / boxwrench. net/ specs_index. htm
[4] http:/ / craig. backfire. ca/ pages/ autos/ v8-engines
