An engine consists of multiple cylinders. An engine having six cylinders is called six cylinder engine. Firing order of 6 cylinder engine is discussed in detail below.
These cylinders can’t be fired all at once because it would result in improper rotation, high magnitude of vibrations and high heat generation. To counter these problems, cylinders are fired one by one. One may think the sequence of firing would be 1,2,3,4 and so on. But that would also result in vibrations and high heat generation. So, an optimum firing order is decided which does not damage the engine health and works efficiently.
Types of 6 cylinder engines
The cylinders can be arranged in multiple ways in order to get the best efficiency.
According to the arrangement of cylinders, 6 cylinder engine can be of following types-
- Straight six engines- Also referred as inline engine, straight six engines are those in which cylinders are arranged in a straight line or placed next to each other. The engines may be inclined at some angles, then this arrangement will be called as slant six cylinder engine.
- V6- In V6 arrangement, the engines are arranged in V-shape where each slant line in letter “V” represents a cylinder. Angle between the cylinders is generally 60 degrees.
- VR6- VR6 engines are V6 engines in which there is a narrow angle between cylinder banks.
- Flat six engine- This type of engine has a common crankshaft on which cylinders are placed in such a way that three cylinders lie on each side of the crankshaft. The cylinders are arranged in such a manner that BDC of one cylinder results in TDC of second cylinder.
Firing order of 6 cylinder engine
The need of firing order in engines arises due to many reasons. Firing order directly affects the efficiency of the engine hence, it is important to find an optimum firing order.
1-5-3-6-2-4 and 1-4-2-6-3-5 are most commonly used firing orders in six cylinder engines. In a four stroke cycle, two engines are idle and rest four perform one of the power producing strokes from the cycle. The firing of the spark plugs is timed in such way that cylinders fire only during ignition stroke.
If the firing order is not proper, the engine will fail well before its design life. Improper firing order results in excessive heat generation and high magnitude of vibrations. Even driving becomes cumbersome due to noise produced due to vibrations. It is recommended to use a proper firing order to avoid such problems.
What is the firing order for a V6 engine?
6 cylinder engines can work on both 2 stroke and 4 stroke cycles. We take an example of 4 stroke 6 cylinder engine in V6 configuration. Different cylinders perform different things simultaneously. Every stroke happens in a timely manner. The tasks that each cylinder performs in one power stroke are shown table below-
Crank rotation for 1 firing is given by the equation- 720/n
where, n is number of cylinders.
Lets take an example of a 4 stroke 6 cylinder engine whose firing order is 1-4-3-6-2-5. Following events take place inside the engine-
- In first 120 degrees, cylinder #1 fires.
- In next crank rotation (crank position 240 degrees), cylinder #1 moves towards exhaust stroke and cylinder #4 performs ignition stroke.
- In next crank rotation (crank position 360 degrees), cylinder #4 moves towards exhaust stroke and cylinder #3 performs ignition stroke.
- In next crank rotation (crank position 480 degrees), cylinder #3 moves towards exhaust stroke and cylinder #6 fires.
- In next crank rotation (crank position 600 degrees), cylinder #6 moves towards exhaust stroke and cylinder #2 performs ignition stroke.
- In next crank rotation (crank position 720 degrees), cylinder #2 moves toward exhaust stroke and cylinder #5 performs ignition stroke.
After this, cylinder #1 fires again repeating the entire cycle. This cycle continues to produce mechanical energy.
Vehicles using 6 cylinder engines- examples
Usually cars use 6 cylinder engines as per their requirements. Many companies prefer V6 engine for their cars.
Mercedes Benz M272-E35 uses a firing order of 1-4-3-6-2-5, which has powered ML350 and R350 vehicles. Other companies like Mitsubishi (6G7 engine). Nissan (VG engine) and Honda (C engine) also use six cylinder engines.
6 cylinder engines are also used for racing cars. Examples include engines like Alfa Romeo 155 V6 TI, Renault-Gordini CH1, Nissan GTP ZX-Turbo, Nissan NPT-90, Ferrari 126C etc.