Engine Timing Explained Nicely

The timing of your engine is the difference between 24MPG and your engine being in multiple pieces. Let's dive in.

UNDERSTANDING THE ENGINE

To grasp the concept of engine timing, it’s essential to have a basic understanding of how an engine works. For example, in a 4-cylinder engine, you have four pistons, four spark plugs, four fuel injectors, and one crankshaft. The pistons are connected to rods that rotate on the crankshaft, moving up and down within the cylinders.

During the upward movement, fuel is sprayed into the cylinder. As the piston rises, it compresses the fuel mixture. The spark plug then ignites this mixture, causing an explosion that forces the piston downward. This process is continuous, allowing the engine to run smoothly.

WHAT IS TIMING?

Regardless of the make or model of the car, some component, whether it’s a computer or a distributor, determines when the spark plug should fire. This timing is critical: if it’s incorrect, the fuel may not ignite at the right moment, or it could ignite too early, which places excessive stress on the piston.

In addition, cars are equipped with camshafts that control the opening and closing of the intake and exhaust valves. These valves are positioned at the top of the cylinder, out of the piston’s way. During the piston's downward movement, the intake valves open to allow air in, while the exhaust valves allow exhaust gases to exit. The camshafts are connected to the crankshaft via gears, which are connected via chains or belts.

If the timing is off, the valves may interfere with the pistons, leading to a collision that can cause severe engine damage. If the timing is significantly incorrect, this collision can occur multiple times per second across several cylinders, resulting in catastrophic damage to the engine.

WHAT ARE THE DEGREES?

The "degrees" are almost always defined by Cylinder 1; and the rotation of the crankshaft. When cylinder 1 reaches Top Dead Center on the stroke,