Ignition timing is crucial for a well-performing engine. If your ignition timing goes off, it could lead to serious engine damage.
But what is ignition timing, and how does it work?
Also, is there a way to fine-tune it?
We’ll answer these questions and share tips for optimizing your driving experience.
This Article Contains:
- What Is Ignition Timing?
- Ignition Advance Vs. Ignition Retard: What’s the Difference?
- 4 Tell-Tale Signs Your Ignition Timing Is Off
- How to Fine-Tune the Ignition Spark Timing
- 5 Ignition Timing-Related FAQs
What Is Ignition Timing?
Ignition or spark timing controls the firing of your spark plug during the compression stroke in an internal combustion engine. Proper ignition timing ensures that your engine functions at peak efficiency.
Let’s break down the process.
In a four-stroke engine, each ignition cycle has two up and two down strokes, creating two crankshaft revolutions.
1. Intake stroke-down: This stroke goes down and draws in the air-fuel mixture.
2. Compression stroke-up: Here, the piston position moves up, maximizing air compression at the top of the stroke, known as the Top Dead Center (TDC). It marks the highest piston position.
This is where ignition timing does its work.
The fuel needs to explode with maximum power. So, the spark must arrive slightly before the piston reaches the top since it takes some time for the fuel’s explosive flame to propagate.
When the air-fuel mixture ignites in the combustion chamber, pressure is built in the cylinder as the burning gasses expand. Then, pressure maximizes just as the piston hits the Top Dead Center.
3. Power stroke-down: Once spark ignition occurs, the explosive pressure drives the piston down as hard as possible.
4. Exhaust stroke-up: As the piston moves up, the exhaust gas is driven from the cylinder, ready for the whole process to start again.
While the spark’s timing is crucial to maintaining high engine performance, a range of factors can influence this timing:
Any changes or upgrades to your engine will also require an ignition timing adjustment — advancing and retarding.
Let’s find out what these terms mean.
Ignition Advance Vs. Ignition Retard: What’s the Difference?
In mechanical ignition systems, we manually measure the ignition timing by noting the degrees a crankshaft turns before the piston reaches the TDC. And when the spark plugs should fire can be achieved by advancing or retarding the timing.
Here’s a breakdown of each term:
1. Timing Advance
Timing advance means firing the spark plugs earlier in the compression stroke. The ignition advance angle is usually specified in degrees Before Top Dead Center (BTDC), indicating the number of degrees before the piston reaches the top of its compression stroke when the spark plug should ignite the air-fuel mixture.
Advance is required because the air-fuel mixture in the combustion chamber doesn’t burn immediately, and it takes time for the flame (spark plug fire) to ignite the mixture.
The advance helps get the spark past the ignition delay, increasing your engine’s horsepower and peak torque.
2. Retard Timing
Retard ignition timing causes your spark plug to fire After Top Dead Center (ATDC) in the compression stroke. Retarding ignition timing reduces engine detonation — known as pre-ignition or engine knocking. It’s when the fuel ignites incorrectly, causing unexpected pressure and noise.
Engines running at higher pressure levels, like turbocharged or supercharged engines, benefit from retarding the timing of an engine. Retard timing on these engines helps compensate for denser air-fuel mixtures, allowing them to run better.
But when do you need to adjust this timing?
Let’s explore the indicators that suggest your ignition timing needs attention.
4 Tell-Tale Signs Your Ignition Timing Is Off
Several performance issues can occur if the timing of your ignition system is awry.
Here’s what to watch for:
1. Engine Knocking
If the spark plug fire is too advanced to the piston position, the rapid air-fuel mixture combustion can push against the rising piston during compression. In severe cases, the advanced ignition spark results in engine knocking.
Engine knocking can also happen when combustion occurs within the cylinder after the spark plug fires.
If the air-fuel mixture ignites too soon during combustion, the heat generated will increase, potentially leading to serious engine damage.
3. Low Power
If the spark occurs too late to the piston position, the peak cylinder pressure — the highest force created when fuel burns, will be delayed. Missing the window for peak cylinder pressure results in lost power, high emissions, and unburned fuel.
4. Decreased Fuel Economy
The ignition spark’s timing is essential because if it’s delayed or too fast, the entire combustion process is off. Your engine will compensate for the reduced power by using more fuel, reducing the fuel economy.
If your ignition spark timing is off, it needs immediate fixing. Let’s explore how it’s done.
How to Fine-Tune the Ignition Spark Timing
Fine-tuning the ignition timing requires knowledge, caution, and proper tools, like the timing tape, timing light, etc. That’s why this is best left to a mechanic.
Here’s how a mechanic will fix the timing:
- Locate the timing mark (an indicator for setting the ignition timing) on the crank pulley. A mechanic will use a timing light to illuminate each timing mark on your crankshaft pulley (as with most cars or modern engines) or flywheel.
- Identify a stationary notch (a reference point) indicating the current base timing as the engine operates.
- Refer to your vehicle manual for the correct spark plug gap and idle speed to adjust the base ignition timing properly.
- Start the engine and engage the parking brake, then let it idle for about 15 minutes to reach its normal operating temperature.
- Connect the timing light. Keep the timing light leads away from spinning engine components like fans and belts to avoid engine damage.
- If you have a distributor with a vacuum advance, ensure the hose is disconnected and plugged.
- Shine the timing light on the timing marks on your crankshaft pulley, and as the light pulses, they’ll see the stationary line pointing to the current degree mark. They’ll then adjust the timing base accordingly.
- Turn off the engine and put everything back in its place.
Have some more ignition-related questions?
5 Ignition Timing-Related FAQs
Here are the answers to a few queries regarding ignition timing and systems:
1. What Is Engine Timing?
Two kinds of engine timing take place in every engine. There’s camshaft timing (valve timing) and ignition timing (spark timing).
Cam timing manages valve opening and closing. Ignition timing manages when the spark plug fires. These different actions must be timed together to make the engine work efficiently.
2. What Is Initial Timing?
Initial timing is the ignition timing applied to the engine at idle and is set by the position of the bolted-down distributor (a component that carries high-voltage electricity from the ignition coil to the spark plugs).
3. What Is Static Timing?
Static timing is a method for setting your ignition timing and occurs when you set your ignition timing with your engine off.
You can do it by setting the crankshaft at the correct number of degrees before TDC. Then, adjust the distributor by turning it till the contact-breaker points are opening slightly.
The amount of total timing required determines the initial timing. The proper setting will also depend on the amount of mechanical advance your distributor provides.
However, this timing method doesn’t consider wear between two parts, such as the teeth of gears.
4. Are There Different Types of Ignition Systems?
Yes. They include:
A. Mechanical Ignition Systems
This ignition system uses a mechanical spark distributor to carry a high-voltage current to the correct spark plug on time.
When setting an initial timing advance or retard, the engine should be idle, and the distributor shaft should be adjusted to achieve the best ignition timing for the engine at idle speed.
B. Electronic Ignition Systems
Newer engines typically use computerized ignition systems (electronic ignition). The computer has a timing map containing spark advance values for every engine speed and engine load combination.
Note: The engine speed and engine load will determine how much total advance is needed.
The computer signals the ignition coil to fire the spark plug at the indicated time. Most original equipment manufacturers’ (OEM) computers can’t be modified, so you can’t change the timing advance curve.
5. How Is Ignition Timing Controlled?
In most modern engines, the computer handles ignition timing control.
However, engines with a distributor can deal with ignition timing control in many ways:
A. Mechanical Advance
With mechanical advance, as engine revolutions per second (RPM) increases, it uses centrifugal force to push weights outward. The weight’s movement rotates the trigger mechanism, which causes the ignition to be triggered sooner.
B. Vacuum Timing Advance
With vacuum advance, as the engine vacuum rises, it pulls the diaphragm inside your vacuum canister. Since the diaphragm is connected to the advance plate (part of the distributor) by a linkage, its movement rotates the trigger mechanism. The vacuum timing advance causes the ignition to be triggered early, enhancing engine torque.
C. Computer-Controlled Compatible Distributors
In these systems, the ECU controls the timing and the ignition coil. The distributor sends an alert from its internal pickup module, camshaft, or crankshaft sensor to the ECU. The ECU then sends a signal to the coil, telling it to fire. Current travels from the coil to the distributor cap and its rotor and a spark is routed to the spark plug.
Correct Your Ignition Timing for Peak Engine Performance
Optimal ignition timing is vital for achieving peak torque and horsepower and enjoying a smooth driving experience.
However, any misstep while adjusting this ignition timing can lead to serious engine damage. So it’s best to have your car regularly serviced by professionals like AutoNation Mobile Service.
We’re a mobile auto repair service that offers upfront pricing and a 12,000-mile/12-month warranty on all repairs.
Contact us today for services and repairs carried out straight from your driveway.