How Does Engine Timing Work?
How does engine timing work?
Experienced mechanics share their insights in answering this question :
Engine timing is actually a closely coordinated dance between valve timing, injector timing, and spark timing.
Valve timing is the control of opening and closing the intake and exhaust valves in synchronization with the up / down movement of the pistons. This ensures that air and fuel get into the combustion chambers, the fuel burns at the proper time, the exhaust gases are expelled from the cylinders, and the cycle begins again.
Fuel injection timing is spraying fuel into the intake air stream or combustion chamber while the cylinders are on their intake strokes.
Spark timing is igniting the air/fuel charge at the right time so that the most usable power is created and the least amount of emissions exit the engine.
When you combine all three of these systems together – pistons moving up and down, intake valves opening and closing allowing air and fuel to enter the cylinders, spark plugs igniting the air/fuel mixtures, and exhaust valves opening and closing allowing exhaust gases to exit the cylinders, you have the total effect of engine timing.
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The engine timing system synchronises the motion of the crankshaft and the camshafts. This in turn operates the valves in time with the pistons, making sure the pistons and the valves do not come into contact with each other. In some cases the engine timing system also drives the fuel injection pump and water pump.
Timing belts – aka cambelts – are timing chains for engines with larger bores and strokes. They play a significant role in how internal combustion engines work. They harmonize camshaft and crankshaft rotation, and if both of these are in sync, the valves and pistons will operate correctly.
There are two kinds of timing, cam timing and ignition timing. The cam timing regulates the valves and pistons, and the whole process is controlled by the timing chain or belt.
A timing belt, which is also known as a timing chain or cambelt, is a toothed belt which keeps the top half of the engine (the cylinder head and valves) aligned and synchronised with the crankshaft and pistons in the bottom of the engine. This then allows the values and pistons to move in harmony with each other.
As the crankshaft turns, it sets the timing belt in motion. The timing belt then turns the camshaft and opens or closes each valve and allows the pistons to move up and down.
When the timing belt breaks, the crankshaft will continue to spin, while the camshaft will stop turning. As a result, the pistons will continue to rise and fall in their cylinders and can, in some instances strike the valves.
As a unit, it also contains main three components known as cam shaft, timing chain and crank shaft. The same is illustrated in the figure. The main functions of the timing mechanism include operating the inlet valve, introducing a spark and operating the outlet valve.
The name timing belt comes from the fact that the belt is responsible for the synchronized movement of the camshaft and the pistons. If the timing belt doesn`t keep the camshaft valves open and closed in parallel order with the camshaft, then the whole engine can fail.
Most timing belts are located under the bonnet, usually either on the left or right of the transmission. You may need to remove the engine mount to access the timing belt. It will also probably be protected by a plastic cover.
Don`t get confused—a serpentine belt is not the same thing as a timing belt. The serpentine belt and timing belt have very different functions in your vehicle. The timing belt is located inside the engine and keeps the crankshaft and camshaft in sync.
Not all cars have a timing belt, some cars have timing chains which do the same job as a belt. The timing chain does not require regular scheduled replacement, whereas timing belts need replacement every so often depending on your vehicles manufacture specifications and vehicle application.
Where a quiet, more efficient engine is required, a timing belt is often preferred. As they are made from rubber, they`re also cheaper to manufacture, which means that car manufacturers may choose to build them into the vehicle.
Belts are quieter and because of their material, less expensive to produce. Timing chains are housed within the engine and receive lubrication from engine oil and can last a long time, while timing belts are located outside of the engine and tend to dry out and crack.
Ignition timing (or spark timing) controls when the spark plug fires during the Compression Stroke. Ignition timing is measured in degrees of crankshaft rotation, before top dead center (BTDC).
Currently, we recognize four types of ignition systems used in most cars and trucks: conventional breaker-point ignitions, high energy (electronic) ignitions, distributor-less (waste spark) ignition and coil-on-plug ignitions.
Ignition timing fully under the control of the engine management system with spark timing determined by the throttle position, engine speed, knock sensor, engine temperature, and manifold vacuum.
TIMING ADVANCEAs engine rpm increases, it is necessary to advance the ignition timing. If not, the burning process in the combustion chamber would take longer than the speeding piston would permit, resulting in an incomplete burn.
Relevant Questions and Answers :
the most relevant questions and answers related to your specific issue
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Hi there. In both cases, when an AC system is not working and a warning light is coming on the dashboard, typically a professional mechanic will complete the same initial inspection, which is to download the stored error codes that triggered the warning light initially. This tends to give them an idea as to what is causing the problems. This could be something as simple as an electrical relay that is faulty or loose or an indication of a computer related "glitch". Either way, the best way to move forward is to have a professional mobile mechanic complete a check engine light inspection.
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Hi there. It is possible for the starter to fail. But before replacing the starter, make sure that the battery cables are tight and clean. Then check the starter relay and make sure that the relay is clicking. If the relay is not clicking, then check for power to the relay. If there is power to the relay but there is no click, then the starter relay would need to be replaced. If there is no power to the relay, then either the wiring from the relay to the ignition switch has a break in it or the ignition switch is failing. If there is power to the relay and power to the starter motor, then the starter motor needs replaced. If you need further assistance with your no start issue, then seek out a professional, such as one from Your Mechanic, to help you.
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This may happen for a couple of reasons. First, check to be sure that the connections to the sensor are clean and not faulty or broken. Secondly, check to be sure you replaced the correct sensor as there are two camshaft position sensors in some applications. If you need further help with this, please reach out to us here at YourMechanic as we are always here to help.
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Hello. Most likely, the noise you describe is coming from one or both of the camshaft phasers on your engine. These devices which are operated by engine oil pressure, vary camshaft timing (relative to the crankshaft), enhancing engine performance and fuel economy. Since these devices are operated by engine oil pressure, when the engine is off overnight, engine oil drains out of them, and it take the first few seconds of engine operation to refill them when you first start the engine each day. For those few seconds, a metallic rattle can be heard as you have experienced. While not immediately threatening, they should be replaced when the timing chain service is done on your engine.
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