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
Honda Civic 2008. AC stopped working suddenly and engine check light came ON for a day.Next day AC worked and no engine light.
ANSWER : 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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An inconsistent starter motor that occasionally works perfectly now will not work. Then engine will not crank at all.
ANSWER : 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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I have a 96 Ford ranger with cel p0340 I have recently done a timing belt, engine runs great replaced cmp sensor cel still on
ANSWER : Hi There,
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.
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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Engine rattles when I I turn on my engine for the first time in the morning. It seems like it only does it when it’s cold
ANSWER : 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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Engine malfunction light, reduced engine power, engine powered down
ANSWER : Hi there. There are a lot of things that can cause this on your 2012 BMW M5. I usually start by scanning the computer for codes to see what comes up. If there are not codes then I load test the alternator and the battery to see if they are failing. Low voltage in the electrical system will cause this. If that is fine, then it is usually caused by a failing throttle body. I have seen a lot of these fail due to the motors in them hanging up. If the problem is only happening intermittently, this can make the issue hard to duplicate, but you can still have tests done on the car. If you are going to have this fixed, consider YourMechanic, as a certified mechanic can come to your home or office to test the vehicle and diagnose the Engine Malfunction Light.
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ANSWER : The problem you are describing likely stems from an intermittent electrical fault in the wiper circuit. The windshield wiper system uses a small electric motor to move the wiper arms that you see on the windshield. That electric motor is controlled through a switch, relay, fuse, and wiring. One, or more, of those electrical components has failed although it is also possible that the mechanical arms are binding (seized, if the lubricant has dried out) thus causing the electric circuit to the motor to overload. Regardless of the underlying fault, if you request a non functioning wiper diagnostic/repair, the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
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Car engine dies
ANSWER : The first thing I would do is have the turbo/intake system ’smoke’ tested or visually inspected for any leaks. Without a smoke machine, you could spray your engine and turbo system with brake cleaner and listen for idle changes to help determine if there is a leak. The brake cleaner method is not as effective as using a smoke machine.
Next, checking your fuel pressure is in order to see if you lose fuel pressure as it sits or if the fuel pump in the tank is weak. If the fuel pump in the tank is weak or losing pressure, it would cause the engine to crank as you mentioned. Performing a fuel pressure test is not easy and requires a special tool. If you want to have this looked at a technician from YourMechanic can come to your car’s location to diagnose your stalling issue.
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Just replaced head gasket, changed crack sensor new plugs. The check engine light is on, but dim, the only other light that the dash is a normal battery indicator. The fuel pump is not running when switch is turned on, the power windows don’t work, it turns over but not firing. It’s like only one part of the system is working. Also the heater fans work even if the switch is off.
ANSWER : I would first look at the diagnostic trouble codes. Those codes are available because the check engine light is on. If the fuel pump is not running (momentarily) at key on, that fault alone will prevent the car from starting as there will be no fuel pressure. Pump output and pressure can be directly tested and you can also check for electrical power to the pump. To find out why the engine will not run, the recommended diagnostic is a no start diagnostic. If you request that service, the responding certified mechanic will get this taken care of for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.
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