There are two kinds of timing, camshaft and ignition timing.
Knowing the difference between them and what they do is very important.
Timing is different on every engine, so it’s a good idea to have a good service manual, before attempting any work.
This has everything to do with, making sure, the valves are out of the way; when that piston comes flying, toward the cylinder head. Because, in some engines, the piston can actually, impact a valve, at the top of its stroke. In these engines, called “interference” type engines, even a slight slip, can be catastrophic. That’s why, it’s so important to inspect your timing belt, for wear or damage.
So, it only job is to determine, when the spark plug should fire.
Most engines like the spark plug to ignite, anywhere from 32 to 38 degrees, before top dead center (BTDC), or in other words; before the piston has compressed the fuel & air all the way to the top. Usually the magic number is between 34 and 36 degrees, but every engine is different.
Ignition timing, can be throw off by, any number of things. Newer engines adjust themselves, so as long as your sensors are all functioning, as they should.
Above all, an important process, when it comes to running an engine. If the spark plug fires too soon or too late; during the compression stroke, damage to the engine can occur.
Ignition timing, comes into play, during the compression stroke of the engine. Furthermore, it controls when the spark plug fires during this process.
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