Can someone explain TIMING to me please

[axisT6]

I have always believed that timing was spark in relation to where the piston is. For example if you get spark at TDC, the timing would be 0*. I keep hearing things about if you advance timing you may have to run a higher octane fuel and what not. Or I hear some say, "my truck seems to run better when I advance the timing 4* etc.". If someone could explain this, I would be very thankful.

[Mark in INdiana]

In extremely simplistic terms, advancing the timing so the spark occures before TDC gets the mixture expanding so it can exert the optimum force to move the piston down in the bore. This optimum setting is usually just before detonation (pinging). Increasing the advance beyond this optimum setting sets up even higher pressure conditions that cause detonation to occur. This can be countered with higher octane fuels or booster additives that increase the fuels resistance to detonation. With higher octane you could run a bit more timing advance before you run into detonation again.

[axisT6]

Spark before TDC? How does that work? Are you saying that spark occurs before TDC on the compression stroke? Wouldn't spark occur a hair after TDC on the compression stroke?

[Bob T]

The combustion of the air/fuel mix takes (a very small) time. It is a combustion process, not an explosion. The spark advance gets the combustion started before TDC so the flame front gets time to develop before the piston gets to TDC. It's kinda like in baseball you start swinging the bat before the ball gets over the plate, so the bat & ball get there at the same time.

[4x4bowtie]

It's kinda like in baseball you start swinging the bat before the ball gets over the plate, so the bat & ball get there at the same time.

good one, i like that.

[axisT6]

Ok,

There is a sticker under the hood of my truck that says timing is 0*. With that said, where is the piston on the compression stroke when the spark occurs?

[axisT6]

OK, I got my question answered here http://auto.howstuffworks.com/ignition-system1.htm

[InProgressC1500]

good one, i like that.

yeah, i like that, that's one of the best ways i've heard to simplify it. I'm gonna have to remember that