you tune your car to have different timing in a senarios with many variables such octane, boost pressure, rpm and so on. i understand how moving the distributor physicly will advance or retard your timing but how does the program do it? is it a special distriutor or is it the same technology as any old v8 dizzy? how does it work?

 

i need to know too. timing scares me

 

Let me take a shot at this. When people talk about ignition timing you often hear them say something like, I had 20deg. at xx load(kpa, psi). What they are saing is that the crank angle is 20deg. before top dead center.

You have sensors on your engine that monitor the engine speed and crank angle. So when a tuner makes an ignition map they are telling that they want to fire the ignition at 20deg. before top dead center(TDC) or what ever value they want at what ever load. When our computer has decided to fire the spark plug at a certain amount of time before TDC, called ignition advance, it then sends a signal to the ignition coil (internal or external) or ignitor. The coil, or inductor, releases a charge to the spark plug. I think an inductor(coil) is an eletrical componet that is able to build a charge and the computer tells it when to release that charge to the spark plug.

I am sure people can explain it better than I did.

 

Inside the CPU, there are timers - think of them like a stopwatch. They are reset/set and allowed to count for various lengths of time and do so based on the sensors inside the distributor. Those sensors coordinate all fueling and timing efforts - they synchronize everything concerning fuel and timing.

So in simple terms, the timer gets a synch pulse which resets it, is then allowed to count for some length of time (this time = spark advance), when time reaches 0, fire the igntor.

The three sensors inside the distributor are the:

CYL (#1 cylinder) - generates 1 pulse when cylinder #1 reaches TDC.
TDC (top ded center) - generates 4 pulses - one for each cylinder passing through TDC.
CKP (crank position) - generates a lot of pulses.

 

This may be a silly question but, how come the spark plug is sparked 20 degrees BTDC and not say.... 0 at TDC? In my mind, I'm thinking, the piston is going up and still hasn't reached TDC and now there is another force (The explosion) going against the piston going up. Get what I'm saying?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EE_Chris &raquo;</TD></TR><TR><TD CLASS="quote">Inside the CPU, there are timers - think of them like a stopwatch. They are reset/set and allowed to count for various lengths of time and do so based on the sensors inside the distributor. Those sensors coordinate all fueling and timing efforts - they synchronize everything concerning fuel and timing.

So in simple terms, the timer gets a synch pulse which resets it, is then allowed to count for some length of time (this time = spark advance), when time reaches 0, fire the igntor.

The three sensors inside the distributor are the:

CYL (#1 cylinder) - generates 1 pulse when cylinder #1 reaches TDC.
TDC (top ded center) - generates 4 pulses - one for each cylinder passing through TDC.
CKP (crank position) - generates a lot of pulses.</TD></TR></TABLE>
I knew I could count on you to save the day.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BG Boost &raquo;</TD></TR><TR><TD CLASS="quote">This may be a silly question but, how come the spark plug is sparked 20 degrees BTDC and not say.... 0 at TDC? In my mind, I'm thinking, the piston is going up and still hasn't reached TDC and now there is another force (The explosion) going against the piston going up. Get what I'm saying?</TD></TR></TABLE>

Because the engine is spinning fast as ****, and it takes time for
1)the signal to actually cause the spark
2)the spark to actually Ignite the gasses.

These two delays become a big problem as the motor moves faster and faster, so you must adjust the spark time accordingly. There are other factors, such as engine effeciency, and whatnot, but these are the major factors.