Stupid question of the day: what exactly does advancing the timing do?

[N8Miller]

As i was explaining to my fiance why i need my timing light back so that i can set it to 10* so that i can install my PMS, she asked "what exactly does adding or taking away timing do?"
So there it is, for the first time in 3 years, i dont have a car answer for her.

look at my post count, all those posts arent from "which exhaust sounds better" or "3.73s or 4.10s"... im no dummy, but what does it do?

 

[speadfreak]

Its the point at which the plug fires during the piston stroke. Like...lets say your timing is set to 10* BTDC. This means that your plug will fire 10* (out of 360*of crankshaft rotation) before the piston is at top dead center. If you were to advance it to 12*, the plug would fire 2* sooner (before to dead center). If your timing is too far advanced, the plug will light off the combustion too soon and actually try to push the piston back down before it has reached the top of its stroke.....this is where higher octane fuels come into play.....the higher the ocatane level, the slower it burns. More advanced timing usually means more power. Superchargers compress air, when you compress air it gets hot...the hotter the air, the more easily the combustion occurs, this is why when supercharging you must retard timing or "take timing out" This is also why high compression race engines need high octane race fuel....high compression=high heat....needs slower burning fuel. hope this helps
I'm not real good at explaining things....somebody else will jump in here i'm sure.

 

[jrichker]

The combustion process takes a finite amount of time to complete. That time varies very little in an engine, no matter what you do other than add another spark plug.

There is a fixed amount of time in milliseconds needed to burn all the fuel. As the crankshaft turns faster, the combustion process must start sooner to complete. That makes it necessary to advance the timing. It is desirable for all the combustion to be complete before the exhaust valve opens. This makes the engine to run at maximum efficiency

 

[speadfreak]

The combustion process takes a finite amount of time to complete. That time varies very little in an engine, no matter what you do other than add another spark plug.

There is a fixed amount of time in milliseconds needed to burn all the fuel. As the crankshaft turns faster, the combustion process must start sooner to complete. That makes it necessary to advance the timing. It is desireable for all the combustion to be complete before the exhaust valve opens. This makes the engine to run at maximum efficency.

Ok...now "I" am confused. Did I explain it wrong to him?

 

[poneypower89]

suscribing

 

[89Notch]

You explained it right, what he is referring to I think is as the RPM's increase, the amount of time it takes to combust doesn't... but because the engine is spinning faster the same amount of time is a larger angle value. Therefore as you increase the RPM the timing needs to be larger as well.

 

[jrichker]

You explained it right, what he is referring to I think is as the RPM's increase, the amount of time it takes to combust doesn't... but because the engine is spinning faster the same amount of time is a larger angle value. Therefore as you increase the RPM the timing needs to be larger as well.

Vey good. I am glad someone understood my explaination.

 

[Euphoric306]

jrichker was explaining why the computer advances timing as rpm's increase (or vacuum or centrifugal forces do it on the pre-EECIV cars)

i think the original poster was asking about setting base timing though (he mentioned a timing light )