timing

[carpenter]

hey i just bought a rpm timing plate how do i know to retard it or advance it?

[GOTFEAR]

i believe moving it up advances the timing and go down is retarding the timing

[wilkin250r]

Are you asking which direction does which, or are you asking the more general question of WHY and WHEN you want to alter your timing, and effects it will have?

[carpenter]

wat does retarding it do and wat does advancing it do??

[wilkin250r]

First off, advancing your ignition too far can lead to detonation, which can destroy your piston rather quickly. I recommend a google search for "detonation" if you don't know what that is.

But let's assume you don't take it that far.

As a general rule, advancing the timing will give you a little better hit in the midrange (because you get a better flame front travel), but causes it to fall flat in the higher rpms.

Retarding the timing is exactly the opposite, it decreases the power hit, giving you a little smoother powerband, and allows the engine to rev out a little more.

[All250R]

The basic idea behind ignition timing is to make peak cylinder pressure during the burn happen at the best crank rotation degree so the most heat energy is spent making the most mechanical energy.

Combustion chambers that are polluted with exhaust gases from pipe and porting configuration particularly will require more advance in that area of the rpm range because the flame is going to have more trouble getting the fuel burnt efficiently. Typically as the engine becomes more in tune, less timing is required so the more efficient burn is not creating extensive negative work against the rising piston.

So which timing map is "better"? You can probably gather that it depends on how the engine is configured. The "best" "updated technology" 4stroke ignition map is not going to work well in a drag ported 2stroke. CR ignitions are a common upgrade, but to say it is "better" implies that you know what the timing map is and how it matches a particular engine. Otherwise, we're really just speculating or staring at the dyno hoping for a better result. Your timing plate is a similar situation. You're going to need to play with it ideally on a dyno to see where the engine makes best and hopefully reliable power for your setup, otherwise you probably didn't understand completely what you were buying.