Advancing Your Timing

[troyminator]

Guys,

 

I have searched on the forums and I haven't been able to find the exacts behind advanced timing.

 

I have read about how to do it (either modifying your own plate or purchasing plates).

 

Could somebody explain the mechanics/purpose?

 

Thanks

 

T

[Dextreme]

Basically what happens is that the spark ignites the air/fuel mix sooner (prior to the piston reaching TDC) utilitzing more of the internal explosion (combustion) which creates more power.

[troyminator]

Thanks Dextreme,

 

A little more question with that answer...

 

...(prior to the piston reaching TDC) utilitzing more of the internal explosion (combustion)

 

I am just thinking outloud... When the pison is traveling up...there are forces required to continue moving up...so if you "spark" prior to reaching TDC, then there will be even more force required to finish the compression stroke. I assume that we are talking about millisecs prior to hitting TDC, but still I don't understand how that adds more power.

 

I guess the main problem I am having is understanding what you mean by

 

...utilitzing more of the internal explosion

 

Thanks again as your input is greatly appreciated!

 

T

[Banchetta]

Your thinking that the stock spark fires exactly at tdc, but its not like that.....there is a delay from when the flywheel makes contact and the time that the spark actually reaches tdc....also you have to remember that this motor is turning almost 10Krpms....thats almost 166 revolutions per second....just think about that for a second....then you also have to consider the timing delay of the explosion...just because it sparks at tdc, you have a timing delay of spark, explosion, and actualy force pushing the piston back down....hope that helps

[troyminator]

Banchetta,

 

Thanks that helps allot. So basically, stock isn't firing at TDC...and potentially after TDC when it is already moving down. So the goal of the timing plate is to change the spark timing to fire prior to reaching TDC...therefore explosion occurs as close to TDC as possible, hence increasing the force/acceleration of the piston on its way down.

 

So based on this, how do you know how much to advance the timing? Is it a trial/error endevor in which you listen to the engine and look at the plug for some signs?

 

Thanks again!

 

T

[Dextreme]

Most people start of with +4 advance.

 

...utilitzing more of the internal explosion

 

What I mean is that you get a "longer burn time" before the gas exit the exhaust ports...so more of the fuel/air is burned.

[troyminator]

Dextreme,

 

Thanks for the advice.

 

One last question (I think )...if I start with a 4degree advance, how will I know if I need to decrease/increase the advance?

 

OK...one more question....are there any downsides to doing this modification?

 

Thanks,

T

[Dextreme]

If you go with +4, I don't think you will desire to go more or less (unless you get your jugs drag ported).

 

The downside is that you want to make sure you use at least 92-93 octane and that the gas is fresh. I wouldn't use gas that has been sitting over 2 months.

 

 

Oh, and seeing that you are tearing down your motor...I would suggesting getting your crank welded if it is not.

[Banchetta]

Agreed, go w/ +4 unless you have drag port and running 100+ octane fuel....I dynoed mine and found +4 to be the best and lost hp at +7...list of my mods on the bottom..