purpose of 2*

Eddge · 02-29-2008, 10:35 PM

What exactly does the 2* advance do? I understand its done for more power. However, I get pretty good gas mileage out of my stock 07. i havent done anything to modify performance yet. how much power does it give?

titaninak · 02-29-2008, 10:44 PM

i dont think any gains can be measured other than the Butt dyno, you will notice alittle more get up an go.... i am sure others will chime in on this one.
BTW- thanks for serving- my son just got back from afghanistan last saturday.

**anmut** · 03-01-2008, 05:41 AM

+1 for your military service. Folks like you make it possible for me to sit here, free as a bird. Thank you.

2* advance adds just a bit more gas from what many consider a lean mix from the factory. In stock form it's worth just a little on the butt dyno but everyone raves after you swap out the exhaust and add a CAI.

Nuke · 03-01-2008, 07:19 AM

Thank you for your service to our country.

It doesn't change the mixture. Just the spark timing.

Advanced means the spark will happen earlier. Retarded means it will happen later. Two degrees is the amount of crankshaft rotation. So, if the spark normally occurred 15 degrees before top dead center at idle, it would occur at 17 degrees before top dead center with the 2* timing advance.

The reason it has to occur before top dead center is because it takes time for the fuel to burn, so the spark only starts the process, then the flame has to propogate throughout the combustion chamber. As it does, the gasses produced expand and pressure rises.

For maximum power and the most complete combustion, you want to advance the timing as far as possible. But if you advance it too far, then the pressure will reach maximum too early, maybe even before the piston reaches top dead center. That's a bad thing. Very bad. It's called KNOCK.

The timing is not constant. It advances as the engine speed increases, because you have to start the fire earlier to keep up with the piston. It also advances under load.

I'm not sure the explaination is 100% correct, but there are a lot of experts on here to correct me if I misspoke.