I want to see if I have this correct if you advance or retard timing your talking about atdc correct. So lets say to retard atdc timing you increase btdc timing. I understand the event in stock terms I'm just a lil confused when it comes to any changes. Thanks for the help

 

Also lets say I use the 1 degree of time per pound of boost. Im running 5 pounds so I take out 5 degrees and stock honda timing is 16 atdc so that puts me at 21 degrees total. I dont think this theory would work for some thats running 20 pounds of boost because of the efficiency of our motors at higher rpms. Help me out just trying to understand.

 

a plug is never fired atdc (unless waste spark), that doesn't make any sense. everything would be btdc. you're looking at base timing as a set timing. go look at a map, there's different timing for all conditions.

 

if stock is 16* BTDC and you retard it 5*, you would be at 11* BTDC. when you retard the timing, it happens later, which makes it happen closer to TDC

But 16* BTDC is only at idle. As RPM and load go up, the timing advances(to a point). To as much as Mid 40's BTDC.

 

yeah i understand that a plugs fires right before it reaches tdc (the point where the air/fuel is ignited) and i wasnt really trying to relate it to anything on a map. i understand the timing moves for different events. i'm talk bacis physics like every action has a reaction. so u move btdc to a later event (retard) therefore the atdc event happens earlier (advance)



i think this is were im getting messed up. im thinking of a circle with the numbers going clock wise which would make what you wrote advanced because you made the compression stroke longer (by 5 degrees) because that would make it closer to 0 or tdc. i know im off somewhere.

i understand the more dense the air the less timing it needs (dense air burns faster). i'm jus confused on what side of the combustion event you actually pull from. so when you say i pull 5 degrees of timing does that mean i pulled from the before or after tdc

 

ok so i did some more research and i think i may have found my answer. because you dont want the spark plug to fire to early on the compression stroke working to push the piston back down before it can make it to the power stroke (aka detonation). you add (pull) timing to the atdc so that the event happens later in the power stroke???

maybe i need to walk away for a couple of hours to clear my head and start back later hahaha