Ques. about main spark advance vs. rpm vs.map

I was adding 3* of timing on my first tune with tunercat and was looking at the above metioned table and I noticed that as you got closer to WOT the spark advance decreased. Now if I'm reading and understanding right the higher the KPA number the closer to WOT you are. I always thought that the higher the rpm the more spark advance you needed. I'm not seeing that looking at the table. Am I just not reading this right?

the higher the RPM the LESS timing you need. 100KPA would be WOT

WOT isnt determined by KPA... its determined by having greater than 70%+/- throttle.

the higher the RPM the LESS timing you need. 100KPA would be WOT

Could you explain this to me? I thought that at higher rpms the plugs need to fire sooner than at lower rpms to get the proper combustion

As far as WOT, sorry for the confusion I meant closer to full throttle

If you are thinking about the way a distributor works, you are correct. Timing advances with RPM because of the advance weights/springs. Typically, you want maximum advance at 2800 to 3000 RPM. The mechanical advance is then fixed beyond that RMP.

Now, you have to consider the Vacuum advance piece of it. At low loads, vacuum is high and the vacuum mechanism adds timing (ususally 20 degrees or so max, but it can be variable with an aftermarket canister). If loads increases, vacuum drops and timing is retarded.

In a computer controlled vehicle, all of this is done in the timing table. The Mechanical advance piece is the RPM axis and the Vacuum advance is the KPA axis. For a given RPM value you will see a timing decrease as load increases.

The reason you need to retard the timing at higher loads is to prevent detonation. That's why nitrous/forced induction motors need some retard programmed in or some other means to control detonation.

WOT isnt determined by KPA... its determined by having greater than 70%+/- throttle.

lets not get technical here. I answered the question he had.


and WOT is greater than 66% throttle according to STOCK tuning.... :rolleyes:

Thanks everyone.

I was told that you can add about 5* of advance across the board with big cams. Would my 3* be a good place to start with a 236/242 .556"/.576" cam and just see what she'll take?

lets not get technical here. I answered the question he had.


and WOT is greater than 66% throttle according to STOCK tuning.... :rolleyes:


well now if we want to get technical it depend on what rpm you are at and how far you puch the pedal. if your at 4000 rpms all you have to is push the pedal enough for 37.9 % throtle, but lets not get technical :D

well now if we want to get technical it depend on what rpm you are at and how far you puch the pedal. if your at 4000 rpms all you have to is push the pedal enough for 37.9 % throtle, but lets not get technical :D


ROFL !!! you got me with my own medicine !!! hhaahahaha :bow: