i've tuned a lot of piston cars using the AEM EMS. the thing that's confusing me is the trailing/leading spark (ignition timing). on a piston engine you retard the timing under boost to prevent knock. usually if you have high octane fuel and a properly matched engine compression ratio, you advance the timing to achieve MBT, and then retard the timing a couple degrees from there for safety since fuel isn't always perfect.


can someone explain the leading and trailing spark to me? is the time that separates the firing of a spark from the leading and trailing plugs constant and you when you "retard" the timing, are you firing the both leading and trailing plugs earlier by a specified amount?

thanks!

 

Are you asking about the ecu's ability to handle the trailing or are you asking for a primer on trailing/leading ignition outside of any ems?

 

im asking for both, how they work outside of any ems and if they do need to be controlled individually, how does the aem ems do that? there's only one load vs ign table

 

There is one load vs rpm ignition table and a load vs rpm split / difference table. So 2 different tables. So leading timing is defined by the first and the trailing is figured from the 2nd table. ignL +/- split = ignT

Here is a quick and simple explanation of Rotary timing and ignition.
http://www.rotaryengineillustrated.c...-ignition.html