Well, the increased backpressure causes a less effective exhaust stroke. It's pretty simple to visualize - the piston is pushing out exhaust with there being more resistance to the "push", so a little more stays in.. Anyway, yes, the dilution causes a slower flame front.

"How are you taking into account the speed of the engine, in combination with the presumed speed of the combustion to figure a given advance?"

I am researching, learning, and making guesses - I think at this point I can call them "educated guesses". As I acquire more knowledge, I formulate more and more ideas/plan-of-attacks, and then test as best I can.. It's a constant process.. I have the module loaded with the stock curve and a test curve - so with the handlebar switch, I can switch back and forth constantly as I test..

As I get more dyno data, there will be less guessing...

 

Taking a cue from RageHard..'s map, I added a "big front end" to my latest test map - I tempered it a bit due to my bikes' different mod combo.. I tested power, throttle response and power ramp-up from 2K while climbing a 75 yard run up a hill offroad. Sure enough, more power, throttle response, and power ramp-up.. Here it is. Clik on it to read the values.

 

What does the bottom most row in the attachment above represent? Can't quite make out the text or numbers.

 

The row I'm curious about is in the red box..

 

Ah, this is a screen shot of the ignition advance curve I tested today.. The program is called DashPro Jr.. Those are cells with advance values in them..

 

Ah, for a moment I thought we were looking at HP numbers!

 

Been following this thread. From the numbers, I believe we have the Euro version KLX here in Taiwan. Are euro timings similar to Aussie timings? From the service manual I get this:

(TH,EUR,SEA)BTDC10°@1300r/min(rpm)∼BTDC34°@11000r/min(rpm)

Any knowledge on the euro?

 

confirmed the euro numbers you listed (2009 klx 250s EU) owners manual i have with the bike i got

 

Hey fellas, this becomes important - Assuming the Aussie/Euro/USA bikes carry the same cams/cam timing, and compression ratio - The Aussie/Euro's will become over-advanced with a slipon and a performance AFR. I'm guessing over-advancement would become a performance issue if AFR@WOT reaches 13:1 or below.

 

Here is the 35° jump in power. The verticals are RPM - 8500 on left, then 9k, 9.5k, and 10k..Hp is the numbers on the right. All 3 curves are basic "flat line" curves. So all of them are static values after 5K.

Blue - 25°
Green - 35°
Red - 40°

This is an example of what happens when ignition timing becomes more optimal , when it over-advances to "stalemate", and finally, when it over-advances to power loss.

Also, while 35° did this, there could be more with a different value in this RPM area.