Been thinking about it - beyond the testing sessions.. I'm quite sure that since installing the Paray CDI, I haven't had ANY occurrences of high RPM ignition cutout/missed spark....

I will certainly be alert to any such anomaly from now on - and report findings..

 

Perhaps I should clarify the tiny amounts of time I'm dealing with. To get "real time" with any of my measurements, divide by 4.

For instance, due to the refresh rate of the KLX digital tach, It is possible (but doesn't actually happen, best I can tell) that a given measurement could be as much as +- .06 second in error. This is +-.06 on a 120fps video. In real time, this is +-.015 seconds!

 

Excuse not reading all the posts if this has been discussed. At any given rpm / throttle setting the cylinder has a variable amount of compression. For example low rpm/wide open throttle creates high pressures (why they can ping) so less advance is needed to achieve peak pressures at the atdc optimum rod angularity. Back the throttle off pressure goes down and more advance is needed. If the motor is modded it will fill more efficiently if the cam timing and pipe are working together. You might be trapping over 250cc into a 250cc jug, or at least more than stock. Compression is higher so LESS advance is needed not more at full throttle high rpms. Couple things with the klx, it's got a cv carb so wfo doesn't mean wfo, so the compression rise (and required timing) isn't so predictable or linear. It doesn't have a tps so any kind of map will have to be a compromise. Tuned for a wfo level ground run, or something else. Kudo's for trying though. fYI the rod is 107mm if you want to software the peak leverage on the stroke. Gas formulations are so iffy now flame speed and pressure rise calcs are real hard to predict.

 

The piece of the puzzle you didn't mention is engine loading. Loading affects how much advance can be tolerated at any given RPM. I'm testing at "normal riding loadings". For instance: I'll putt putt onto a steep hill in 1st@2kRPM and snap WOT when the bike is just fully on the hills' "ramp".. This is to test the curve from 2k-5k.. My WOT tests are on level ground, hold 4k in 3rd, snap WOT and start measuring at 5K.. In this manner, I hope to get the best "real world" power increases - powah anyone can taste and smell..

I have always assumed the CVK would respond/function exactly the same from one run to the next, given my carefulness to duplicate all variables from one run to the next. So far, I don't have any reason to doubt this assumption.

What I need right now is more information on theory. For instance: Most all 4 stroke curves, that I see online, taper off as RPM rise. I only found one that didn't - and it was a custom curve done on a dyno with a load cell (which is the only way to properly create a max performance ign. curve.) It flattened in the middle and then rose at the higher RPM's.. This continual rise at higher RPM's makes sense to me but it's quite outside the norm. I can find no information on why 99% of the curves reduce advance as RPM's rise...

Higher octane = slower flame fronts, vs Lower octane..

 

unlike diesels which are "fixed" compression motors ( fixed wide open throttle speed varied by fuel control), Gas motors are variable compression, speed varied by varied by inlet air control.
At full throttle and rpm the 250cc (is lucky) if it being filled with 250cc. This means is getting full compression, more compression requires less advance in the timing.

At lower rpms and throttle position, midrange for example, the fill is less, compression is lower, so more advance in the timing can be used.

The eaiest way to build a curv if you had access to a dyno is the fix the ignition at say 15 deg, dyno it across the throttle range, set it to 20deg dyno it, 25 etc etc. The interpolate the data on the torque peak per rpm. Figure out where the timing should be where. I paid to have this done with a small block Ford I raced back in the day. A delco remy distributer machine was then used to cam and spring it to a proper curve. Max timing was 24deg, this was on a motor that ran like 32deg stock fwiw. A reflection of the motors higher compression ratio and it's better ability to fill at higher rpms.