@tsc , let me try to convey something:
A given AFR value creates a given flame propagation rate. Leaner AFR starts to burn slower (after a certain point) , Richer AFR burns faster (to a point). Knowing these "points" is what separates ICE engineers from your average "tuner"..

Now for the info no one knows - but is slap-your-mama-stupid obvious : Different AFR's have to be ignited at different points in time in order to produce max cylinder pressure at (approx) 15° ATDC.

The ignition scheme and the fueling scheme are joined at the hip - ignore this and you are part of the 99th percentile, use this, and use it successfully, and you are part of the 1 percentile.

You can NOT take a given ignition scheme, change AFR to various rates, and expect any significant results.
Instead, such a practise could have negative consequences - A stock ignition system optimized for 12.1 @WOT could detonate if fed an AFR of 12.6 due to the increased burn rate of 12.6 compared to 12.1. An ignition system that is optimized for 12.6 would be too retarded for an AFR of 13.2...

Best Practises:
You cannot know anything until you fully understand the stock WOT fueling. Barring an intentional software detune from the OEM, the ignition system will be optimized for the stock AFR@WOT. This is where you begin PERIOD. Lots of times, all that needs to be done is to slowly raise AFR from a overly rich stock target, to a faster burning target ( 12.5 - 12.8 inclusive ) .. However, if a few additional degrees of advance can be tolerated as well, the results are magnified.

 

Watching this with great interest!
It will be a winter project for sure.
I was planning to do the BB 351 it if the ECM part was taken care of.
I have done some tuning on GM efi cars from simple Cavalier with was to much cam and oversized injectors to Gen 4.
I believe there will be a way to adjust the whole engine management and when I can reliably, I will do that.
I will do it with the safest , most reliable setup as well as the quietest exhaust and intake that I can get away with.
Reliability first, USABLE power second.
Keep up the good work here.
Thank you for sharing.

 

Thanks! I think I'm almost done with engine mods. The last bit - klx300r/ninja z250sl camshafts. I have spare pair which I got almost for free. Will install and run dyno next week.

 

I visited by mechanic today who had ordered me a replacement ApiTech standalon under warranty. We will fit it and run it till it dies again. He told me he knows a company here in Vietnam and the have a standalone ECU in development specifically for the KLX and I plan to fit it and test once available. The klx is one of two street legal dirtbikes here and everyone is tired of ecu woes. Hoping they get it right!

 

I have a spare throttle body. Gave it to machine shop to bore it to 38mm and make a buttefly. Maybe it's a stupid idea, and 38mm will loose bottom end compared to standard 34mm, but I feel there is potential there. Having seen 2hp from just removing airbox lid I suspect increasing intake airflow should be beneficial. Time will tell - will report here once I will fit and test it.
Your thoughts, gents?