@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?

 

I am glad i helped you do that
I ride 6000-9000 rpm
And how about fuel octane rating?

 

Klx250/300 compression ratio is pretty low - 11:1, so regular octane is fine, I use 92 without any issues.

 

Hi Folks. New set of charts from me. Unfortunately I lost my old tyre on which I made all my previous runs.
The First chart
So I purchased new D605 and made dyno run with my old setup to compare what will be dyno loss with new tyre. It's 10% (28hp new tyre vs 30.8hp old tyre). Red is new D605 tyre, blue is my old D605 with almost zero tread. Same mods - full exhaust, open airbox, JDM ECU, fuel controller.

The second chart
Demonstrates power curve for throttle body increased to 38mm and camshafts from klx300r (2020+) (RED) vs standard cams and throttle body (BLUE). As you can see cams add a bit at the top (29.1hp, which is ~ 1 hp top power difference), but loose a bit at the bottom. Which means with 300r cams on street tyre klx300 would show about 32hp from the wheel.
But after having a ride I barely feel the difference between two setups honestly. So I don't think it worth it to spend money on cams. I also measured 34mm throttle body vs 38mm body and old cams and 38mm throttle body doesn't offer anything over 34mm. Curves are essentially the same.


4000km worn D605 (blue) with brand new D605



Standard cams + standard throttle body (blue) vs 38mm throttle body + 300r cams

 

Did you check the curves for 34mm + cams ?
34mm would maintain "stock velocities" thru the induction system, allowing a direct comparison of the two cams' effects.

Did you refuel the top end to correct for the increased VE with the 38mm+cams ?


The power curves gets pretty "sketchy" on the top end. Such curve issues can be ( or ARE ) due to tire-roller contact problems. If so, the power curves would be significantly higher with proper tires and tire-roller contact.
It would seem the 10% loss you calculate (due to faulty tire-roller contact integrity) may be quite a lot more in the top end range.


In a nutshell: From what I see, I believe the power increases are higher than your current data shows.

 

I think you are right and top endught be better than chart shows. Ive been riding today quite a lot on the paved roads today and top end indeed feels stronger.
Unfortunately I didn't measure 34mm throttle and 300r cams. I first installed 38mm throttle, made dyno (which has shown slight improvement at overrev compared to 34mm). Then I installed cams. Of course I did refuel for each setup. Fuel adjustments were minor though.

My main hope with 38mm throttle body was that kdx snorkel+ 38mm throttle would work similar to lidless setup. But no. Kdx snorkel is still minus 2.5 across the whole range.
See one more chart below.
Red - old cams, 34mm throttle
Blue - old cams 38mm throttle
Green - new cams 38mm throttle
Pink - new cams, 38mm throttle, kdx snorkel