Thunderace EFI - Day 10 using MSExtra 3.0.3u

Well I got MegaTunix going early next morning, and all I did was upgrade to the "git" version, and it worked thereafter.

Anyway, I’d thought I'd test it out on the bike, so another trip was needed to look at the compensation issues. The conclusion is this whole battery voltage injector compensation thing is quite testing, which is compounded by the poor state of the battery, but this is a good learning process and can only mean better refinement.

I found I am using really small values for the adjustment now 0.050 msec/V from the default of 0.200msec/V, but obviously I am playing around with the Req'd Fuel & Injector Opening Time. It looks like I might have to change the VETable resolution, because at stoich the difference between 16 or 17 in the VE bin sends it too rich, so I'll be doubling the numbers and halving the fuel.


I did manage the above, but I think the compensation was 0.00msec/volt, but under cranking it was a big starting issue, as the 9.0V under the starter, affected the idle and ASE quite a bit. I rounded off my hour or so of tweaking by adjusting the acceleration enrichment tapers, after switching AE on of course.

However being an Alpha-N/ SD blend, I spent quite a bit of time reducing my very small part throttle openings, as they were far too rich, which means modding VETable 2. This actually works rather well without having an acceleration enrichment enabled, and I can see this is a useful tool to smooth out very small throttle transitions. It would be a lot more useful to do this under some load, but this bike isn't on the road yet, and the rear end is being overhauled I can't dyno it, as the wheel and other stuff is pulled out.

I also played with the TPS/MAP blending and the thresholds, and got good "very sudden snap open throttle" response by lowering the MAP threshold from 150 to 120. I also have very little ramp slope/gradient on my AE curves, as I am running way too rich under acceleration, and this is a lot different to how I started.

I am using 3.0.3u at the moment, and surprisingly I did notice the ASE light coming on when blipping the throttle, and revving the bike, which I'll be looking out for again next time I play with the engine, as it could be a bug.

Finally, I got MegaTunix 0.9.22 hooked up to the engine as a parallel development in OSX on the MacBook Pro, and other than a need to rework the gauge limits/layout, it is surprisingly fast and quite a bit different to TunerStudio. Obviously I am used to the latter, but MegaTunix looks like another useful tool in the MicroSquirt tuning library.

Next up is rework the .ini file so that the AFR readings can be used to tweak the VETable automatically. I probably need to restrict it to one table, VETable2 as MAP fluctuates quite a lot with very small throttle openings.

Tables look like this now...and the refinements are just right of idle around 65-75 kPa (fuelload% in this graph below), in VETable2.


Thunderace EFI - Day 9 using MSExtra 3.0.3u

Another chance to do a bit on the engine today, and it's been a while, but I have been on holiday for a few weeks.

The bike was resistant to starting on the low battery. It wouldn't quite catch, so I checked the fuel...and that was that

More fuel in the tank and after a short time I switched on the LC1 and immediately noticed the engine was running weak, so I decided to tweak the WUE values closer to stoich, and continued to do so as the engine warmed. The idle was relatively steady, the VETable 2 SD blue dot holding in a tight group, and then the fan cut in...suddenly the engine went richer. I had noticed this before, and homed in on the voltage compensation for the injectors, so I tried to bring this closer to stoich, by reducing the compensation...however when the fan stopped the previous stoich setting was too weak.

I jumped a battery across the system to try and stabilise the fluctuations, but it made hardly any difference. I tried reducing the injector time, required fuel, VETable bins etc and modding the correction, but it was never 100%. I need to mod the dash next to view in realtime battery voltage, PW and AFR, as I think this is the main reason for my idle fluctuations, and taking a snapshot will prove this. I know I can use MLV, but this is good enough.


The screenshot above from the left after the fan cuts in, and the engine is too rich, when it stops it's close to stoich, AFR=14.7:1

Interestingly there is no lag compensation for "battery voltage", yet there is for other sensors, and other stuff.

The other few things I tried was very small throttle openings and tweaks to the SD VETable 2, just off and around idle, and at the same time maintain close to stoich, which is not what you’re supposed to do, as you try to get the lowest MAP value & smallest fluctuations in RPM, but I can refine this later with a target AFR table. By the time I had enough, it was starting to get very much smoother, and I really enjoy working with the TunerStudio software.

Incidentally, I did try MegaTunix in a back to back attempt, but I couldn't get the USB Serial adaptor to be seen in X11, and so I must be doing something wrong.