25:1 AFR limit?

[piledriver]

I'm seriously looking at doing a GDi motor with MS3 controlling it, with the 05/06 Mazdaspeed 3/6 injector driver box its a no brainer electrically.
...the 25:1 afr hard limit in the calculations may however cramp my style.
(I have run 22:1 in the past, but my current WB limits prevent setting that AFR, even though it used to calculate fueling ~perfectly)

I have a WBO2 handy what will in fact read to free air, but 40:1++ AFRs, fueling will have to be calculated.
I suspect the chamber setup will allow stratified operation (dual plugs and injector in exhaust pocket on 2V head with bathtub chambers)

If that engine setup doesn't work I'll aquire a TFSI head etc to bolt onto my Mk1 1.8 and start with a man on base.

I haven't done any coding in years, i sucked at it, much better with metal.
Would it be a difficult change or simply a limit in a variable?
I can drive a compiler.

[jsmcortina]

...the 25:1 afr hard limit in the calculations may however cramp my style.

AFR is an 8bit value in the tables. 255 raw value = 25.5 AFR. So that's non-trivial to change.

James

[racingmini_mtl]

One way to keep the 8-bit value would be to say that the AFR range starts at a non-zero value. So if you say that the lowest possible AFR is 10 you could go up to 35.5. You would then need to modify the computations but the tables would remain the same. You would also need to change the ini to reflect this.

Jean

[piledriver]

Processed this a bit and the "easy button" would probably be to simply lie.

... rather than rewrite perfectly working fuel calculations...
...cut the reqfuel number in ~half when in modes that need higher than 25:1 AFR.
Its not like it can be measured with a typical WBO2 unit anyway.
(can it be measured down stream at all?)

This has sort of been discussed previously, (richer for E85 etc) not sure if it is a planned feature yet.

I have a long row to hoe before I'll get to even try it on an engine, but it works on the bench, utterly transparent to the MS2. The only issue I see is the injectors are relatively huge, ~never used over ~50% duty cycle, and the dead time (due to the 100V pulse at leading edge drive signal) is probably ~500us or less. I suppose as long as I don't attempt stratified charge operations, its NBD.
(although that is ultimately a goal)

The HPFP seems to be the main showstopper, most newer versions use a synchronized PW to a solenoid making the pump variable displacement.(holds the inlet valve open various % during pump stroke to vary pressure)
I cannot see how to drive that with existing hardware/FW.

At least the std Ford/Mazda fuel rail pressure sensor is 0-5v.

I suspect some 1st gen HPFP designs use a std PWM regulator.
Perhaps Mitsubishi and the European Ecotecs, easy to drive unit pumps too, but seem hard/expensive to find used, esp in USA, I'm not sure I can really see everything on the European Ebay sites, or the general selection really sucks for used car parts.

One other possible pump is the 3 piston Standyne pump used on Mercedes M272s (3.5l /6) Standyne indicated their pumps are or can be made fully e85 capable. No other GDi pump manufacture even allows E15.
OTOH I have yet even been able to find a part number for one of those...