E85/alcohol ignition timing

[RomChip200]

I'm chasing down the best timing for E85 in corner cases for VG30DETT.

My thoughts:
_when cruising, 38° 2500-3500rpm is optimal. Going higher than 40-41° for high rpm/low TP brings nothing
_cruising with AFRs=18 is not a problem on E85. YOu may feel a small jerk when transitioning from 14.7 to 17-18 but once it's steady, the car enjoys AFRs=17-18 and fuel economy too
_very low TP (TP=8-10), throttle slightly opened requires enrichment (TP_MIN), especially on bigger injectors. Otherwise AFRs reaches 19-20 and car starts to be jerky. We are very close to idle pulsewidth here but the car is still on load, so need to compensate
_sure, the timing map is really flatten out, till 30° for high TP (TP ~70 ~5psi), not a problem. When boost increases, I decrease in the 24-28° range for safety
_deceleration timing according to RPM seems to be too low. OEM is 15/20° but gives a jerk when transitioning from very low throttle (38°) to idle/injection cut (TP<8). I'm going to try 30°
_below 2400rpm, low TP, some audible knock occurs. Timing is 32-34° range till 25-20 as TP increases but going below makes the car sluggish even if knock seems to be less audible.
_warmup/cold timing needs to be in the 40-45° in the 2000rpm range. Anything below (especially the OEM warmup timing of 20° ! to be disabled) makes the car jerking. Anything higher (as it is the case with unleaded) will produce audible knock when cold.
_idle cold timing. OEM is 35° (15 warm+20 cold). 40° works fine, maybe rpm is higher when cold (2000rpm @0°C)
_OEM has very low timing for very low rpm/ high TP (right bottom of the map). This area is exercised when you start from full stop or going backwards. 400-800rpm shows 2-8°. I put 16° for E85 with no side effect. Exercising this area when cold still makes the car jerking: I'm still looking for the best timing in this area when cold: 15° or 30° ? Not sure if timing can change something there, E85 combustion on very cold engine is complicated. I see 4-5ms injector pulsewidth there (limited by TP_MAX table), enrichening or leaning out this area does not seem to help. No problem when engine is warmed up.

Interesting thread:
https://raceone85.proboards.com/thread/ ... ion-timing

ignition_timing.png

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