Engine stalls when ASE ends – needs ~200% AfterStart to run (Alpha-N, EMU Black)

GENERAL
1

I’m looking for advice from experienced EMU Black / Alpha-N users.

Engine runs normally only while AfterStart Enrichment is active.
To keep the engine running during warm-up, ASE had to be increased to ~200%.

With ASE ≈ 200%:

  • Engine runs and idles normally

As soon as ASE ends (drops to 0), the engine stalls immediately.

Log observations:

  • ASE drops instantly (~200 → 0)

  • Injector pulse width drops from ~2.9 ms to ~1.5 ms

  • RPM falls rapidly and engine stalls below ~800 RPM

  • Sync loss happens after the stall (not a trigger issue)

Additional info:

  • Alpha-N fueling

  • Lambda sensor installed and working

  • Increasing Alpha-N values and setting lambda target to 0.85 did not prevent the stall

  • Without ASE, engine cannot sustain idle at all

  • Closed-loop lambda may not be active (or not active fast enough) at idle

What I need help with:

  1. Is this behavior typical of too low base idle fueling in Alpha-N?

  2. Recommended minimum injector PW at idle for stable combustion

  3. Best ASE decay / ramp strategy to avoid fuel cliffs

  4. Should lambda closed-loop be active during or immediately after ASE?

  5. Any EMU Black specific settings that commonly cause this issue

Any guidance or real-world experience would be greatly appreciated as my trying months to see what happened.

ZX12R_13_factory_data_new4.emub3 (64.5 KB)

20251214_1456.emublog3 (183.2 KB)

2

Hi, I’ve not pulled up your log (or ECU file) but the behaviour you describe would normally be indicative of the VE table being grossly out, how certain are you of your injector size, fuel pressure settings etc?

Secondly, you have tuned the VE table?? Because start/ idle etc. is meant to done on a (more or less) completed VE.

I support a race car that uses GSXR ITB’s on a 1588cc 16v engine with silly cam, part of ‘getting it to run nice’ was making sure they were properly balanced, also, I don’t know about yours but the GSXR units had a bunch of air bleeds that needed blocking off too.

I run closed loop lambda (IIRC 0.98 at idle) but not till 50degree CLT temp, when I change it over to V3 I will start the closed loop lambda sooner as V3 allows lambda vs clt temp. During warm-up (from clt 15 ish degrees) I run 0.9 ish.

Simon

EDIT, pulled up your ECU file:

  1. Your on beta 56 version of the V3 software, not a massive issue in your case but best to stay up to date and there is a consumer version available!

  2. Your VE table is NOT TUNED, and frankly wouldn’t run a lawnmower. Either sort your VE table or pay a professional to do so

  3. Your ign table is super aggressive, that may be ok for ZX12 but I’d STRONGLY advise you start with lower values and tune up to MBT (or knock)

1 Like
3

Hi Simon, thanks a lot for taking the time to look at my file and for the feedback.

A few clarifications from my side so we can focus on the real issue:

  1. Software: I have now updated to the latest consumer V3 (I was on beta before, agreed).

  2. Fuel model: This is an Alpha-N setup (TPS vs RPM).
    Also, what you are calling “VE table” in my file may be a misunderstanding: the table values you saw (around 14.1 / 13.8 / 13.6 / 13.1 / 12.8) are AFR / Lambda target style numbers, not VE%.
    So it’s not an untuned VE table in the traditional sense — it’s a target/AFR-style table (happy to be corrected if EMU shows it differently in this mode).

  3. Ignition: My ignition map is a 1:1 copy from the OEM ZX-12R ECU as a safe baseline (not a “random” map).

  4. Injectors / pressure / dead time:

    • Injector size currently set to 320 cc/min

    • Base fuel pressure 3.0 bar

    • Dead time table is copied from the OEM-derived data I have (I can share the exact table if needed)

  5. Actual problem (from logs):
    The engine runs normally only with ASE around ~200%. The moment ASE ends (drops to 0), injector PW drops roughly from ~2.9 ms to ~1.5 ms, RPM collapses and it stalls.
    Sync loss happens after the stall (not the root cause).

What I’m trying to understand (and would really appreciate your input on):

  • In Alpha-N, what is a realistic minimum stable injector PW at idle for these bikes?

  • Best practice for ASE decay / ramp to avoid a fuel “cliff” when ASE ends

  • Whether you recommend enabling closed loop lambda at idle earlier (with limited authority) to smooth the transition, and how you usually stage it vs CLT

If you point me to the exact page/setting in the file that makes you conclude “VE not tuned”, I’ll gladly re-check, because I think we may be looking at AFR/target style tables rather than VE%.

Thanks again,

Stef

4

I think you missunderstood ve table with lambda target table. You need to tune it warm then play with Cold starts

5

Stef,

I’m sorry but this is not how this works, I get paid to install standalone ECU’s and tune them. I come on the forum to help out when I have 5 mins, not to do remote setup free of charge.

Without wising to be rude, you do not seem to be competent to setup/ tune your chosen project, I would STRONGLY recommend approaching a (local) tuning professional.

As kimbaku (correctly) stated above, you have misunderstood VE table vs Lambda target table.

What you think is Lambda is not - it’s VE

With ignition timing (even with a direct copy map), it’s good practice to pull things back a bit before starting the tuning process.

Good luck

Simon

6

Hi Simon,

Thank you again for taking the time to reply, even briefly.

I fully understand and agree that for many people this is professional, paid work.
My intention was never to ask anyone to do the project for me for free, but also not to lose the enjoyment of learning and building something like this myself.

Both you and Kimbaku helped me complete the missing pieces of the puzzle and correct my misunderstanding, and I’m genuinely grateful for that.

Regarding ignition timing, I will pull it back a bit as you suggested and continue from there.

Thanks again for your input.