M20 fine tuning the fueling

[zaq123]

Ok so the car runs beautifully considering it has ITBs. Haltech Nexus S2 runs semi-sequential injection, stock cam driven ignition setup with stock coil ( for that authentic 80s look). Starts, drives, idles like a stock car.
The only issue I've been having - it was a little jumpy after the deceleration fuel cut aka overrun and the moment you go back on the throttle. My logs showed it was getting a little rich after the overrun


For those of you who use overrun or logged stock Motronic for educational reasons, what your AFR is doing right after the overrun? Do you see it goes from super lean/all air during the overrun (as it should) to momentary rich spike for a bit and then back on target? Do you see it's going from all lean to the target afr without a rich spike? I found out what my issue was and corrected it: basically I had post decel enrichment setup to wet runner walls as it all gets dried out during the overrun and at the same time I had too short of the delay for STFT (short term fuel trim) so it was dumping fuel too early, trying to correct normal lean conditions out of decel cut. I have STFT all figured out and pushing STFT post decel delay further into more meaningful AFR event when it's closer to target. So that took care of the issue of the overfueling.

My question is about fuel enrichment setting and what is better for the engine. Should I got from decel super lean event back to target AFR or should I let it go a little rich before AFR levels off?
It's an open loop event, STFT is out of the picture and not correcting anything yet in this event. Basically enrichment event right after the throttle is applied again and I can dial in how much I want that enrichment.
What's your thoughts, theoretically speaking...

[digger]

tune transient enrichment/enleanment on decel and accel by response/feel not by AFR

[zaq123]

haltech has STFT delay table that is only 2D (rpm scale is what I selected). So it's reserved for any transient events and I want to keep STFT responsive (picked only 0.1000ms delay across all rpm ranges). Post decel cut delay time is another animal where there is expected rush of free air aka super lean. I put a ticket with Haltech to see if they can make that table 3-d so I can dial a delay time for overrun separately from normal driving events. Haltech has a built in delay of only 0.100s of post decel cut limiter which is way too short. WB still reads super lean post decel +100ms of built in delay +100ms of my set delay in o2 delay table and STFT goes crazy to correct when it sees 25AFR (sees it too soon). I can make the delay larger in the table but it will be applied to all o2 events which would make STFT slow in normal driving events, something I don't want.
Luckily, Haltech has a generic timer function that I can set to start a count down from the decel event and set engine "overrun closed loop recovery" time that way. MoTec has that option which is much more direct way (actual prompt) than what I did round and about way in Haltech. But it's the same crap: the same delay across any rpm range which is not ideal. Exhaust gas will travel faster to WB at 4k rpm vs 2k rpm for example. You get an idea. But it's another issue.

Haltech also has fuel enrichment option when you come out from the overrun and that's what I'm wondering about. Open loop, at 15% enrichment the car feels fine but my log shows post overrun lean (expected), then it goes rich and then goes back up on target. At 10% post decel enrichment, car feels and runs as good, but it goes from overrun lean to very close on target and stays there.

So I was wondering if it's better to go a little rich after the overrun or dial it in so it goes on target and stays there?

I guess my tune is so dialed in at this point and I have nothing better to do but to go off the wall and nitpick.

[Panici]

Different engine/ecu combo on mine, but I just don't cut fuel on decel/overrun.
From what I've read, the fuel helps to cool hot cylinders (or was that exhaust valves?) after a WOT pull for a turbo application.

My car isn't a daily driver so I have no concern for fuel consumption.