Need help with fueling/airflow

[neond123]

Well, here I am at the mercy of the forum again. I've gotten my swap running fairly well, (off-idle hesitation, startability, etc.).

I have been able to put about 55 miles on the car. However. I still have some lingering issues.

Right now, my main problem is fueling issues, or possibly airflow issues. Basically, and only recently, DFCO seems like it's not even working. If I'm accelerating and then let off the throttle, the car will hang at about 1,000-1,200 rpms for a few seconds, and then drop down to idle (850rpm) while I coast to a stop. The problem is, when I slow down to about 5 mph or below, and drop down to idle at 850-900, the widebands peg full rich at about 10.5-11.5 AFR, 12.5 if I'm lucky. The problem gets worse and worse as the engine warms up. At op temp it sometimes even stalls because of the excess fuel. Not to mention it idles poorly, and I am nervous about possible cylinder bore-washing, hydrolocking, etc. Not to mention ruining spark plugs, widebands, carbon buildup as well.
If you make it back to idle without dying, and let it sit there, it will go back up to a more acceptable 13.8 to 14.4 range and then right around stoich. Fine.
Even when coasting, the idle drops down to about 12.5-13.0 AFR, before tanking to full pegged rich at 10-11 all of the sudden below 5 mph and at idle.

I've been tuning VE and MAF curve and I'm pretty pleased with cruising ranges and overall behavior/acceleration. But no matter what I do to the VE, MAF, or DFCO. I can't seem to keep the AFR from tanking right as I come to a stop. I tried re-enabling STFT in OL (I was running open loop-no trims), which seemed to catch it enough to keep it from stalling, but isn't quick enough to catch it before it's down to about 12.5. And the STFT is a remedy, not a solution.

Finally, as I suspect this may be related. When I am pulling the car into the shop up a hill, and I gas it, then let off so as not to kill the guy guiding me in, it stalls (when hot). Making it so I basically have to be on the gas until on flat land, and then slam on the brakes to not hit the aforementioned co-worker.

I suspect this has to do with rapid airflow changes, particularly sudden throttle closing, sudden MAP jumps, etc. Basically, from sudden low MAP to high MAP decel jumps, i run rich and stall. From sudden high MAP to low MAP punches i run lean.

It really only likes looongg, slowwww throttle changes. Dumps and spikes kill it and lean it out and richen it up and so on. It's super cammed and I haven't been tuning for long.

What transient, sudden-jump tables or adjustments should I be looking at?

Thanks in advance.

P.S Before anyone says it, my VE and MAF are smoothed.

[kingtal0n]

Why are you keeping the maf? Does the maf voltage spike when the engine is running rich? You can't use a maf unless you are absolutely a maf expert and understand placement and theory and monitoring the maf voltage for every transient. It's not impossible and it may have nothing to do with your issue but it sure as hell is an unnecessary additional component you probably would be better off without.

My advice is to watch where the VE table runs when you lift. In very high vacuum regions use very small map values, for example on the top row I have 0's in my VE table.

Next make sure the minimum fuel mg settings (all of them, including the minimum injector pulse table, short pulse adder, min fuel mg, transient fuel mg, or whatever its called, make them all very small if you have large injectors)
The computer can't go below a set amount of minimum fuel because of those tables.

DFCO can be tricky to set right. The tables labels don't even make sense to me sometimes. I suggest looking at the stock settings and trying to 'customize' them to your conditionals, which means logging the engine then comparing the result with the table.

finally people need to see the tune file to help and you won't get much response without posting it.

[neond123]

Why are you keeping the maf? Does the maf voltage spike when the engine is running rich? You can't use a maf unless you are absolutely a maf expert and understand placement and theory and monitoring the maf voltage for every transient. It's not impossible and it may have nothing to do with your issue but it sure as hell is an unnecessary additional component you probably would be better off without.

My advice is to watch where the VE table runs when you lift. In very high vacuum regions use very small map values, for example on the top row I have 0's in my VE table.

Next make sure the minimum fuel mg settings (all of them, including the minimum injector pulse table, short pulse adder, min fuel mg, transient fuel mg, or whatever its called, make them all very small if you have large injectors)
The computer can't go below a set amount of minimum fuel because of those tables.

DFCO can be tricky to set right. The tables labels don't even make sense to me sometimes. I suggest looking at the stock settings and trying to 'customize' them to your conditionals, which means logging the engine then comparing the result with the table.

finally people need to see the tune file to help and you won't get much response without posting it.

Thanks for the advice. I put it in speed density. Runs like a dream. I honestly think it's too cammed for the stock MAF. I think what happened was the MAF was spiking when returning to idle from the intake turbulence and overcompensating.

I put it in SD, OL, turned off decel cutoff. Runs fine. But my VE table was SO lean because of me trying to skew for the MAF it would barely accelerate. Much better now.

[gallegos276]

Post tunes and run logs and what done to engine