DFCO issue with Dynamic Airflow enabled : Lambda stuck at 0.55 sometimes

[Sachs]

Guys,

I'm fighting an issue with DFCO when Dynamic airflow is enabled... Working on finalizing driveability of the car...When I tuned on the dyno engine made 555WHP/490WTQ on E75 (Katech Stage 2 engine)

When I do a quick throttle tap or WOT then off at low medium rpm, the engine sometimes does not go to DFCO. Injectors keep dumping a ton of fuel, lambda goes to 0.55...
Airmass show crazy values (0.54g with 0% throttle)...Commanded Lambda is at 1.00

In MAF only I don't have the issue. Also when I disable DFCO and have Dynamic Airflow enabled it almost never happens.

I think there is possibly an issue with my VE table (tuned to 3-5%) but I don't understand what exactly... I saw that when I happens I have a pretty big discrepancy between MAF airFlow (10g/s) and VE airflow (14.5g/s)... But even at 14.5g/s my injectors should not dump so much fuel (2.8ms !!! )

Looking at my log and tune do you guys see an explanation ?

Also I have the butt feeling the car has more torque down low when dynamic airflow is enabled compared to MAF only ???

KATECH ISSUE.jpg

[Sachs]

Anyone ?? I spent again some time yesterday trying to figure it out with no luck....

[Craig18SSA8]

Looking at your VE table, you made the same mistake i did and pulled too much fuel out of the low load zones, as well as low rpm zones.

What i did to fix this is i returned all of the low load and low rpm below idle back to stock on VE.

[Sachs]

Looking at your VE table, you made the same mistake i did and pulled too much fuel out of the low load zones, as well as low rpm zones.

What i did to fix this is i returned all of the low load and low rpm below idle back to stock on VE.

Thanks I'll try that. How can that impact DFCO though ?

Edit : my VE was made with my wideband. I compared the values with stock and at low load and low rpm on my new table is very close to OEM

Having hard time believing it is coming from there.

[Sachs]

I just put back my prediction coefficients in dynamic airflow to OEM (everything was 0'd)

When the weather will permit, I'll do a test

[TriPinTaZ]

-Go to the ECU and navigate to Fuel > Oxygen Sensors > LTFT Idle Cells Thresholds
-Change the "Enable VSS" to 255 MPH
-Change the "Disable VSS" to 256 MPH


To be honest, I don't exactly know why this fixes DFCO issues. But I've fixed two cars like this already. I suppose it allows the car to go into idle mode regardless of speed which then forces DFCO based on the other parameters defined in that area of the tune.

[Sachs]

Thanks for the tip, I'll give it a try

I'll report if it fixes it. Though like you, after looking at it I do not see how it could fix DFCO ?? But at this point everything is worth trying...

I spent 2H yesterday looking at my tune and log and could not find why the car was not going to DFCO. In fact, it stays in CL (closed loop) when it happens instead of OL (accel/decel). This is really weird. I need to mention again it does not happen in MAF only mode, only happens when Dynamic Airflow is enabled. But my VE is pretty close everywhere so I do not understand how it could cause that....

[Sachs]

Looks like it solved it, at least on 91 . I need to try on E85 as I do not remember if I had the issue on 91...