E40 ecu confusing idle results after cam install

[dankmac]

Hi guys.

Hoping someone can take a peek at my tune and logs and see if this behavior is as expected. I had the idle control for airflow and spark turned off for initial startup, and just threw some very desensitized numbers in there to go for a drive around the block. This is very preliminary stabs at getting the car driving around with the bigger cam.

The car is a MAF controlled stroked LS2, 402 cubic inches, stock LS2 throttle body, stock ls3 intake and heads. Previous camshaft 226/242 on 117, just installed a 242/250 on 114. 0* overlap vs 18* overlap at .050" lift.

I expected needing a lot more base running airflow and timing at idle so to start with I bumped it up in both areas. It wanted to idle at 1400 rpm.

I have been dropping and dropping both idle airflow and timing and still struggling to get the idle down.

Previous idle was stable and well controlled at 850 rpm with ~18 degrees idle spark and a good TB calibration.

I have now reduced idle airflow by ~30% in the idle regions vs old cam tune, and it is still idling at average about 5 degrees spark advance to get the rpm down.

This is completely counter intuitive and I'm really not sure if I should keep going down this path of reducing base airflow, or if I should start considering that something is wrong with the tune or the engine (vacuum leak, unmetered air?).

I took it for the first drive and the log is attached. It drove around well enough, choppy as expected, but really didn't have much of a problem idling and driving around. It did stumble a few times, mostly I think due to off idle timing issues of not having enough advance, and I do have a 30 lb RPS clutch/flywheel combo.

It also didn't make shit for airflow on the one third gear pull I made which is something that I hope improves over time - although it is a massive heat wave here in socal right now and I'm sure the air is trash.

Thanks for any advice you guys can offer!

1. SWAG idle settings - current tune
2. New cam first drive - big cam log
3. Baseline old cam tune
4. Santiago drive - datalog with old cam

baseline old cam tune 8-16-20.hpt
santiago run.hpl
cam first drive.hpl
SWAG idle settings.hpt

[dankmac]

It was recommended that I might have too much fuel going through it at idle. I?ll try forcing open loop and see how it behaves. Will update with results.

[momotunes]

I don't have my computer with me to look. If fueling is correct than disable adaptive idle by zeroing out proportional and integral for idle Airflow. Leave spark on for adaptive idle. Max out Airflow final minimum. Lower your ETC percent max to something low like .41. start engine. If idle shoots up out of control than shut off and lower etc percent max. If it won't start than add. Flash and try again. If idle comes back down pay attention to spark advance. If it's lower than what you have idle timing set for (problem you have now) than lower etc percent max. If timing is higher than commanded than add to etc percent max. Keep going until your idle is stable and timing isn't moving around to control idle. Once your happy start a log and watch airflow compared to rpm (like Airflow minimum table). Get the average Airflow, take that, and subtract 5 percent from it. Put that number in your Airflow minimum table. Do that and put etc percent max back up.

ETC percent max = maximum throttle opening at idle

Airflow final minimum = minimum Airflow motor can take to sustain that rpm.

Throttle moves between the two for idle. If rpm is too high spark is lowered. ETC will try to adapt and timing will try to go back up. If throttle can't close enough than timing is held back. When timing takes huge swings so does manifold vacuum. Increase vacuum will increase rate of pcv airflow. (Yes I know MAF is supposed to take account for PCV airflow however does it really know how much that air it accounted for is going into the manifold at what rate? When manifold vacuum swings around you imagine what's going on in there further adding to the tail chasing.).

If fueling isn't correct you will have to start higher and work your way down.

I had one car that no matter what I did it wouldn't respond as soon as I put etc percent max back to stock. I can't remember exactly what I did (don't have my computer with me) but I know it had to do with torque table. I look at it tomorrow.

[dankmac]

Thanks for the reply. For some reason I can't pinpoint because I was moving a lot of things around the idle is now behaving like expected. I can dial it in from here now that the changes are properly reflected by the car's behavior.

[smokeshow]

There's a ton of stuff missing in the definition from HPT on this one... Just about impossible to do it right. No use in going into any detail, but a couple tips to make it a little better... Set the minimum setpoint for rolling (VSS) idle equal to 950, your lower target idle RPM. This will prevent it trying to yank out spark on coastdowns to meet an idle RPM it can't get to. And I would at minimum put the idle integral airflows back to stock. Adjust proportional after that if necessary.