LS2 Idle Tuning - Who is up for the challenge?

[Cyclone Chris]

Well, gotta say... this LS2 Idle stuff is a whole lot different than LS1's. It's acting all kinds of crazy on me.

This is whats going on.

1. I'm currently tuning in SD and do not have plans right now to use a MAF. All other fuel adjustment aids turned off. Car is currently in OL
2. After every Calibration Write, Motor starts right up with a hesitation at 500 rpm, then up to commanded idle.
3. AFR starts at 16.7 (Idle) cold, then works itself down to 14.5 AFR (Hot)
4. During Warmup, the car is spitting a bunch of black stuff out of the tailpipes (maybe unburned gas) along with some strong fumes. (This problem sometimes goes away after a few days driving) Is idle learning something here??????
5. While driving around... all is great for about 10 mins, then when I get to a stop light the car will initially go to 950 idle, then jumps to 1200 idle and remains there for the duration of the drive. AFR is at 14.7 @ this point. Seems like something is overriding commanded idle????
6. Also at cold startup I occasionally get a slight surge during the first 10-15 secs. I can actually hear the motor changing it's whistling pitch here. (Maybe Startup AirFlow Table????)

I know this isn't much help without a log or tune attached, so please let me know what you guys want.

Startup Idle (Cold) - what parameters logged????
Startup Idle (Hot) - what parameters logged????
Tune
Any Idle Histograms out there for LS2's????

Thanks
Chris

[PBMFIsMe]

Good Luck......When you figure it all out, you can show me how its done at FL Vs GA next month....LOL

[Cyclone Chris]

Damn??? Is this LS2 stuff that hard?

[Cyclone Chris]

Well, I went out logging today and when I got done, I filled up my gas tank, and started up my car. It jumped up to 500 rpm and stalled on me. I started her back up and she had a hard time starting back up.

When I got back home I logged a few Hot Startups and as you can see from the log, everytime I start her up she'll hesitate, climb up, then idle correctly. I've tried raising the Startup airflow table up by 1gal/sec and it seemed to get worse.

Any ideas?

[PBMFIsMe]

Apparently there are some radically different Idle tables for the LS2 over the LS1.

I read one post where Chris@HPTuners said you'd need to be a mechanical engineer to tune the idle on one of these things.

I settled for just lowering my timing a bunch at idle (10*) to keep the RPM down around 1000. High timing (25+) like what is suggested for LS1's makes my idle go up to over 1200 RPM and makes an annoyingly loud bit of valvetrain tapping.

One of these days I'll make a real run at trying to tune in the Idle airflow. If I get it figured out, I'll send you my tune so you have something to start from.

Mine kind of does the same sort of thing with the Hot Startups, but it doesn't usually stall. I figure if I ever get the normal Idle stuff working, I will have some more knowledge to pull from for working on the hot starts.

[EC_Tune]

Your base running airflow needs to be 10.5 at the 800 RPM line and 11.5 at the 1200 RPM line according to your dynamic airflow values.

Also increase the startup airflow by about 5-6 g/sec over your stock table. That should help. Go up in increments of 3 to get a good start & run.

[Cyclone Chris]

Your base running airflow needs to be 10.5 at the 800 RPM line and 11.5 at the 1200 RPM line according to your dynamic airflow values.

Also increase the startup airflow by about 5-6 g/sec over your stock table. That should help. Go up in increments of 3 to get a good start & run.

Thanks EC Tune, I'll give that a try when I get home this afternoon and log startups. I'm assuming Base Running airflow changes are only necessary for Neutral/Park right? Should I change startup airflow for all temps?

I'm trying to tune 3 parts to this car. Part Throttle is complete, now all I have left is 4K RPM+ and Idle.

Thanks Again
Chris

[Cyclone Chris]

EC Tune,

I did what you recommended, but it seems like it got slightly worse or just the same.

Attached is the tune with the startup airflow and base running airflow changes along with cold/hot start logs.