How big does a cam have to be to have surging no matter what?

[99LS1SS]

I'm just trying to figure out if I'm fighting a losing battle or I need to work harder. It isn't surging bad but it surges a little in 4th when cruising at about 1500 RPMS. It hunts for idle when it's cold too. It idles fine when it's warm though.

This is a LS1 408 motor.

*Edit - The idle hangs at 1500 when I pat the gas. It eventually settles down but it takes about 5-10 seconds.

The cam specs are:

242/250 .612"/.612" 114 LSA

Thanks.

[DSteck]

With 18º of overlap, you'll be hard pressed to COMPLETELY eliminate bucking in gear.

There's no reason your idle should hunt when it's cold, or hang after you rev up. Sounds like you just need to work on your idle tuning more. Get your minimum idle airflow dialed in, and make sure you aren't running more spark than it actually needs.

[jimmyblue]

It's my belief that any of them can be settled down,
but you may have to work on things you didn't plan
on.

For example I have seen what look like fuel-loop
oscillations, which I believe are from a mis-calibrated
VE table in the MAP dimension (more MAP makes a
rich fuel error, raising MAP more, over/undershoot
continually). Same for too much spark-MAP (CylAir,
follows MAP). Having a closed loop fuel trim cell
boundary that sits right where you cruise, bad too
(dunno if you are trying to run closed loop with big
cam, the O2 sensors' response down low may be
"interesting").

Making a spark table that's flat vs g/cyl in the cruise
regions is a thing to try, similarly experimenting with
modest MAP-slope variations in the VE table. Looking
for clues from response.

[WS6FirebirdTA00]

A lot also has to do with how the rest of the system damps the surges out. Surge is one thing while in gear, but there is no reason to get surge just sitting at idle.

[99LS1SS]

Damn this is whipping my ass. What do I need to adjust to make this car start up and idle on it's own when it's cold?

[DSteck]

Make it idle higher when coolant temp is low, and add startup airflow. Also, adjust your timing in your idle map so it reflects what the engine actually needs to idle.

[99LS1SS]

Do any of these tables looks obviously wrong? And should I look anywhere else?

[99LS1SS]

It isn't even making it to 1000 rpms at cold startup. It struggles at ~700 rpms and then dies. I can keep my foot on the gas and keep it running but I don't think I should have to do that....should I?

Here is the most recent tune.

I added the current tune.

[WS6FirebirdTA00]

We need a cold start log with relevant info. Your IAC may be maxing out on cold start. Your RPMs look way too low and so does your timing. I cant open your file, but what is your over and under speed spark correction? That plays more a role than the IAC will (unless you changed the PID tables and made them too aggressive).

[DSteck]

His timing looks high to me. The Gen IV motors don't like a lot of timing at idle. My monster cam LS7 idles with 17º... any more, and the adaptive controls pull it out.

Cold idle rpm does look low, though.

[WS6FirebirdTA00]

I just assumed that with the user name that it was a 99 LS1, didn't see the sig. Moving this to gen 4.

[99LS1SS]

I just assumed that with the user name that it was a 99 LS1, didn't see the sig. Moving this to gen 4.

Actually, I am tuning a 99 SS. It's a 408 cid with a 242/250 .615"/.615" 114 LSA cam and Dart II ported and polished heads.

[WS6FirebirdTA00]

Ok, edit your post with that in it please. I will move this back.