Basics for tuning with a larger cam

[LuhrsTSF342]

I think I have the higher RPM stuff figured out but the idle stuff has me,
Can someone give me the basics for idle on a 230-236 114 cam in an LS2 ?
I've been told I should have more timing that stock and be richer.
How can I get it to idle at 13:1 (I'm assuming that's what I need to do) if the PCM wants to bring it to stoic?
Any hints to get me started?
Thanks, Robert

[Tordne]

Tell us what about your idle is no good and that will give us a starting point to make suggestions :).

If you are running Closed Loop the PCM will trim to achieve an AFR of 14.63:1, so if you want/need to idle richer Open Loop will be your friend.

Common things that people with cams have to change and the Throttle Follower decay rates as often the car dies if the throttle is blipped.

[ringram]

Desired Air Flow using RAF pids is pretty essential.

Use the bidirectional controls which forces open loop I think, to command different spark and fuel until you get a nice idle. Remember smoothest lean idle is best. In my case fueling is stoich, but spark is around 28*

Maybe crank idle speed up a little until you get it smooth, then you can probably drop it down again once you have airflow, spark and fuel right. My 282/286 with 56* overlap idles at 740 no problem.

For hairy cams you can even look at COS5 and exclude unstable map readings from your fueling calcs.

[redhardsupra]

LS2's dont have a RAF table, that's the whole problem, ringram :( so i guess what we got left for LS2 is just upping the RPM till it gets more normal, and even more attention should be paid to VE than usual. idle spark also helps, as the LS2 computers dictate some ridiculously low amount of timing stock. soon i should have LS2 with a 24x cam in it to play with, i'll write something up for it.

[ringram]

Ok, just efi doesnt officially support ls2 yet, so it might be ls2 in an ls1 application, but good point (and news to me) Maybe tsf342 can clarify.

I see there is a minimum idle airflow table in the ls2 though. Maybe that can help?

May be a good time to remind the board admin's to set up an LS2, E40 tuning section :)

[Redline Motorsports]

Ok, just efi doesnt officially support ls2 yet, so it might be ls2 in an ls1 application, but good point (and news to me) Maybe tsf342 can clarify.

I see there is a minimum idle airflow table in the ls2 though. Maybe that can help?

May be a good time to remind the board admin's to set up an LS2, E40 tuning section :)

Exactly! :)

[LuhrsTSF342]

It's the occasional surging and falling through the 750 that I'd like to maintain.
It idles reasonably good and then all of a sudden it just falls through the 750 threshold and then surges to try and stabilize itself.
I'm sort of new to this so I'd have to really look and see what I've done so far.
I don't remember off the top of my head.
Can you put it in open loop for idle and closed loop for cruise etc? If so, how?
BTW: Just to clarify. It's an LS2 based 402 in a C5. LS2 throttle body etc.
Thanks for the input so far.

[bink]

It's the occasional surging and falling through the 750 that I'd like to maintain.
It idles reasonably good and then all of a sudden it just falls through the 750 threshold and then surges to try and stabilize itself.
I'm sort of new to this so I'd have to really look and see what I've done so far.
I don't remember off the top of my head.
Can you put it in open loop for idle and closed loop for cruise etc? If so, how?
BTW: Just to clarify. It's an LS2 based 402 in a C5. LS2 throttle body etc.
Thanks for the input so far.

Use BiDi to maximize Idle timing. Bump up the value a little (few degrees and then let it (engine) settle at new timing. Do this till it surges then back down to nonsurge timing- you may get as high as 40*. Also...then increase throttle follower airflow.

FWIW.
:cheers:
joel

[Bruce Melton]

I am running 35 deg with a LS2-402 C5 which helps. In order to get good transtions coming off idle I had to do AutoVE which did an amazing job in taming cam bucking etc. and idle..
Still trying to get the MAF back online but that is another story.