big cam tuning tips, GMPP LS3/525

[arubenstein]

Hi,

I am working on a 2010 Camaro SS with an E38. Engine is not stock, it is a GMPP LS3/525 crate motor. My questions are really centering around idle.

I have a good feel for how to tune the idle well (been reading lots of tutorials and howtos), but one thing that is not touched on specifically is target idle timing. The stock tune is around 13* to 15* timing at idle.

The stock cam is 204/211 with 117 lsa.
The ls3/525 cam is 226/236 with 110 lsa.

What would a reasonable idle timing target be? i have looked around on the internet and many say that bigger cams should have more advance at idle, and that will lead to more torque at idle and smoother idle.

I plan on playing with some trial and error, but wonder if anyone has any pointers.

[swingtan]

I've played with timing setting a fair bit and found that the "functional best" timing is 2 to 4 degrees below what would be seen as the "optimal" timing. For example, it 16 degrees give you the lowest MAP reading for your idle speed, then I'd aim for 12 to 14 degrees commanded. My reasoning for this is that it allows for better isle RPM management via the idle spark tables.

If the ECM detects a slight drop in idle speed, it will add timing to help pick up the RPM. If the timing is already at optimal, adding timing will have less of an effect compared to if the base timing was a little under optimal. It'll probably idle on anything between 10 to 20 degrees, the quality of the idle you want will determine how much time you want to spend on it.

Simon.

[joecar]

+1 on finding timing that produces the most vacuum (least MAP) and then backing down from there.

[bplumcrazy]

Is their a way to lock timing, mine hunts from around 8-20....... sorry if this is a newb question but I have been reading as much as I can

[Jester]

You can smooth it out by lowering the adaptive idle tables High/Low correction between 16rpm through to 64rpm. This is what I did anyway which was suggested by Hymey or Swingy I think, timing correction smoothed out and at the same time I lost some lope, depends how lumpy you want it to idle. Give that a whirl see if it helps.