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View Full Version : Optimal Idle Timing for cammed LSx


Goldfinger911
October 8th, 2007, 04:14 PM
I was doing some fine tuning of Desired Airflow and VE on my cammed 2002 LS1 yesterday. I made note of what my load was at idle. Then I was using the the LS1 Control panel bi-dir and forcing different timing advances at idle.

I noticed that when my timing dropped, load went up. And then the opposite when I went back to 23 degrees (where I started from) which produces a load of right at 50kPa.

I stopped playing and finished RAFIG. Then changed idle timing and did RAFIG again for Desired Airflow. The isle lead was higher and all of my Desired Airflow Numbers went up (positive numbers in the map.)

My question; would it make sense that optimal timing for a given cam be the advance which produces the least amount of load at idle? Everyone is always trying to improve idle with cammed cars and was wondering if this logic holds true? Wouldnt that indicate that the timing advance than produces the least load, is the one that is producing the highest efficiency at that given RPM, IAC position, etc?

If this is a totally dumb question, oh well. :)
SSbaby
October 8th, 2007, 05:19 PM
I wouldn't think so. I just subtracted 3-4* from my base spark and I would say it's improved the idle quality (less rocking) and off idle driveability (no stumbles).

You don't need to run a huge amount of spark at idle... I run leaner with less timing in preference to running richer with more advance.
Goldfinger911
October 8th, 2007, 05:28 PM
That doesnt necessarily prove my hunch wrong. Change your idle timing back, and forth and watch what happens to idle load. I would love to know which is better. What cam are you running? Specs?
SSbaby
October 8th, 2007, 06:56 PM
That doesnt necessarily prove my hunch wrong. Change your idle timing back, and forth and watch what happens to idle load. I would love to know which is better. What cam are you running? Specs?

Yes more timing reduces load but what I'm saying is that it doesn't translate to 'better'... at least as far as driveability is concerned.

How is a lower MAP necessarily 'better'? It's a balance IMO.

cam is 224/224 110 .570" lift