2007 C6 Z06 Idle Timing Advice Needed

[rio95]

I've been spending some time idle tuning my 2007 C6 Z06 with heads, large cam, intake, and exhaust. It idles very stable with stock timing and airflow, but I get some dipping (doesn't usually stall but has) with the AC on in hot weather. The only other issue I'm having is my low idle vacuum seems to affect my braking at times.

My VE and MAF tables are fully tuned and fuel trims are good. I started my idle tuning by trying out different idle timing and was pleased to find that I could increase idle vacuum by adding timing. I was surprised to find that as I added timing, the car would surge more with adaptive idle turned off (almost stall). So should I strive for better vacuum or more stable idle? I'm struggling to decide what the optimal idle timing is for my car.

All the numbers in these tables are averages over a 60 second period.



These table show the standard deviation for RPM, MAP, and idle adapt advance. You can see that the variation for all three increases as I add timing, BUT like I said, more timing is giving me more vacuum. Should increasing the idle airflow on the tunes with more idle timing reduce the variation/surging? If so, maybe I should run 18-20 deg and tune the airflow table. Thoughts?



Once I decide on what timing to use I think I can fix my dipping issue by tweaking the airflow table or disabling CFCO. I'm just not sure what timing I should run.

Here are my tunes and scans for the stock timing and 12 deg added.

added 12deg.hpladded 12deg.hptstock timing.hplstock timing.hpt

[MikeOD]

Just a thought...increase the idle RPM a little to get some more vacuum out of the engine? I wouldn't run too much advance because it leaves nothing "in reserve"...on the gen 4 stuff I usually try to stay at 17 degrees or a little lower.

[rio95]

Just a thought...increase the idle RPM a little to get some more vacuum out of the engine? I wouldn't run too much advance because it leaves nothing "in reserve"...on the gen 4 stuff I usually try to stay at 17 degrees or a little lower.

Funny you say 17, because that is exactly what I used while playing with idle airflow today. As seen above, my vacuum was increasing all the way up to 25 degrees where I stopped (I bet it'd keep increasing) so I think I have plenty of reserve.

If I can't fix my dipping with idle airflow I'll try bumping the idle like you suggested. I've got to ask some questions about idle airflow over in that "towel" thread.....