AFR's at idle

[NoDOHC]

Originally Posted by NoDOHC

Ignition Timing (BTDC) Manifold Pressure at Idle (kPA relative) Idle AFR
20 -75 to -80 12.2-12.7 *These are very close
15 -70 to -75 12.5-13.0 *These are also very close
10 -65 to -70 12.8-13.2 *More of an estimate on the AFR, vacuum is right
5 -60 to -65 13.0-13.5 *Pretty accurate (ran for a while at this)
0 -55 to -60 13.4-13.8 *Ran for a few minutes only
-5 -50 to -55 13.7-14.4 *Ran for weeks
-10 -45 to -50 14.4-15.0 *Was running at 14.8, closed loop until my fuel system gave up the ghost from the E85.

Please allow me to correct some misinformation here. These numbers were taken using my old AEM wideband.

A new, calibrated Haltech wideband is now indicating that my AFRs were not stoic as I originally thought.

The table above should actually read more like this:
Ignition Timing (BTDC) Manifold Pressure at Idle (kPA relative) Idle AFR
20 -70 to -75 12.4-12.6
15 -66 to -70 12.6-12.9
10 -62 to -66 12.9-13.1
5 -58 to -62 13.1-13.2
0 -53 to -58 13.2-13.3
-5 -49 to -53 13.4-13.6
-10 -45 to -49 13.8-14.0

I tried retarding the timing more, but the AFR had to actually go richer again as I went in that direction.

This is all taken at 700 RPM (my new idle). I was idling at about 1,000 rpm before, but I got tired of waiting for the trans to stop to use reverse.

Advancing the timing past 20 degrees didn't really increase the manifold vacuum any, nor did I see any changes in the AFR (went from 20 to 40 degrees with no noticeable change.
The engine will idle at stoic, but it misfired every 2 seconds or so (very annoying).

I apologize for the misinformation, it was correct to the best of my knowledge.

Originally Posted by TitaniumTT

porting plays a HUGE role in that as well

Correct you are!

I should list my porting - stock port timing (open/close), slightly cleaned up.