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View Full Version : What is reasonable timing swing @ idle?



Chalky
August 2nd, 2007, 02:06 PM
Trying to smooth out idle after doing RAFIG today. I logged timing and some airflow pids but noticed that my timing is constantly swinging. Extremes seem to be from approx 22* to 35*. I obviously have some idle hunting as well along. Car is cammed with headers and AFR heads.

Do these timing swings seem reasonable?

SSpdDmon
August 2nd, 2007, 02:24 PM
My tune has the base spark set to 22* for 800rpm and 22.5* for 1200rpm with a desired idle speed of 850. Here's a random section of idle from my log earlier this evening.

Based on this, I'd say +/- 4* is normal.

Chalky
August 2nd, 2007, 02:51 PM
I am looking at your tun you sent me recently. Our VE tables are similar but I notice your lower rmp/KPA cells are quite a bit leaning than mine.

Our timing tables are similar with mine just carry a bit more advance in the 800-1200 rpm ranges.

I may just setup some timing pids tomorrow and see what is affecting my timing to the degree that it does.

Maybe I need a couple more cycles of driving to see if it smooths out.

I may try adding soem more air via TF tomorrow to see what it does to the slight off idle stumble and slight surging I see @ 1400-1600 rpm when crusing in 4th.

SSpdDmon
August 2nd, 2007, 02:55 PM
I am looking at your tun you sent me recently. Our VE tables are similar but I notice your lower rmp/KPA cells are quite a bit leaning than mine.

Our timing tables are similar with mine just carry a bit more advance in the 800-1200 rpm ranges.

I may just setup some timing pids tomorrow and see what is affecting my timing to the degree that it does.

Maybe I need a couple more cycles of driving to see if it smooths out.

I may try adding soem more air via TF tomorrow to see what it does to the slight off idle stumble and slight surging I see @ 1400-1600 rpm when crusing in 4th.
My cam will be more inefficient down low than yours, which is why you'll have a little more fuel down low.

If the throttle follower doesn't cut it and AFR is in line, you may have too much timing.

As for the timing swing, how do my Spark>Idle>Overspeed and Underspeed tables compare to what you have?

What about the Idle>Learning>Learned Airflow and Desired Airflow tables? Do you have values in the 20rpm row?

Chalky
August 2nd, 2007, 03:17 PM
Des Airflow is similar within .3 tenths

Learned Airflow Correction still has entries in 20-40 rpm rows.

Idle overspeed is same.
Idle underspeed error you have 9* @-300, I have 0*
@-250, you have -9*, I have 0*
@-200, you have 9*, i have 4*

In Learned Airflow Corr, you have more airflow @ 20 & 40 RPM of .000977

Correction: Just sent my tun to you. There are quite a few differences. Might be easier to do compare in EFILive

SSpdDmon
August 3rd, 2007, 01:46 AM
I'll look at it later this weekend. I have a certification exam in 2 hours and then we're going to the track tonight. :)