idle spark advance vs idle airflow
10-15-2005, 03:41 PM
#1
idle spark advance vs idle airflow It occured to me last night while adding spark to get rid of bucking that adjusting my idle spark tables might require me to retune my idle airflow tables because i wanted to keep the idle & main spark tables the same in that area. Well after a little experimenting here is what I came up with. The effect of spark on idle airflow is much bigger than I imagined it would be.
Conclusions:
- If you change your idle spark tables you will probably have to change your RAF tables too
- You may be able to save some gas by bumping up your idle spark
If anyone wants to try this themselves (with hptuners 1.7), do this. Let your car warm up to full temp and start logging with spark advance and dynamic airflow pids. While logging go to tools>vcm controls>fuel & spark>spark control. Click on the absolute box so it turns green, then use the arrows to run through a range of spark advance ( i did about 15 to 49 or so). Make the timing changes slowly enough that the pcm doesn't have to play catch-up with the iac (about 1 degree every couple seconds is fine). Click the absolute box when your done to go back to normal spark advance. Save your log file, export it to a csv file, import it into excel, and plot advance vs dynamic airflow.
Conclusions:
- If you change your idle spark tables you will probably have to change your RAF tables too
- You may be able to save some gas by bumping up your idle spark
If anyone wants to try this themselves (with hptuners 1.7), do this. Let your car warm up to full temp and start logging with spark advance and dynamic airflow pids. While logging go to tools>vcm controls>fuel & spark>spark control. Click on the absolute box so it turns green, then use the arrows to run through a range of spark advance ( i did about 15 to 49 or so). Make the timing changes slowly enough that the pcm doesn't have to play catch-up with the iac (about 1 degree every couple seconds is fine). Click the absolute box when your done to go back to normal spark advance. Save your log file, export it to a csv file, import it into excel, and plot advance vs dynamic airflow.
Last edited by P Mack; 08-04-2007 at 10:51 AM.
