I got bored today and decided to see what the tables labeled Idle overspeed spark retard error and idle underspeed spark advance error in the newest Tunercat def. file did if I "0" out the tables. My guess was it would stop the spark advance at idle from fluctuating around so sparatically and help smooth out the idle some. My findings were exactly that! Idle spark advance is stuck at 30 degrees, doesnt move a degree either way and the idle rpm does NOT surge like I thought it might. Anyway, I just thought Id pass that along in case nobody else noticed the tables and their effects.

 

the spark idle fluctuation is is almsot like a secondary IAC. On LS cars it always seems to help idle stability rarely does it help when I disable it. On LT1 cars it may/may not be the same way. ill have to play with it some

 

Interesting. I was wondering why it did this today. I was thinking it was a vacuum leak or slight miss, etc. My thoughts on a solution on this would be setting the "Individual Cylinder Fuel Trim (at Idle)" all to "1"? Cylinders 1,3,5,7 are not at "1", so could this also be a solution to smooth out the idle? Has anyone else attempted this.

Ryan

 

anymore commentary on this? i could use a smoother idle with my lopey cam.

 

I tried removing the overspeed and underspeed spark adjustments and my idle was A LOT worse... I put them back in and idle smoothed out.

In regards to surging, I've adjusted my Idle spark advance until I got it high enough that the surging would go away. The only issue I had with increasing it too much was the car would generate a lot more heat at idle. Cruising Woodward last week, I dropped it a few degrees just of the day... as it took about 2-3 hours to drive a few miles.

For regular driving, I've slowly moved Closed TPS Spark advance down until the surging started again and increased it one degree. For my combo... 23 degrees at idle feels good and I set it from 0 up to 1200rpm as I have a high idle to smooth out the lumpy cam.

 

Cman is your idle steady or does it jump all over the place like mine? I have mine set at 900 but it is constantly jumping around in the 775-900rpm range.

 

Just quote from another post I made:
I tried playing around with the over/underspeed spark. I removed it completely, and also tried removing it for small idle fluctuations... and interesting enough... my idle got WORSE as it couldn't compensate as quickly. I think with a lumpy cam... allowing the computer to adjust timing is necessary to keep it as smooth as possible.

To minimize how much "work" the computer needs to do, I actually found that when I trying to determine my closed TPS timing, I'd set a specific timing... and then would watch how the computer adjusted it on it's own. If it tried to always adjust it up... I would reprogram it at a higher spark advance. If it seemed to drop more than go up, I tuned down. Once I got to the point where the over and underspeed fluctuations were about equal... I knew I was close to the "sweet spot" for the car. I also used my MAP levels as well as general driving in Drive and Park at different temperatures to fine tune it even more. I do change it once in a while... in the middle of the summer versus in the spring/fall, and this year when cruising Woodward where the car would idle for hours in stop/go traffic, I'd remove a little timing as the car stayed cooler that way.

BTW... C_Rules... I got your PM and will try to answer you l8r tonite.

 

so would you say that your rpms at idle are pretty steady now that you found the proper closed tps idle spark. about how much fluctuation from your set idle are you getting?