Idle tuning -- timing

[heavyfoot]

I've got a 99 M6 car that only has stock MAF, LS6 intake, 2.02 heads, 224/224 cam, headers and exhaust. I have performed auto VE tune however instead of remaining in speed density I have returned to MAFcontrol.

Before and after auto VE tune I have been having cold idle/surging issues. After auto ve tune the problem is worse. When outside temps is ~70 deg F, with car cold. IAC counts will start at ~120 then move to around 65 as car warms up. If I touch throttle at all car starts suring badly and will stall. Someone suggested bumping up timing. I'm seeing around 13-20 Deg of timing when car is idleing. I set the 4 primary tables (high octane spark map, low octane spark map, base spark in park/neutral and base spark in gear). I have set all the associate airflow and rpm cells for idleing to 28 deg. The car still will idle around 13-20 Deg of timing.

Can anyone direct me to the idle timing tables. I search and found many different timing tables that all "ADD" together to come up with a timing value. How do I troubleshoot this issue.
thanks,

[Tordne]

Surging is often a side effect of airflow as well. Check the Throttle Cracker and Follower tables, and also the decay rates. You may find that the Throttle Follower airflow is being decayed too quickly. Also check the Desired airflow table as this can effect idle quality as well... Do you find the RPM dips when you are costing and push the clutch in?

[TAQuickness]

Also, before you start changing your tables, use the BiDi to determine the optimum AFR/Spark combo for your engine. You'll be looking for the combo that produces the most vacuum.

[Tordne]

I found that changing spark etc with the Bi-Di controls seems to make the car surge. Yet commanding a particular spark value in the tables works fine :nixweiss:

[TAQuickness]

I found that changing spark etc with the Bi-Di controls seems to make the car surge. Yet commanding a particular spark value in the tables works fine :nixweiss:

Where you using the delta spark or actual spark? Delta spark is the key for me.

[Tordne]

Can't remember to be honest it was a while ago. Next time I'll buy the RoadRunner and have real BiDi ;)

[oztracktuning]

I use the delta with no issue. i think the surge is caused by the cam and inconsistent fuelling. The bidi delta turns idle spark correction off when activated and that is what is stopping it from surging.

[Doc]

I second the fueling line of thinking.

[heavyfoot]

thanks for replies guys. I tried using bidi before but I think I was using actual. I commanded 28 deg. and it idled great but as soon as I turned the bidi off the car reverted to ~20 deg. it surged then died. I'll try using the delta. And yes the car will dip when I push the clutch in. Let's see that should be the throttle follower...correct?

[TAQuickness]

If you are at a stationary idle, and all you do is push the clutch in and it dies, it's not related to the follower or cracker.

Problem there is you changed the load on the engine and it couldn't compensate fast enough. Sounds like the problem is in your base timing tables. As you noted above, at 28*, car idled good, but at 20 it would surge and die. You should try raising your base spark tables a bit.

[heavyfoot]

Well I tried that. I set the base spark in gear and base spark in park/neutral all cells in the low map region and rpm region to 28. However on a cold start the car still idles around 20 deg. Once the car is up to temp it starts using the base spark in gear table and the spark would go to 28. I do not have any idle issues once car is warm, just when it is cold started.

[SSpdDmon]

Well I tried that. I set the base spark in gear and base spark in park/neutral all cells in the low map region and rpm region to 28. However on a cold start the car still idles around 20 deg. Once the car is up to temp it starts using the base spark in gear table and the spark would go to 28. I do not have any idle issues once car is warm, just when it is cold started.

{B5910} is probably subtracting timing... ;)

[heavyfoot]

The car does not dip when I'm at a stationary idle. It only seems to dip when I'm rolling and push the clutch in.

What spark table is used when the car is started cold and as it warms? Once it's upto temp then it seems to begin using the Base Spark In Gear table. While car is warming if I bump the throttle I'll see it begin using the Base Spark in Gear table for a few seconds. As soon as I let off the throttle. It will hold to 28 deg. for a seond or so then it will go back to ~20 deg.

[oztracktuning]

Up your rolling idle rpm but most likely ist idle air thats not high enough. Make sure the car lowers in rpm when you stop - get idle air high enough to make it hang just a little rather than do what its doing now - its hanging low.

[SSpdDmon]

The car does not dip when I'm at a stationary idle. It only seems to dip when I'm rolling and push the clutch in.

What spark table is used when the car is started cold and as it warms? Once it's upto temp then it seems to begin using the Base Spark In Gear table. While car is warming if I bump the throttle I'll see it begin using the Base Spark in Gear table for a few seconds. As soon as I let off the throttle. It will hold to 28 deg. for a seond or so then it will go back to ~20 deg.
The base and high/low tables are what's used at all times. There are adders/subtracters that are applied to these tables for various conditions (ie - colder ECT's). You need to log several of the spark .pids during a cold start to see which ones are adding/subtracting so you know which table to adjust.

[heavyfoot]

will do...thx