12 LS3 bolt-on's & cam weird rolling idle dip

[chassis]

This has been bothering me and I thought I understood why but apparently not. I made a log of the car at idle and no throttle input what so ever so you can clearly see what I'm talking about, and on a slight down grade so it would roll. While sitting still it idles where I want it and all is good, soon as it starts rolling it adds timing, TPS goes down and LTFT get wacky while rolling, come to a stop and it returns to normal. I know that the idle timing is different than the main table and the coast down but if I make then match it still loses RPM and thus making for s harder takeoff.
I want to understand why it closes the throttle blade. I'm more or less trying to make it so it will not lose rpm when introducing vehicle speed. My commanded is 900 idle and I sometimes see dips into the high 600's. Not a crazy cam by any means only 5* overlap. I hope someone can make me understand the blade closing and how to stop it.

Thanks guys.

[C5 2000]

First compare your file with stock, then change back to stock Airflow Baro Mult, Throttle Follower Torque, Map A-Normal to stock if touch that table, change Cutoff RPM Hyst to 225 and Dynamic Airflow High RPM Disable to 500 and High RPM Re-enable to 400

[chassis]

So, after doing some more investigation and playing with different scenerios the puzzling thing to me is it will only lose rpm and gain timing if the clutch is in while rolling... If i'm in neautral with the clutch out and rolling it will act completely normal as is when at a stop. Will CFCO mess with this at all?

[mowton]

Add .5 g/sec in 2100-2400 HZ Maf cell and interpolate from 2400 HZ to 2850 to remove dip. This additional request for air will open the Throttle plate a bit more. See if this improves. tweak as needed if improvement is seen.

You can also try and make small changes (i.e .25 g/sec) to the Airflow Final Minimum cells at the rpms where the airflow drops if the MAF changes doesn't help.

Ed M

[chassis]

Hey Ed and thanks for chiming in. I thought I had this licked that last time we talked but to no avail I still have the issue. The confusing thing among most of these gremlins is that it will only do this while the clutch is in, when out and in neutral it will not.... So if it was MAf or BRAF related why would it be acting this way only when clutched?

[mowton]

Hey Ed and thanks for chiming in. I thought I had this licked that last time we talked but to no avail I still have the issue. The confusing thing among most of these gremlins is that it will only do this while the clutch is in, when out and in neutral it will not.... So if it was MAf or BRAF related why would it be acting this way only when clutched?

Your welcome. My thinking is, with the clutch in you don't have the tranny/car load storing any inertia......free wheeling if you will. Completely different animal to the pcm. I recommended the maf/raf with the understanding that the throttle was closing from dead stop (adaptive idle) to slight movement (same load, different throttle setting) transition. The maf looked a b it low in those areas anyway.

Ed M

[chassis]

I'll try it this afternoon and report back. Thank you.

[mowton]

I am comparing 2 new era files, one from October with a ...(2) suffix and the one you posted here. There is no difference in the MAF or MIN Idle Airflow tables in the area's I have mentioned above and which we discussed the last time. Are these the correct files too compare? The one posted above is what is in the car now, correct? Try it and see what happens.

Ed M

[chassis]

No, I just made a copy and made changes to the MAF and BRAF. Here it is.

[chassis]

No such luck with the maf and braf change. I even added more to the second tune to see it it would swing any but still the same. The second scan is plus another .50 to the maf and plus .25 to braf.

[mowton]

OK, try this, set the High Octane timing table to 23 from .12 to .32 g/cyl and 0 to 1000 rpm. if no help then try taking out the min air and maf changes...after that??????? :-) Lets see.

Ed M

[MikeOD]

OK, try this, set the High Octane timing table to 23 from .12 to .32 g/cyl and 0 to 1000 rpm. if no help then try taking out the min air and maf changes...after that??????? :-) Lets see.

Ed M

Don't do that, that's not why the timing is changing.

Look at Engine - Spark - Advance - Idle Adaptive Spark Control.

If you open those 6 tables, you'll see that the over and under adaptive controls are different for drive vs neutral in both coastdown tables.

The pcm switches to coastdown "drive" when your foot is on the clutch and off the throttle and rolling above a MPH threshold (I believe it's the adaptive idle RPM VSS and Hysteresis under Engine - Idle - RPM, which would total 2.4). That's why your problem goes away when you put the shifter in neutral and take your foot off the clutch, when you take your foot off the clutch it switches back to coastdown "neutral".

So, to solve your problem, put everything back to exactly what it was in the first file you posted to this thread, and then open up the Engine - Spark - Advance - Idle Adaptive Spark Control Overspeed and Underspeed tables, and in each table, copy what you see in neutral to drive.

Check the before and after pictures below. Should fix your problem immediately.

[mowton]

Don't do that, that's not why the timing is changing.

Look at Engine - Spark - Advance - Idle Adaptive Spark Control.

If you open those 6 tables, you'll see that the over and under adaptive controls are different for drive vs neutral in both coastdown tables.

The pcm switches to coastdown "drive" when your foot is on the clutch and off the throttle and rolling above a MPH threshold (I believe it's the adaptive idle RPM VSS and Hysteresis under Engine - Idle - RPM, which would total 2.4). That's why your problem goes away when you put the shifter in neutral and take your foot off the clutch, when you take your foot off the clutch it switches back to coastdown "neutral".

So, to solve your problem, put everything back to exactly what it was in the first file you posted to this thread, and then open up the Engine - Spark - Advance - Idle Adaptive Spark Control Overspeed and Underspeed tables, and in each table, copy what you see in neutral to drive.

Check the before and after pictures below. Should fix your problem immediately.

Mike interesting and look forward to Bills update. The issue though doesn't seem to be in coast down (per the logs), rather when he hits 0 mph per the logs I have looked at. The coast down is adding timing and seems to be holding. Maybe I just have just looked at this too much :-) So I will relinquish to another set of eyes.....

Ed M

[MikeOD]

Mike interesting and look forward to Bills update. The issue though doesn't seem to be in coast down (per the logs), rather when he hits 0 mph per the logs I have looked at. The coast down is adding timing and seems to be holding. Maybe I just have just looked at this too much :-) So I will relinquish to another set of eyes.....

Ed M

I'm basing my reply on this.

I made a log of the car at idle and no throttle input what so ever so you can clearly see what I'm talking about, and on a slight down grade so it would roll. While sitting still it idles where I want it and all is good, soon as it starts rolling it adds timing, TPS goes down and LTFT get wacky while rolling, come to a stop and it returns to normal.

I'm more or less trying to make it so it will not lose rpm when introducing vehicle speed.

So, after doing some more investigation and playing with different scenerios the puzzling thing to me is it will only lose rpm and gain timing if the clutch is in while rolling... If i'm in neautral with the clutch out and rolling it will act completely normal as is when at a stop. Will CFCO mess with this at all?

Also, you have CFCO disabled already...I think it was disabled stock in the Camaro LS3 program. Mine was.

[chassis]

I will give that a shot and let you know what happens. Thanks Mike. Thank you too Ed for your help thus far.

Are you getting snow up there in CT yet Milke? I lived there for 30 yrs before I moved to NC. Don't miss the snow!!

[MikeOD]

The forecast says we're going to get a small amount of snow tonight...guess that means my car is going to sleep until April.

[chassis]

Been there...

[mowton]

South Florida........Sunny and 80, sorry guys. This is our first winter in the sunny state, retired in March and moved here with wife in September. Won't say I'll miss the shoveling of snow like last year on Long Island.....

Ed M

[chassis]

Thanks for rubbing it in Ed!! Can't say I blame you from moving off the island. Finally getting cool weather here, car is running like Jack the bear! Now to get that damn idle issue figured out......

[chassis]

Ok. Frustration has finally set it. Still no difference.........