Strange throttle surge, Not tune?

[outcastdon]

Hello all,
I have almost always read and received good advice and tips on this forum.
But have not had the need to ask many questions or the need for advice, until now.
Currently doing VE tuning but reoccurring no matter what.

2003 C5 Corvette Z06, 6 speed
406 LS3, CNC built block, AFR 230 Mongoose heads, about 11.3 to 1 compression
FAST intake, Ported 90mm TB, Comp Cam, 615 lift intake and exhaust, 242-250 duration
2110 Johnson lifters with Manton pushrods. Currently with Volvo injectors 9186340.

Situation: Have had the same "problem" with 2 different engines, formerly with 392ci, 3 different cams, 2 smaller ones with less overlap.
At cruise, part throttle, between 11% to maybe 16% registered, there is a fast surge or stutter. It might show up in the attached log.
Around 1500 or so rpm's. The rpm's jump up 100 to 200, immediately, without warning, and will not go away without modulating the pedal.
No air leaks, as I have checked various ways, intake off, air cleaner assembly apart and reinstalled a few times. Smoke test, carb cleaner, ect....
Have had same situation with different injectors, also.
TB, TAC, Pedal problem??

I still consider myself a newbie, especially with the newest version of HP Tuners.

Any comments or suggestions greatly appreciated.

[kevin87turbot]

There are several things going on with it that is contributing towards the issue. It's running pretty rich...according to both the wideband and the narrowband sensors.
That needs to be addressed.

After that, you can disable the throttle cracker tables and it'll likely fix the surging issue.

[Mr.z0611]

Smooth your main VE as well. It's way off

[outcastdon]

Thanks for the replies.
Was in process of doing the VE tables. But the problem has happened with the other engine tuned before.
Will go over the tune more as weather here permits, raining like hell.
As far as disable the cracker. Completely?

[Mr.z0611]

The ETC area scalar is not right as well. Ported to what size?

[outcastdon]

The ETC area scalar is not right as well. Ported to what size?

Just smoothed to edges by former co-worker. Same plate. Scalar is as other tune on different engine and seems close to stock 90mm would on Gen 3. .192?

[Mr.z0611]

I searched for a stock z06 in the tune repository with the same OS number as yours and it's 0.0255

[outcastdon]

I searched for a stock z06 in the tune repository with the same OS number as yours and it's 0.0255

Yes, that is for the stock TB. I have a LS2 90mm

[village_idiot]

The idle, and base timing tables are very erratic in that rpm range in this tune. I would start with working on those tables

[outcastdon]

The idle, and base timing tables are very erratic in that rpm range in this tune. I would start with working on those tables

Thank you. I will. Want to drive it but can't at the moment.

Keep the suggestions coming. As this has happened in a few iterations.

[outcastdon]

Thank you. I will. Want to drive it but can't at the moment.

Keep the suggestions coming. As this has happened in a few iterations.

Checked tune's spark tables, high, low octane and Idle advance park and drive, all match.

[outcastdon]

Anyone else got ideas?
I may get to drive it today.
Willtry to repost new tune and log later.

[outcastdon]

So, today I merged the 406 tune with part of an old 408 tune from a previously installed engine. Did not change much.
Still having stutter under 2000 rpm with between 12.5% and 15% throttle. No matter the speed of the vehicle.
Yes, I must retune for the VE table but using the bi directional controls while driving, and focusing on the places where the stutter occurs,
could not remove it or decrease it using a richer or leaner AFR or using higher or lower timing. Usually doing this in a straight, slightly downhill area of highway to stay in the same throttle percentage.
Stoich AFR is set at 14.47. A couple of tunes ago was set at 14.27 and seemed not to stutter as much.
Still wondering about the TB and/or TAC, and/or the pedal sensor as it has done this for a while.
Please help.