LS3 in C5Z Low rpm bucking Help

Well,

I just had an LS3 transplanted into my C5Z. The car was dyno tuned after the motor was built and the builder only did an idle tune. On the dyno, the motor was run in and part throttle/WOT was tuned and the engine made 468/430 at the wheels. When I got the car back, the car drove fine at cruise, however the way it behaved at traffic speeds was horrible. It bucks very hard under 1600rpm or so, above its smooth as glass, below a nightmare. I had made some attempts to clean up the VE table around that area, but its not helping too much. I need some help please :worship:

Specs are as follows: 0411PCM
-Stock LS3 bottom End
-GMPP LS3 Ported heads
-Ported 90mm LS2 throttle body
-custom grind COMP 226/238 @113+1 Cam
-KN FPIK intake for LS1/6, stock 84mm maf
-ARH 1-3/4" headers,

I am logging AFR through an Innovate LC2 WB and EGR. I have provided the math parameters that let you see the AFR logs.

Please guys any help is appreciated. I'm attaching the tune I received with the car, as well as where I got to with the airflow tuning.
Thanks

P.S. there is also a spot between 4000-5000rpm at low throttle angles where the car feels like it hits fuel cut and the AFR goes super lean.

Are you positive that it's fully in speed density mode for the logs right now?

The MAF dtc's aren't set to MIL on first error like they should be. Also logging the MAF channels can skew your data when you apply the error changes to the VE. You can log the MAF sensor status to make sure it's running in speed density too.

The Log 5-29-18-1 should be fully in speed density.

The tune "LS3 C5Z06 5deg...." is the tune currently in the car that should be SD only

I'm going off this guide
http://ls1tuningguide.com/tuningmanu...structions.pdf

Look at Engine Diagnostics---DTC's---P0101,102,102. They are set to Mil on second error. All three should be Mil on first error. Uncheck the boxes if you don't want the error light. I didn't look at the maf but it should be failed 1 and 2

OK lets start this again.
I've made some tweaks to the VE table following the guide above. Maf hopefully failed.
The mid 1000RPM bucking is pretty much gone, however I still have some bucking at parking lot speeds. It seems to get worse with coolant temperature.

The car has a ported 90mm throttle body, and the tuner set the ETC scalar to .0302 instead of the .0192 that I've seen with switching the 78mm tb to 90mm.
following the LS1 tuning guide throttle body scalar calculator, I've adjusted it to .0156 and the car won't start. I'm not certain what airflow tables I need to modify to get it to actually start.

Help please?

looks to be super lean down low at high MAP and your 1300-1700rpm region. narrow band mv at 72mv tells me its lean. lean will cause surge.

turn on closed loop and listen to your STFT or use a wideband to clean up your low RPM AFR. don't be afraid to run on the ricj side of stoich down low with a decent cam.

you could also populate your rolling idle RPM table with data that matches your target idle table.

using a constant spark value from 1600rpm down in both idle spark tables and copying the data from 1600rpm down into main spark tables can help you to tune idle fueling, without the spark confusing change you.

by your data log id be fixing low RPM AFR and idle fueling before moving onto airflow tables or making drastic timing changes.

remember STFT at idle can be quite misleading when you have a camshaft with decent duration on overlap on a tightish LSA

ONCE MORE.


I've been searching and reading the various threads on here to get to the bottom of this. Currently, I've played with the injection timing to get it into a range that I believe I've reduced or eliminated fuel short circuiting.
After that I moved onto Airflow, tuning the VE table finding best timing at idle, where I used the MAP values and IPWs to see if my timing changes were good (seemed like it liked 30* timing). Then I tuned the RAF where it pulled like 30% from where I had it before.

I've moved onto tuning the cracker and follower tables. When in SD mode with STFT turned on, the car drove mostly nice, except around 1000-1500 RPM where it would start bucking, as I went into the throttle to accelerate. It would do the same thing sweeping back down through the RPMs. I also get a bit of a dip when taking off from a stop where its difficult to maintain RPMs as I come off the clutch.

AC seems to be another issue. The car runs almost perfect with the AC off but bogs, hesitates and bucks with the AC on.

Since I made this post, a few changes have happened;
The car now has an LS7 card maf and C6Z06 stock intake setup, and a ported and radius modded intake manifold.
I don't think I have any issues per se with the card maf, it seems to work fine.

I'm attaching a couple of files, the tune, a log in SD closed loop, and a log with mixed model but open loop. The mixed model one was meant to be MAF only... :doh:

Many thanks for the help.

How is your pcv hooked up/routed? how is your maf installed? distance and orientation from throttle body? your MAF curve is pretty rough. VE looks decently smooth but if its based off any abnormal vacuum/exhaust leaks then nothing is gonna jive. I dont have a stock file to compare, so revisit your idle PID settings and make sure they arent drastically altered. a larger TB does require tuning, but you dont have to change a ton of stuff. when that blade swings it moves alot of air, so dont let it dance around. and if the MAF is to close to it, or not positioned properly, then it'll compound the issues. those slotted MAFs are sensitive. dont mount it upside down, and make sure its atleast 10" away from the throttle plate. when you are in SD make sure your high rpm disable is set higher than the range you are gonna tune in. you have it set to 4K.
you gotta alot going on with the engine. alot of alterations. make sure you have good terminal crimps/soldering on your wiring connections/ grounds/etc. (especially where the ls2 throttle body was installed)............